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AUNT EM'S PROBLEM PAGE

Aunt Em is here to try to provide answers to the questions that experts generally take for granted, leaving the novice floundering because basic building

blocks of understanding are missing. Aunt Em is always glad to be corrected or to get extra info from smart Alecs.

17.5 Home Talkie/Pathé Natan

(This is an edited version of a longer and more diffuse exchange)

Q. I recently acquired a 17.5 Pathé Natan (much the same as the UK Home Talkie). I threaded it up and hand cranked it to watch and see what everything does, and where everything goes, etc. I did this for a while so I felt confident and turned it on. Everything ran smoothly, but YIKES! That thing is moving so fast it scared the bejaybbers out of me. Even if it was running perfectly, it looks like one of the scariest projectors ever, with the slightly offset path through the gate, and the frightening GEM/SON wrap around the body of the machine, and then the sharp turn straight up to the take up, and the crazy sound slide thingy that looks like it scrapes the film? Or does it look scarier than it is?

Now I find it is losing the loops almost as soon as I turn it on. I am perplexed, as I feel like I am threading the machine correctly. I can turn it by hand all day and it runs beautifully, but as soon as I start the motor it almost immediately loses the bottom loop, and then somewhat quickly loses the top. I try to see where things are going crazy and the closest thing I can see is the gate area seems to have more movement than I have seen on other projectors. What I mean by this is the back plate of the gate that is attached to the lamp housing, seems to almost be bouncing around. Does this seem normal?

I am first thinking about replacing the screw just beneath the gate area with one that I can screw in with a roller on it, so it won't lose the bottom loop, especially since that is the harder of the 2 to watch easily (the top one I can see as it is disappearing).

A.  I don't see how a roller stops it losing the loop. All it will do, surely, is to in effect make the loop smaller, with less slack before it catches on something - unless you have in mind an auto loop former? - so that it gets lost even quicker?

The correct way is to get the film and projector in good order and thread it correctly. Don't forget that these machines managed to work OK for some years in the hands of God knows who - they will work if treated properly.

With the Natan/Home Talkie, the threading around the sprocket is critical. You put the "top" (in this case lower) loop in place, but then you have to open the same set of rollers again to thread the "bottom" (higher) loop thru. It's easy for the "top" loop to slip out and as there is no loop worth speaking off, huge damage occurs at once. However, I have found that so long as the film is in perfect repair, it will go thru fine if you get the threading right. But don't trust it an inch - watch the machine, not the picture!

There are details somewhere on Cinerdistan of a device I developed for providing movement of the sound chute during projection - normally you can only adjust it when there is no film in the chute. I did this 'cos I had quite a problem with a wandering sound track on Lorna Doone -  kept getting that snoring noise from time to time as something other than the track got scanned, with no way to correct it. Despite looking scary, the chute does not seem to do any damage; note that the instruction book makes clear the chute must be fully closed with the film bowed.

The back gate should be fixed to the projector by 2 small screws, one visible above the gate, the other you need to take the lens off to see - easiest to adjust this one with the screwdriver thru the nozzle at the front of the lens housing. If either of these is loose, it could affect the gate. Make sure they are tight, but with care - not a lot of thread to play with. The screws have to be v. short so as not to protrude thru the gate - may need a washer or 2 under the head. There is a bit of adjustment for framing.

Of course, if someone has been careless in the past and stripped either or both the threads, we have a problem of a different order.

Q. I did just notice something that may be part of the problem. The bottom roller on the one sprocket wheel does not seem to keep the film tight against anything. I noticed that even with everything all threaded up I was able to slip and slide the film that is entering the gate as if it were not even one the sprockets, perhaps it is simply slipping off the sprockets. I looked at your pictures, and while yours does not seem to be completely pressed up against the sprocket wheel, I am guessing there is just enough space so that when the film is there it is touching. I checked the hole the pivot arm clicks into and it does not seem to be worn at all, but there definitely seems to be too much play between the sprocket wheel and the rollers. I’ve included some pix.

I think I have at least figured out why the top loop is being lost. After much watching, hand cranking, and very brief motor running it appears that the bottom loop is in fact the one going away, then because of the slip the top starts vanishing. My best guess is that the film must be just shrunken enough so as to not reach the sprocket causing it to slip before heading up to the take up reel.  I am guessing that it has about a total of 2 - 3 sprockets worth of play before the loop is entirely eliminated, and once it misses that first sprocket, it is done for. My question then becomes is there a way to avoid this or compensate somehow? It seems to have something to do with the speed as well, because I can hand crank the same section and it won't slip. Is it possible that when things are moving along fast the rollers are not making as tight a connection? Maddening.

 

A. OK, leave us look at this logically. If you are losing the bottom loop, this means one of two things:-

1) The film is entering the loop slower than it is leaving, so we have a gate/top sprocket issue;

2) The film is leaving the bottom loop faster than it is coming in, so it’s a bottom sprocket /take-up problem.

Stans Treason, dunnit?

I suspect 2) so let's start there.

There are three possible projector problems I can think of (at the moment I am leaving out shrunken film ‘cos I have never had a problem):-

a) sprocket retainer roller not close enough to sprocket or slack and can move up and down in relation to the sprocket, or misaligned laterally in relation to the sprocket;

b) belt too tight;

c) clutch tension too great.

In b) & c), the problem may be compounded by a), or in a severe case may even just pull the film thru despite the rollers being positioned correctly.

I have in front of me, even as we speak, two patterns of take-up clutch (see pic). The spring one is obvious. The second may have a problem with old, solidified lubricant, so just needs taking apart and complete cleaning. I can't recall, but there may be springs under the outer big washer. Belt tension I assume you can deal with.

A bent spool scraping the side of the film intermittently might contribute to the problem.

Returning to a), the retaining rollers, any problem here can affect the lower loop at either end. The projector’s front main casting, by which I mean the one to which the rollers are fixed, is pretty soft metal and I have found that the holes may enlarge, not least the two holes relevant here, ie those for  the pivot and the spring-loaded locating pin. I have seen machines with these sleeved up to make up for excess wear. I think on one machine I had to sleeve up AND make a new pivot bolt with a different thread as the old one was no longer fittable.

Obviously, if the locating pin hole has enlarged, the rollers will not be held correctly to the sprocket, so when the machine picks up speed...........

Turning to 1), the gate/sprocket issue, part of this we have already covered above. However, the adjustment of the gate is important. There is usually some small scope for lateral adjustment of the front, fixed gate, as well as vertical for framing. It's important to ensure the sprung gate can move freely when in the closed position. Shut the gate, then push with your finger at the top and bottom, against the gate springs; there should be no grating or sticking against the sides of the fixed portion. As mentioned, the fixed gate may have a bit of adjustment, tho' care is needed to avoid getting the film in a position here the claw does not enter the film cleanly. The lamphouse pivot can also come into play - thin washers either side of the pivot lug at the bottom of the lamphouse may have a role.

Moreover, looking at yore pic (see attached), it seems to me the surfaces pointed out in green should be in contact with those marked red, separated by at most a film-and-a-bit-for-splices-maybe thickness AND unable to move from there. You say the locating pin is firm? Is the pivot firm? Just where is the slack between rollers and sprocket coming from?

Hopefully the foregoing will give you scope to identify the exact nature of the problem. Then we have to move on to a solution.

Eumig Mark S

Q. Just been having a very enjoyable browse around your site, which I came across as a result of searching for info on a Eumig Mark S projector.  I haven’t yet received the machine, but I’m anticipating the need to overhaul it before use.   

I was wondering therefore if you might have a circuit diagram for the amplifier that you might be kind enough to let me have a copy of.  I have a few years under the belt with steam radio restoration so I don’t anticipate too many problems, but it’s helpful to have a map before you set off! 

Strangely, the need for a Standard 8 sound machine originated with a print of “The Telegoons” I was lucky enough to find; something I’m quite looking forward to seeing!

Q. M'lud, I plead reading the website during my lunch break.  In further mitigation, perhaps it was your mention of plastic and transistors in the intro to the manual that threw me, knowing I had a valve one... ;)
 
The diagram's great thanks.  Everything clicks into automatic: first thought was "replace C21, 10nF output valve grid feed"!
 
You may like to inform your readership who may wish to work from these diagrams (unless you already have and I've missed that also) that the voltage readings quoted would have been measured with an Avo 7 or 8 meter.  Measuring with a digital meter (with a far greater input resistance) will tend to report higher values than those quoted on the sheets, as they don't load the circuit you're measuring so much.
 
Thanks for the advice also on the dried lubricants.  My photographic nerdity concerns restoring/repairing old still and cine cameras and the lubricant problem is a continual bugbear - particularly, I've found, with Russian equipment and Agfa focussing helicals!
 
I'll tell you something about my experiences with your favourite Eumig P8 which may amuse, though at the time I found little to laugh about.  I found one of the Phonomatic variety some 25 years ago, with all parts still sealed in the plastic bags.  Attached a mains plug and gave it a go.  Found out the hard way the projector casing was at mains potential.  The cause of this was the mains cable: remember I unsealed the package myself.   The plug on the projector end had been wired with the earth and live reversed (perhaps the artisan in question was red/green colour-blind).  So I never liked them since - and never did work out why the took up film the 'wrong way'!

Later.  Q. Just to close this one out, a note to say many thanks for the info you supplied and posted on your website.  I’ve taken delivery of the Mark S and it’s immaculate – everything free running and undamaged with the exception of the motor pivots, of which there is no trace remaining!  I’ll be following your advice to manufacture same.

A. Nice to be appreciated.

Specto

(This is distilled from a much longer exchange).

Q.

I have a Specto 9.5mm film projector and a 16mm one; the problem I have is on the dual machine the double claw goes left

and right but has stopped going up and down. Do I need to be into the gearbox to fix this problem, if so do you know the

procedure to get into the gears.

A.

I've come across Specto's running backwards, but not your problem.

There are two cams (see pic). The one nearest the lamphouse you can't see as it's behind a retaining plate; this is the up and down

cam. The other, nearest the lens, is the to and fro. The problem may be as simple as the round cam assembly being

loose on the shaft. There are usually one or two little grub screws that hold it to the shaft. You can see the screw hole

for one of them in the pic. They may well need an Allen key rather than a screwdriver - take care to use the right size

or you may damage the heads. It needs to be in synch with the to and fro movement. It sounds unlikely in principle that

the gearbox would go at all if there was something wrong with one of the drive shafts. I assume you've kept the gearbox

oiled. If you feel you need to go into the gearbox, I assume you have viewed the Specto pix in the multi-gauge section of

my site; I don't know of any written material. Basically, you have to remove all the chain drive and sprockets from the back, and the

inching knob, to remove the cover plate.

Please make a point of telling me how you go on - I'd like to know what's wrong!

Q.

On looking closer with magnifying glass, I noticed the shaft is moving as I turn the cam manually. I put a small dot on the shaft that holds

cam, and noticed it rotating the same as the cam. I got into the gearbox and found that the gear that drives the cam was running loose on

the shaft. There is a flat on the shaft to help secure it.

Is it usual for the claw to have a tapping noise when projecting a film?

The Specto 16mm instruction book it says the gears are worked with oil only, and the dual is a mixture of grease and oil.

Could you by any chance describe a ghostly image and what causes it?

A.

Oh well, I’ve now learned something new re Specto gearboxes. (We also discovered in the course of correspondence that there are at least

two different sizes – bore and front-to-back dimension – of chain sprocket in the drive train).

Interesting about the lubrication - I can't be bothered and use oil and sometimes a bit of spray grease, which is nice and thin. In the old days,

I used Vaseline on claws/cams.

Ghosting is most easily seen on titles, and takes the form of streaks of semi-transparent stuff below or above the letters.

It is caused by the shutter being incorrectly set, presumably as a result of the stuff you've had to do with the mech. It's fairly easy to fix on a

Specto; the shutter is held onto a shaft by the usual grub screw and will turn freely once released. You then turn the machine over using the

inching knob, with the lens holder open so you can see what the claw is doing.

You need for the big blade of the shutter to be juuuust about covering the gate aperture when the claw starts the down stoke, and for it still

to be covering the aperture until the claw stops going down. (The small blade is called a flicker blade and is just to reduce flicker. It won't cover

the aperture enough to stop streaking.) That way, none of the movement of the film can be seen on screen, which is what causes the streaking.  

You need to check at the other end of the claw stroke, to make sure the aperture is still covered when the claw stops moving down. Only just

again - the shutter blocks light so to maximise light on the screen the main blade is kept as small as possible, so it has to be adjusted just right.

You may have to compromise a bit to get the best balance of covering the aperture at each end of the claw stroke. Then you just tighten up the

shutter and it should be OK. You may need to do a bit of trial and error, tho. Watch the fore and aft alignment of the shutter - you don't want it

catching the inside of the lamphouse as it turns. Really a silent projector needs three blades to avoid flicker but manufacturers were always trying

to find ways round it. Trouble is, as light output rose, any flicker became more noticeable. Nonetheless, the Specto is pretty good; I believe they

avoided problems by a fast shutter rotation rate.

You often get a clicking/tapping noise with film - it varies from film to film. Only experience will tell you if it's actually a problem - make sure the

film isn't being damaged. Best way to do this is to make up a short loop of film and let it run thru 50 times and then see if it's getting scratched or

if the sprockets are getting "picked" or strained.

Q. Another Specto question. Other than a mistimed shutter can you think of what may cause a ghosting to appear on mainly intertitles. Is this something that could be caused by the claw?

Pathé Vox

Q. As well as an active filmmaker, I am a passionate collector of movie machines and films. Although I don't have the amounts you have, I have
a fair amount of "stuff" in 35mm, 28mm, 9.5mm, 8mm and super-8mm. I have never come across 17.5,other than in editing sound, (magnetic
sound that is), for 35mm films (yes, every time I can, I edit my work on my 35mm moviola) and often times one uses 35mm full coat magnetic
film split in two, for the sake of economy.

I recently acquired a Pathé Vox and since I have been having a lot of trouble to find documentation about it, and having stumbled across
your enlightening web page, I wonder if you could clarify some doubts I have about the machine.

First: how can I tell if my machine is a Type "V" or a Type "S"? Second: how can I find a lamp for the machine? I would rather stick to the original, which I believe is a 15v 200w for the Type "S" or a 15v 400W for the type "V", but I gather from your writing that this may be difficult or impractical. Third: which leads me to finding out if the adaptation you made for a modern lamp, keeping the original projector's base, is successful and maybe available or reproducible? Fourth: my machine came without the sound module. Is there any way you think to find one? and finally, Fifth: I found on e-bay a BPY10 photo-diode. Since you mention it as useful in your web page I purchased it, but how is it used? Thank you very much for the help you may be able to provide with these issues. And thank you for your generosity in sharing your knowledge in the www.

A. Lot of questions. There are only 3/4 variants of the Vox. It was available 1st in a silent version, known as the "S". The doubt over 3/4 is because I don't know if both Vox and Super Vox were sold in this way. There are just the two sound machines, the Vox, with the 15v 200w lamp and the Super Vox with 31v 400w. If you look in the picture gallery, part 1, near the top are pictures of a Vox, complete with amplifier, an "S", and a Super Vox without amplifier. This is because I don't use the original amp at all; I put a cell such as a BPY 10 where the sound mirror originally fitted, and plug it straight into the mic input of an external amp. (You will find quite a lot about this in the Vox section). It is best to use a projector amp as they are specifically designed to cope with film sound tracks. Ditto speaker. I tend to use Bell & Howell a lot for this. Some of the principal differences are obvious from the pix. The Vox has switches side by side, the Super one above the other. The Super has an additional bearing support bracket for the lower sprocket. The Super has a bulge in the side of the base casting where the power feeds in, the Vox has this at the back of the amp. The Super Vox has a larger inching knob and a different lamphouse, partly to accommodate a larger motor. Even with a Super Vox, it is advisable to give the motor a hand when starting, and the Vox was notorious for needing this. It matters because if one were the sort of idiot who turns the motor off leaving the lamp switch on, when restarting, if the motor refuses to turn at once, you have a hole in the film. Both the original lamps are almost impossible to find and probably don't give such good results as modern ones. They also have a pretty limited life - 30-40 hours maybe.

The Vox is easy to convert as there is a 15v 150watt halogen lamp, in both "peanut" and dichroic mirror types. The dichroic is I find too difficult to
fit. My earliest conversions were by fixing a lampholder to the side of the lamphouse, with the lamp horizontal - this works for both Vox and Super. I
prefer to use a system that does not change the machine, as I have shown on the site. Unfortunately, I let my conversion go with a projector and will
have to start again, but it does make converting the Vox simple and above all non-damaging.  If you get the lamp filament into the same position as the original, it works fine.

The Super Vox is more difficult - there is no commonly-available 31v lamp to use a s a direct replacement. The transformer in mine was unwound a bit to give 24v, so as to allow the use of the 24v 150w or 200 or 250 in peanut or dichroic - with the dichroic you just have to scrape off a bit of the silvering to allow light thru for the sound track.

I have a number of Vox and Super Vox machines in various states of completeness - or not. There is a good chance I could provide any spares you
might need. And I am happy to advise on any particular problem you encounter. Note that one of the weaknesses of these machines is that the main drive
gears can wear, particularly on the Vox - the precise alignment of the motor is vital.

Enough for now. Do some more reading and get in touch again. You sound very literate and are doing interesting stuff. If you go back as far as an entry
dated 1st February in my What's new section, you will see extracts from Flickers. Either a subscriber or a writer of stuff for it is always welcome.

Q. Thanks a lot for your generosity and patience. I will research and do some more, no doubt. Anyways, my Vox seems to be working fine, mechanically, so I will work on getting a light source and adapting the BPY10 as you have done. One thing is pretty evident; the lens is quite dirty inside, so I have to figure a way to disassemble it and clean it. It's a 32 mm, identical to the one my Pathé Lux uses. Any chance that you would have a spare original sound module to sell? And thanks a lot for the FLICKERS tip!

A. The sound side of a Vox comprises the amp in the big case at the back and the sound drum/flywheel assembly. Which are you missing? And are you clear
yet which Vox you have? The lens is probably not worth bothering with. I remove the glass and bore out the inside of the lens sleeve to fit an old-style B&H lens, which are quite common and of far better quality. The same thing doesn't seem to work as well with a Lux, oddly enough. Equally oddly, I am currently working on a Lux, fitting a new motor speed resistance and converting the lamp to halogen, without harming the original machine. I have decided it's time to get in touch with my inner Lux out and will be studying it quite closely, especially the notching system. PS my other half is Membership Secretary for Flickers - please send money!

Q. I am sure I have the Vox. The box part, on the rear, is missing: does that hold both the amp and the drum/flywheel assembly? It does have the mirror and the lens device to throw light onto it. But someone in its past life removed the sound components. My Lux is OK except that the shutter is quite unsteady. If I carefully apply pressure on the gate/plate it becomes steadier (and slower) so I guess something is out of alignment in the shutter/registration pin zone. But I haven't been able to figure it out. The notching system works well nevertheless. Which brings me to asking you if you know of the existence of repair manuals/schematics for the Lux and/or the Vox.

I will definitely will be subscribing to Flickers!

A.

Q. I realize that my understanding of the Pathé Vox is not as good as I supposed: my machine does have the sound module you sent in pictures. I just don't seem to see the "D" screw in your picture anywhere, even if I take out the lamp house fully, (including the "second layer" that holds the reflector for the lamp to concentrate the light beam thru the image lens). I guess that what I'm really interested in getting (for the sake of making the machine "complete") is the "box" that comes behind the machine. I assume now, this should be the amplifier? Also the fan to cool of the lamp is lacking its back cover, which might or not be part of that "back box" of the Vox. Mine came without that too. I'm attaching a couple of pictures of my Vox unit, to make my descriptions, hopefully, more clear.

When I got my Lux, its lamp socket had already been tampered with. When the bulb it came with gave out I had to redo the socket to the best of my ability. I adapted a CEW/CFE 120v 150w which works fine. All of this to say that I can't tell if its a YA or a YC. I have taken also three snapshots of my Pathé Lux machine, showing the piece of cork (ugly I know, but the unsteadiness of the projected images otherwise exasperate me) I have devised as a temporary method to achieve more stability. Also I photographed the removable gate. It seems to me like the claws do not retract enough or are maybe a bit worn in the tip, making them too thick to do a proper job. This by comparing the claw movement in other projectors. Maybe they are made of the weak alloy you indicate? I wonder if there is a remedy for this.

A. Thank you for the pix – a picture is worth a thousand words.

 

I’m not happy with your sound lens tube (sound telescope).  It should protrude through the bottom of the lamphouse; the hole in the bottom of the lamphouse is bigger than the tube, to allow it to move as I have already described. In order to prevent light spilling down this hole and causing hum, there is a little cover that slides over the top of the tube, and moves with it. I’ll attach a pic of one.

 

Are you sure you mean screw D and not screw A? Can you send a more close-up pic of the sound telescope, please? If you do mean screw A, it may well just be a case of finding another that fits. Inside the tube there should be a slit, formed by two semi-circular plates that don’t quite meet. This can be adjusted – a narrower slit means better treble response but less volume, so it depends on how your particular set-up works – I would not touch this for now. It is accessed by unscrewing the top of the tube. I’m not sure without looking why there are two screws at D – one should control the angle of the slit, which must be absolutely square to the film.

 

I suggest you go to this page of my site www.cinerdistan.co.uk/spare_parts.htm. There are here just a few example pictures from a large number of spare part pictures. If you give me your address, I can send you a CD-ROM with them all on, and looking rather better than the examples. Both the Lux and the Vox are covered, so they could well be useful to you and in identifying between us exactly which part we are talking about. If you want to send money for a subscription to Flickers, and for the CD, I take PayPal and will walk into the next room to give your sub to the membership secretary for you. Then you could just email the form.

 

I have had this problem with the back cover missing from the Vox fan and made a new one out of aluminium sheet – there’s a pic on the website. I think I kept a template, so I could help with that. As to the amp – usually, the contents have been thrown away of replaced, so you won’t get an original lamp. Also, it does add to the weight; a Vox is 15 kilos without it. The two attached pix show separately the amp casing and the base into which it fits. Note that the terminals at the rear of the machine are not the original power input; this was at the back of the amp. The three wires are for 110v, 130v and common. You should find the 130v and 110v marked on a terminal strip inside the base so you can find out which is which. I usually eliminate the 13ov connections and use the third terminal as an earth.

 

Your Lux looks like a YA, with an all steel gate and bigger lamphouse. Without looking, it’s hard to say what your problem might be. I take it the gate springs are OK? The two leaves bed together neatly? Is the tension device that holds back the top spool working properly – ditto bottom spool? Unless it’s been damaged, the claw is unlikely to be the problem – it’s made of hardened steel. The problem with all old projectors is that they are temperamental, and can need a lot of time and attention to be made to work properly, as can be seen from my own experiences as recounted on the site.

 

Re lamps, you are aware that the Lux is basically for notched films and if you use too powerful a lamp, the film will be damaged when the machine stops for the still frame.

 

Q. I'm attaching more pictures, all CUs of the sound telescope in my machine. I screwed "A" all the way one way and then in the other way and then took out the little cover (your picture "Vox sound unit 008.jpg") and then also the "B" screws to show you that the two screws you mark as "D" (now I realize they are two and not only one) are not present in mine. The amp I guess is the part photographed in "super Vox 007a.jpg" , I believe. You say I won't find that, correct? I see a unit similar to mine with the exception of that part, the amp and the base I assume, in your site (photo gallery, second picture down on the right hand side) As for the Lux, I believe the gate and the loop holders are fine. So I will keep trying to figure that one up.

I'll be happy to get the subscription thru you and also the CD and any helping documents you may be able to send me, as the fan cover template you mention. (Maybe another template for the lamp adaptation? That would be very helpful) I know the subscription is 21 British Pounds. How about the rest?

A. I can only assume the D screws are a difference in the Super. The amp at 7a has obviously been much modified - most of those controls and sockets were simply not present in the original. And it's a Super. The empty case in the pix in my last but one email is for a Vox. If you offered me lots of money and were prepared to pay a hefty shipping charge, you could have it, I suppose. That aside, the only cost is £3 for the CD-ROM, unless you decide to buy the
amp thing, which we can discuss separately. So just send £24 PayPal and we'll start your sub with the issue published last week, and I'll put the CD in with it.
I will try to look out the template and decide how best to help - will take some time, I fear. I don't think I have a template for the lamp mod - I made
a mistake and sold the projector it was in before copying it.

Q. I managed to make the light work on my Vox, following your guidance. I just want to share a few snapshots of the unit I built, using the base of a burned out lamp that I was told by the guy I got the Vox from, was the lamp the Vox used originally. It turns out he did not give me a A1/105 but a A1/52 and I had to file it down to have it fit the Vox socket, once I broke the glass and got rid of the guts of the burnt lamp.

Also I decided to connect the EVB directly to the wires and disconnect them from the socket terminal, to avoid the chance of having a short circuit or something even worse. The first 15v 150w peanut lamp got burned. I had measured the voltage in the lamp socket 16v DC but somehow when I got the EVB lamp connected it was 19.5 AC if I connected the 110V wall input. And now the 130v input gives the lamp 16v AC!. I'm pretty sure that a few days ago both were 16v DC. Maybe I just made a silly mistake, but I seriously doubt it. In any case 16v AC works fine now. 

The projected image was very jerky. I discovered that the film gate is way too wide, and for the moment made a cardboard "T" that I placed in the feed end of the film gate, that works a makeshift "pressure plate" and makes the projected image steady. I will have to find  a more elegant way to address that problem later. Also I think, having projected a silent Laurel and Hardy, that the motor is running under 24fps. I'll also have to look into that some more.
But what puzzles me now is that the light from the sound telescope doesn't seem to hit the film. It hits the mirror but not the film.

My  BPY10 just arrived from England yesterday and seems to be working fine: the volt meter shows an increase when the photodiode is approached to a light source.

A. Hmmmmmmmm.

The Vox has a problem with wear to the sides of the gate channel - much of it is due to that silly sideways shift between top sprocket and gate, which places a lateral pressure on the film. The channel being cast in fairly soft metal does tend to wear. The ideal solution is the have the sides milled out and replacement "runners" made of steel fitted. This I have not yet tried as my engineering skills are limited. I have also seen machines with a pair of rollers above the gate to get the film into position and so avoid the lateral pressure.

 

The motor speed is determined by a) the gear at the front and b) the frequency of the mains supply. It is an induction motor and runs at a fixed speed which depends on the mains frequency. We have 60 cycles per second and the US uses 50 - or vice versa, I never can remember which way round it is. Have you got a condenser/capacitor? This is critical not just to starting but also to running at the correct speed.

 

Send me a pic of the rear of the sound telescope holder, and we'll look at it then.

 

Incidentally, you seem from the pic to have the lamp filament arranged fore and aft. This might just be the angle of the view. Anyway, the filament should be across the projector, presenting its broad face to the condenser lens.

Q. You were right about the position of the lamp. I corrected that the best I could, and tried to put it as close to the condenser lens as possible. That seemed to help also the sound telescope. But I had to open it up and I discovered that mine had the slit thru which the light passes almost closed. I had to unscrew a lens part to access four small screws that hold the two halves that make the slit and I fixed them so that the slit was as wide as possible.

The light is now barely touching the film side but in order to achieve that I had to let the sound telescope loosely attached and help pushing it towards the projector. Still it seems to me it hits it barely. But the sound telescope cant be pushed any more without modifying the aperture thru which it comes thru in the lamp housing. In other words, if the hole was wider or simply elongated towards the outside of the projector, that would allow me to have the light from the sound telescope hit the film optical sound area more centred. For the moment I think it's off axis. But I can see a brilliant point of light in the edge of the film now. I feel that is progress.

A. No no! Slit must be as narrow as possible or you will just get muffled. bass-y sound if any - I usually try to make mine even narrower than original as I'm usually either getting better light or better cell performance.

Here is a pic of the back of a Vox sound reader. You will see at "A" two horizontal raised ribs, and a vertical one at "B" - that is to say, vertical when the reader is actually in place. There should be on the body of the sound module corresponding slots. These are to enable the reader to pivot slightly to allow it to read the track and get into the best position. I have had similar problems to yours in the past. Your best approach might be to take the whole sound module out so you can see what is actually happening where the reader meets the body of the module. It may well be necessary to file some of the ribs down a bit, but be very cautious. I have known readers that could actually move in first one direction and then another as I tightened the adjusting knob - it's a very weird arrangement, but you should be able to make it function, certainly better than it is at the moment. I assume you have ensured the springs are not too tight, to give it room to move.

 

Another possibility that occurs to me is the position of the sound drum. It has needle-point bearings at each end and there is scope for some adjustment of the position of the drum, and therefore the sound-track. The basic point to remember is that the system does actually work, so if it doesn't, it's because something is wring.

 

About the lamp. Be careful not to put it too close to the lens - there is an optimum position anyway, and putting it too close may risk heat cracking the condenser lens, which tends to be visible on the screen. You can check the optimum position by running the lamp with a lower voltage so you can still see it on screen but are not blinded by the light. You can then fiddle to find which position gives the best and most even illumination.

Incidentally, I find it good practice to run a loop of leader thru the projector a few dozen times before serious use, then check to see if any scratching occurs. Prevention is better than cure.

Q. I have put the slit back to minimum as you advised. I have also looked into the sound drum. I managed to make the film (I think) shift a little bit out. But the sound telescope still only hits its side, too little I think (without having any optical sound film in hand). Looked into filing the parts you indicate, but I'm still convinced that the problem is that the sound telescope cant point inwards enough because it hits the hole in the lamp housing.

It will be great if you can help me with some test film. If you do find something suitable you can live without, please let me know how much I should send you for it and its mailing. I really appreciate a lot your kind help. I guess I will start setting my photo diode and figuring out connections etc. while I get some sound film. Any guidance on that respect, again, will be highly appreciated.

By the way, I have been assuming that the sound telescope's light should hit the edge of the film and not the mirror. In my machine the light can easily hit the mirror, but I find that illogical. Unless I'm missing something...Looking again more carefully at the sound reader and its insertion on the projector I realized that you where totally right in suggesting to file those ribs. I did a bit of filing on them and already the light beam seems to get better where it should. I decided to be cautious and not go too far yet, before testing the actual performance once I'm ready to do it. So in other words, there is still room to file some more those ribs. Also, I managed to get the actual tube very low, just millimetres away from the film, thinking that that may help to get better light onto the sound track. But putting a piece of paper underneath the beam to see where it goes and how it goes, I feel that it is maybe too diffused or out of focus. The same beam in the same piece of paper looks sharper lower down. So I'm wondering if I'm making a mistake and the tube should go  back and away from the film, in order to get a more focused light beam. Should I simply find a way to attach my BPY10 under the film so It catches the light as best as possible? I guess so. What do you think?

A. I have had another thought. There may be a bit of adjustment possible in the position of the sound module. If you were to slacken the bolts that secure it to the base, this might allow you to move it a bit and help avoid the reader hitting the side of the lamphouse. As for height of the sound telescope, I suggest you study the pictures in my section on the Vox - bound to be some pix there that would help, tho' be a bit wary in case Vox and Super Vox are different. I have always worked by looking at the light on the film - what you should have is a very thin strip, only tenths of a millimetre thick and about 1.5 to 2mm across. It should look as sharp and clean as possible; the point of focus is the film, not the mirror, tho' ideally one does fine tuning by adjusting while running a film. As for the mirror, bear in mind it has probably got a fair bit of adjustment, so the light hitting it or not may not be a very good guide. You can fit your BPY10 by removing the mirror and fitting a small bracket, as detailed on a certain website.......

I have despatched to you by air mail a (part) sound film and one of my lamp adapters for the Baby - I am making a small batch due to popular demand. You

will learn that the worst thing about 9.5 is the people who use it or, more accurately, ab-use it. I have attached a copy of a piece I did for another of our film mags, specifically for 9.5ers. The film will confirm much of what I say. You will see two bits of paper sticking out of the reel of film. Between these two, the film is junk and should be thrown away, I just left it in to show you how awful it can get. The bit taped on the front of the film is one of the worst bits. The rest is not brilliant, but should provide you with decent test footage. In the first part of the film, before I gave up, you will see examples of the kind of repair I do, as described, of course, on my website. When you see what the film is, you will understand why the idea of you playing it repeatedly there in Mexico affords me a smile of amusement (He will find it's the Trooping of the Colour)

 

Q. That is a very pleasant surprise!  THANK YOU VERY MUCH!!!

I will try this new adjustment you suggest. And it makes a lot of sense to have the light beam focused at the film. Should I simply find a way to attach my BPY10 under the film so It catches the light as best as possible? I guess so.

I'm curious about that template you have for the rear motor cover. Fortunately my 13 year old twins are not as naive as they used to be still some years/months ago, but one of them already asked me yesterday (pointing his finger to the revolving blades, but cautiously away from them blades) what that was... So its my hint to get that covered asap.

Great funny/sad text you sent me. You can imagine that I find a lot of the same in my part of the world. I'm patiently going thru a big box of assorted 9.5 400ft rolls I purchased in a local flea market with some jewels I think, to be recovered. For example, there is this 400 ft roll of a Mexican tenist group of the 1930s that seem to have had sessions not to far from my home in place (Tacubaya) that was then countryside and now has a totally urban landscape. I treated it last year with vitafilm for three months with some success, and I'm still fighting to revive it. It tends to curl inwards because of improper storage. I'm thinking about immersing it in a water bath (like the ones one would use after processing to clean up left-overs) and re-dry it in my US Army manual film dryer. Of course, I have to do some tests before with expired 16mm raw stock, before I dare to do that to my cherished piece of forgotten history. It will probably have to wait some time until I have the leisure to try that.

When I get Pathé baby spools one thing that happens a lot is that they detach from the core. I haven't been able to figure out how to properly re-attach them. The Pathé baby spools don't seem made to be disassembled, which would make sense. Any ideas on that issue ?I got the B&H projector lens I found on e-bay to replace the original one in my Vox. The difference is indeed amazing. Its a Super Proval 2 inch 1.6f and had to do some filing on it to get it to the lens housing far in enough to get focus. But once I managed to do it, the projected image was great.  I'll have to work on the lens sleeve to make it a more permanent job. Its getting there.
 

A. I apologise for being so stupid. I was fixated on the idea of a template I thought I had. It has taken me all of 10 minutes to remove the back from a Vox, trace round the cover, make a cardboard template, take a few photos and write this. Some days, my brain hurts. I will send the card one by post next week. Note that the screws do not go thru the cover; the heads of the screws hold it in place.

The Baby cassettes are designed to not let the end of the film come out. Each film has a slot joining 3 perforations at the end; this is far enough from the end to ensure that the film stops (nothing for the claw to work on) before there is any pull on the film.

The film is secured to the core of the cassette by spring clips. The one I am looking at has a spring clip inside the cassette, round the core, with a gap so the film can get thru the slit in the core. I am not sure what this is supposed to do - it's very difficult to do anything with it - I assume it was extra fixing added during manufacture.

In addition, there is a similar spring clip inside the core, but outside the cassette. You can see this in the attached picture, as I have removed it - it's easily pushed out from the side with the slot in the spindle for the rewind. Now, it's a very long time since I fiddled with a Baby cassette, but memory says you feed the film thru the slot in the core into the centre and the put the spring clip in so it traps the end of the film. It may be possible, too, to twist the clip inside the cassette around a bit so it helps to trap the film.

Pathé used to sell a little two-ended device; one end cut the notches in the side of the film, the other cut the slot down the middle of the film to ensure the film stopped in time to avoid pulling it out of the cassette. (You will see three examples in the second pic down on the left on the website page on Gear, which is accessed from the main 9.5 page.) Perhaps you have this vital slot missing on some of your films, or are using a different projector which pulls the end before it reaches the slot?

As you can no doubt see, the construction of the cassettes is such that taking them apart would be hard and putting them back together properly almost impossible.

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Debrie

Q. As you dissected a André Debrie 16mm-projector I hope you can answer a question which has kept me busy since someone told me: "I don't know if it is a good idea that you bought that old projector from a woman who had never used it. Oil has certainly clotted in the thin pipes of the oiling system." And indeed it seems it has. How can I change the oil? In spite of the fact  this pre-war model of a projector looks awfully solid I am a little afraid to break something crucial. I hope you can to help me.

A. Please bear in mind that my only experience is with the grey D16 model.
I would be very surprised to find that oil has solidified as you suggest. Do you have any particular evidence for this?
What I did find was that  thin oil will not work in this machine. The oil is circulated by a fairly basic mechanical pump and it needs quite thick oil - car engine oil sort of thing - to function. I assume you know about the oil flow adjuster at the top.
You will have seen the drain plug at the bottom of the lower oil reservoir. You can drain the oil quite simply through here. If there is a serious problem of clogging, you may be able to use a specialist car product designed to flush an engine. This may be preferable to dismantling, but I wouldn't worry too much about taking the machine to bits - it was
specifically designed on a modular basis so complete assemblies could be easily replaced. You could try mixing  thick oil with something like WD40 to flush the system through, but if it's too thin, it won't go round. I think the whole front section will come off if you remove the screws on the perimeter of the round section - just take the usual care not to lose
anything. You will need to do this if you decide to open up the lower oil reservoir - one of the two screws holding it on is only accessible if you remove the front section. Please think carefully before doing this - there are oil seals top and bottom of the reservoir which you would have to make watertight (and oil-tight) again. Also, if you are afraid of breaking
anything, the glass of the reservoir is one of the most breakable parts. Best left alone. You can remove the oil tube running from top to bottom quite simply just by undoing the two nuts - these again form oil-tight joints, but should I think go back OK as I think they rely on compression rather than seals. I think the first thing to do is drain whatever oil is in there and try some thick oil. However, if it is really true that oil was never added, there may be mechanical damage. This machine is designed to run with a constant flow of oil and if this wasn't done, either from lack of oil or failure to adjust to
keep the flow going,  it could ultimately seize up.
 

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Q. I have a question about the Pathé Baby motor. I recently acquired one from Buckingham films, and it works fine on the 115 v 60Hz here in the USA. But I am somewhat concerned about it's safety as the internal wiring looks pretty bad and the connections to the mains terminals look pretty dangerous. I am considering taking it apart and attempting a rewiring job. Would you advise this or not, and how difficult a job is it? Any pitfalls to watch out for, or any recommendations?

Lamp Conversion

Q. I am trying to fit a 12v 100w dichroic mirror lamp to a Bolex (maybe 24v 200w would be better). I have made an adjustable bracket using a lampholder from an Elf 16mm machine. How do I position the lamp to get the best light? What are the criteria?

A. There is only one criterion - what it looks like on the screen. There are specific focal distances for such lamps (some are quoted in Lamp Data), but these are more use to manufacturers of projectors than to the amateur. The distance is apparently measured from the back of the mirror rather than from the filament for one thing, which makes it more difficult, but anyway, it does not address the issues of lateral and vertical location, which are just as important. There are variations in focal length, there are primary and secondary foci, there are differences relating to the size of the gate aperture you are trying to illuminate (unhelpful if you are attempting to deal with a multi-gauge machine, especially if 8mm is involved. The tri-gauge Bolex G3 had a special lens to deal with the offset of the 8mm aperture, but the lighting has obviously to be a compromise when there is a 3- or 4-fold difference in aperture).

So at the end of the day there is no practical alternative to good old trial and error. The way to do this while keeping both your fingers and your sight is to feed a reduced voltage thru to the lamp - 6v should be ample for a 12v lamp, and you could probably manage with it for the 24v lamp too. (Don't go thinking "Ah yes, halve the voltage", because you will literally get your fingers burned if you try that with the higher voltage lamp.) This should give you a level of light sufficient to gauge the best lamp position, using a small screen a few feet from the lens, with a reduced level of heat that should help with handling. It's still a fiddly job, but is much eased by an adjustable holder such as you have - once you get the position approximately right, you can fine tune. You may have noticed that with some projectors the lamp glows when the projector is on. This is supposed to warm it, prevent thermal shock and prolong lamp life as compared with going from cold to full power. This question of lamp life seems to have exercised amateurs quite a bit in days gone by, judging by old copies of Home Movies and Home Talkies, for example. This uses just a couple of volts at most; what you need is just a brighter version.

Don't expect to get a perfectly even illumination - you need to go for the best compromise between evenness and brightness. Once you apply full power, and with a film in the gate, it will be impossible to detect any unevenness. One final point - disengaging the still frame mech to avoid accidental operation might be a good idea.

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Pathé KOK

Q. Do any operating instructions exist for the Pathé KOK 28mm projector? if not, can you tell me, what the small knurled disc on the main body just in front of the gate, with what looks like a ball bearing in the centre is for? I assume the hole (with cover plate) just under the lens is a oil hole?

A. Mais naturellement il y a un manuel! Vous le trouverez sous 28mm, nommé Instructions. Malheureusement, le manuel est en Français, ce qui pourrait poser quelques problèmes pour ceux d'entre nous qui ne peuvent pas hacker le Froggo. En plus, le manuel ne traite pas des trous dans votre question, mais il serait étonnant si tous les deux ne soient pas pour l'huile.

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Emulsion in or out?

Q. Which way round does the film go thru the projector? Which way does emulsion face? Which side of the spool does the film feed from?

A. This is all the fault of Pathé, who made their silent films, up to the time sound was introduced, unspool from the back of the reel (ie nearest the projector). No other film does this as far as I know. It may be because of the gauge's origins in 30ft notched cassettes. The emulsion had to be on the inside to protect from rubbing on the metal cassette, and the design required a feed from what would become the back of the reel.

The important thing is not the position of the emulsion (unless perhaps you are loading film chargers?) but whether the film appears OK on the screen, with titles the right way round, right side up, from the start rather then the end and preferably with the sound track on the correct side. If all of these are right, who cares about the emulsion? It does matter, of course, because projectors are designed to minimise any rubbing. The emulsion is on the inside of sprockets, away from retaining rollers, and rollers that take the film round corners do it with the emulsion on the outside wherever possible. With 9.5, there is the unique factor of potential claw scratching in the picture area. It makes sense, therefore, for the emulsion to face away from the claw. We have all seen the damage a Baby claw can do. It may well have been this that ultimately made Pathé change (the Vox, H, 200B, Lux et al all have the claw in front of the film). I seem to recall some reference in the amateur cine press or maybe Pathescope Monthly on the reasons for the decision - anyone got chapter and verse?

So, basically, except for most 9.5 silent, feed from the front of the spool (or underside as I sometimes think of it), and never mind the emulsion so long as the film is right on the screen. Sometimes this means a twist in the take-up belt to get it to rotate the right way. It's not the end of the world if a film takes up the "wrong" way, tho' it can mean it winds floopy and could mean problems if the film is near the normal maximum capacity of the take-up spool.

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8mm Gauge terminology

Q. What is the difference between Regular 8, Super 8 etc?

A. Regular 8, Normal 8 and Standard 8 are all terms for the first 8mm gauge. This was created by doubling the number of perforations in 16mm film, and having four images in the space previously occupied by one 16mm image. The film was produced 16mm wide, and run through the camera twice, (hence "double-run" 8mm) then split after developing. The advantage was much greater economy both in film used and in developing. Kodak introduced the gauge in America in 1932, and shortly thereafter it came to Europe. Eventually, magnetic sound was added and experiments were made with optical sound; one or two projectors were made able to run this, but remained curiosities as there were no films to buy.

This was because Kodak introduced Super 8. This was widely suspected of being a marketing ploy to get enthusiasts to buy all their equipment all over again. However, whatever the truth in that suspicion, there were sound technical reasons for the change. The Standard 8mm image was tiny and, although capable of producing excellent results, was a highly inefficient use of the film area because of the (relatively) giant 16mm sprocket holes. Adding sound just made things worse - tiny tracks straining to produce acceptable results, or yet further loss of image area. Super 8 had very small sprocket holes (too small some said, concerned about how long films would last) and an image that was both wider and taller, even with a sound track (magnetic for the most part, but optical particularly for use in aircraft entertainment systems). A magnetic sound track adds thickness to the film on one side, so a "balance" track, squeezed between the sprockets and the edge of the film, was added, which was exploited to give stereo sound.

At about the same time, Fuji introduced Single 8. In terms of format (film size etc.), this was identical to Super 8. The difference lay in the film cartridge, which was much more on the lines of Pathé's 9.5mm chargers than the squarer Super 8 cartridge, with feed and take-up one above the other rather than side by side as in the Kodak cartridges. The other difference was that Fuji used polyester-based film, stronger than acetate so it could be made thinner. This helped with the amount of film that could be got into their cartridge (9.5 never managed even 30ft) to match Kodak's 50ft cartridge. The only disadvantage with polyester (if you think it is a disadvantage), is that it can't be spliced with normal cement and so for practical purposes could only be spliced with tape. Polyester commercial prints can be found, looking suspiciously short on the reel for their claimed length.

The row about the introduction of Super 8 to confuse the existing multi-gauge scene was huge and rumbled on for years. Some of the sting was removed by the introduction of Dual-Gauge projectors for both Standard 8 and Super 8. Some machines even claimed to be triple gauge, citing Single 8 which was, of course identical to Super 8 (barring some projector problems arising from the thinner film base).

One problem that could not be, or at least was not, overcome, was projectors able to show Super 8 as well as 9.5 or 16. Standard 8 had a 16mm background and, by coincidence, the pitch of 9.5 and 16 was almost exactly the same. This meant (genuinely) tri-gauge projectors could be made (see Multi-Gauge).

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Notched Films

Q. What are notched films?

A. When Pathé first introduced 9.5mm, the maximum length of film in a film charger and in a cassette for the projector was 10 metres or 30ft. This presumably reflected the rather limited thinking about what was a very new venture. Later, 60ft cassettes were added, then Super Attachments taking up to 300ft. In order to get the maximum run time out of such a short length, Pathé decided to use still frames for titles, and often for the start of scenes or for static shots. The Baby projector had an ingenious device for allowing this. A notch in the film allowed a small cam to move, setting in train the withdrawal of the claw and a mechanism that automatically re-engaged the claw after a fixed number of turns of the crank handle. (The earliest Babies had a very long "dwell" time; this was later reduced as being too boring). This enabled the short cassettes to last for as much as three or four minutes, as opposed to little more than a minute if run without pause. This was all part of a total design concept; with all this stopping and starting, it was too complicated to have sprockets, and of course a low power lamp was essential to avoid frying the film. This in turn meant relatively low illumination levels, positively dark by modern standards but apparently more acceptable in those days of innocence.

The notches in the film obviously showed on the screen, so the film actually stopped a frame later to give a proper picture. An important additional feature was the provision of a slot near the end of the film, replacing the perforations. The claw could not operate, so the film stopped before it was shredded or ripped out of the cassette; the end of films was securely fixed to the tiny core in the cassette. An interesting sidelight is that the front ends of films were specially heat-treated to impart a curl to ensure smooth feed through onto the take-up in the base of the machine. Pathé actually patented this idea. Many printed films also had a very shallow but very sharp oblong notch in the opposite side to the main notch; I've never known why. (I asked an expert, the legendary Patrick Moules. He said that when triple prints were notched, before being slit, the notch was either slightly over-size or out of position, so that the outer part of the notch cut into the adjacent strip. This only happened, of course, with two of the three strips.) Notching devices were sold so that 9.5 film users could put the correct notches and slots in their own films. One other thing; many notched prints came from a period when the image quality was superb, which is why they are so prized by collectors.

The problem was that, as time went by, demand grew for higher levels of illumination. This meant more powerful lamps, that emitted more heat. Huge numbers of notched films now bear witness to the disastrous consequences; ignoring all admonitions to use the correct, low power lamp for notched films, users blithely disregarded the consequences, used the higher -power lamps and fried the titles. These then shrank and buckled or even burned right thru; splicing the damage out was a very limited option since there were so few frames of title to start with. Opening titles seem to suffer the worst and are often completely absent. At one time, Pathé sold sets of running titles that users could splice into their boughten films, either to repair damage or for use on high-power projectors or ones that couldn't do notches anyway. Given Pathé's penchant for using lots of titles to disguise cuts made in editing, this can't have been very popular.

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Light Output

Q. Why do low voltage lamps give more light than mains lamps?

Getting a bit technical here. As I understand it, lower voltage lamps can have their filaments more closely spaced, giving more intense light in a smaller area, highly suitable for narrow-gauge films (is it something to do with how far filaments must be apart at different voltages to prevent short-circuiting or arcing?). Another factor at play is that, for sound machines like the Vox, Debrie and GB L516 that used the lamp to read the sound-track, rather than a separate exciter lamp (which tend to be low volts/high amps - see the end of the table in lampdata.wdb), the lower the voltage the better. Lower voltage means less hum from the AC supply, I am told. Quite how this applies to 110 volt machines like the Debrie and GB L516 I don't know; maybe they deal with the problem in the amplifier.

Quartz Halogen, Quartz Iodine (QI), Tungsten Halogen etc. are all terms for a technology quite different from the straightforward incandescent lamp. They can be smaller, with smaller filaments, yet give brighter and whiter light, especially when combined with a built-in dichroic mirror, which removes the need for a condenser lens - a significant advantage for old projector nerds trying to uprate old projectors.   So, for instance, the standard 24v 250 watt lamp with integral dichroic mirror gives a better light than a 1000 watt or even a 1200 watt incandescent. QI lamps need to reach a certain temperature to operate properly; I am told they also dislike direct cooling and can go black if direct cooling is applied, but they produce much less heat than the equivalent incandescent. They quite rapidly became the standard for narrow-gauge use, relegating the incandescent lamp to history. The peanut-type QI lamps can pretty much directly replace old lamps, tho' some experimentation with exact mounting position might help. Basically, I feel that if the filament is in the right place, then fair dinkum. Dichrioc mirror lamps have a specific focal distance; examples are in the lamp table referred to above. I think there may be more to be said on this subject; input would be welcome.

Then, of course, there are even higher power lamps. There was a version of the B&H 620/630 series with a carbon arc, the B&H 609. I've never felt brave enough to consider carbon arcs; complicated. Then there was the Marc lamp, which B&H in particular tended to use. They were some form of discharge lamp, and took a while to reach full operating output and colour temperature. They also needed complicated boxes of electronics, and used high-voltage circuitry. This last bit is also true of Xenon lamps, and some early machines had large separate boxes of stuff. Then came switched mode power supplies (I can say it but I don't understand it) which allowed much smaller boxes of gubbins and could therefore be fitted inside the projector. Most Xenon machines were 16mm pedestal models, which had lots of room for boxes of electronics, but there were some semi-portables like the Elf 2000 series. B&H also did them, but I've never seen one. I'm accused of being a light freak because I have Xenon's wherever I can 8, 9.5 (a Buckingham conversion) 16 and 35.

Beyond even Xenon in terms of potential for narrow-gauge users is the sort of lamp being fitted to digital video projectors. Bill Parsons converted a GS 1200 to one of these lamps, and a direct comparison with Xenon was arranged at a film convention; no question, the new lamp was brighter than the GS 1200 Xenon.

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