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PATHESCOPE "H"

 

 

 

Back end of 2011, I had email correspondence with George Speller, who has been working on a Pathescope "H".

It is of a type that I have not previously encountered, with a large resistance mat in the base rather than a tranny -

presumably for universal application on DC as well as AC? Anyway, George has done a lot of work stripping it down

and building it back up, and has now sent a link to a series of photos (that's the way to do it!) of the process. You

can see his pix at www.mid-summer-night.co.uk.

 

 

           

 

Mikael Barnard has been busy. He found me some old ebay pix of a Pathescope "H" with an add-on sound unit, a

thing of which I was not previously aware. After he first mentioned it, I did find a passing reference in an advert.

Been fiddling with an H, a machine I don't think I've ever run a film on, the principal reason being the unavailability of lamps.

It is an odd machine; the wires to the lamp, and the wire via the speed control resistance to the motor, all pass through the motor

casing and close to the motor shaft and commutator. Then the space to wire up the lamp and resistance is very tight and inaccessible.

 I had to go there as the insulation of the wire to the resistance had rotted, leaving a bare wire to short all over the place.

It was a bugger of a job. You have to dismantle the motor and remove the field winding, taking care not to stretch the springs

that form the connection to the brushes and which have to be slipped free before you pull the windings out. Oh well, at least I know now.

 

                 

 

Here is a prototype lamp conversion. It uses a lampholder which says on the packet it's for an A1/259, but it seems to accept a 12v 100w. The lampholder has some tiny holes in, which take a 12BA bolt. I drilled and tapped a couple of holes for these. Then the wires have to pass out thru holes drilled below the mirror, or you can't get the base to the right position, and thru again to connect underneath. It should now be possible to fit the original lamp wires over the lampholder wires. As you know, I'm not keen on permanent changes to projectors, but even tho' I've made some new holes, there is nothing here to prevent reverting to the original lamp. Actually, looking from a different angle for these pix, I think I shall have to raise the lampholder a bit to get the filament central. My current idea is to use a low-voltage lighting tranny - they are quite small - and either fit it round the original tranny and just bypass it, or if necessary, remove it altogether but NOT throw it away, and label it up for re-use.

It's now some time later and I've been getting into H's again, as I still have a number. Found one that looked to be in very good nick, but the lamphouse would not tilt back. The dreaded Mazac disease had struck. I just could not get one end of the motor out of its support. In the end, I had to break it. Right is the motor support bracket with part of the motor casing still stuck in it. Even then, it took a lot to shift it. I decided to cannibalise another machine; this is the intact version of the motor casting that broke.

 

                      

 

These show the motor field winding. You have to remove this in order to get at the wires for both motor and lamp, which run through the motor in the area round the brushes. The motor wires in particular tend to rot, not desirable considering their location. The connections from the winding to the brushes are via wires with sprung loops on the end. WARNING - before you remove the field winding you MUST push these off the brush terminals, or you will stretch and damage them and have all sorts of trouble correcting what you have done. Trust me on this one - I did it. You can see I have not yet reconnected them, in case I need to go in again. The final pic shows another danger - the fan is Mazac and the blades snap like  they were made of chocolate. In fact, the entire motor casting was so far gone I could break it between my fingers with no more force that it would take to break very thin chocolate.

 As you feed the winding back into the casting, four wires have to go through each of two holes in the casting (see pic just above). The length of these is critical, as the space for connections in the lamphouse area is very tight. I think this whole arrangement is crackers. I can see the point to some extent, in that this minimises any risk to the wires from bending as the motor/lamphouse assembly tilts, but running wires THROUGH the motor? Anyway, I have now re-built the motor (I had an armature with a complete fan) and tested it. Incidentally, one of the machines I have been working on has thin rubber between the motor brackets and the base. I have not come across this before, but it seems a good idea as I have found some H's very noisy.

 I next turned my attention to the lamp. I was not really happy with the one shown above, as it used a base that meant the lamp was  a bit of a force fit  - not ideal. I started out down the same line, but then changed to this pattern. I used the small (10 BA) tapped holes I had already made, but you could go larger, of course. I just used a thin bit of alu that was lying on my bench; it was more hole than metal when I'd finished. I needed spacers to get the lamp filament to the right height. The wires just go straight thru the lamp socket to the terminals beneath. A later approach is below.

 

                                         

 

Some constructional detail. The two different undersides are odd - both have the transformer with various inputs for different mains voltages, but in the first one, these have been blanked off and replaced with the resistance, labelled with the same voltages. I think I may not have understood - maybe it's something to do with different models for different voltages. Was there an "H" that didn't use the 80v 100w lamp? See also George Spellers pix; link at top of this page.

Next is a shot of the gear train, with the rear mech plate removed. The small silver gear, lower right, drives further gearing for the shutter - these are behind the empty-looking space. Since I originally wrote this, I have added a pic with labels and a further stripped down view. The latter shows the entire gear train except the lower sprocket drive which, as you can see from the previous pix, is just like the top one (I only had one loose one to demonstrate with). Pic five shows the considerable gearing-up of the shutter and the all-gear drive to the sprockets. Incidentally, to remove the plate that covers the mech you have to remove the arms (watch out for those felt washers between the arm and the sides of the frame) and the base securing bolts as well as the obvious securing screws. Six and seven are an attempt to show the peculiar constriction of the lamphouse. The front, fixed gate is attached to the main mechanism assembly; in these two shots, the plate carrying the rear gate and the condenser is in place. The lampholder is fixed to this plate, but the plate/lampholder assembly is not (at this stage) fixed in any way to the motor castings. The wires to the lamp come up thru the motor and under the motor resistance, with very little slack or "play" available. whole lot gets pulled together by the outer lamphouse. This attaches to the lugs on the rear gate plate, but also to the motor casting - I suppose it's a bit like monocoque construction, as it's certainly rigid enough when all is in place, but it's very fiddly with lots of very small screws.

The final pic shows the Eumig P8 transformer I have shoe-horned into the base, to allow use of a 12v lamp up to 100w. I have also fitted a separate lamp switch - I know the "douser" thingy obviates the need for this when starting, but you can't easily release it at the end of a film. It looks a tiny switch, mounted in the hole for the voltage pointer, slightly enlarged, but as it's only switching 230v at 100w, it don't need to be big. You can also see towards the rear of the base a hex pillar with a green earth wire and, lower down, a round brass pillar. These are to take the rear rubber feet I have fitted - the base cover plate is held by screws that just go into the bakelite. The threads are therefore very fragile and not up to taking the extra strain. The mounting bolts for the rear feet go straight to these pillars thru holes in the base plate. The pillars themselves are mounted on two of the bolts that hold down the quadrants that support each end of the motor. I have replaced these with longer bolts onto which the pillars are screwed. The front feet are simply screwed direct into the original height adjusters. The idea of all of this is to help reduce the noise and vibration you get when bakelite and metal are in direct contact with the projector stand. A bit parsimonious, even for Pathescope, not to fit rubber feet. I also removed the mains lead, fitted a very short one, with an earth, which has a standard euro fitting at the end - any standard lead will simply plug into it.

Anyway, I was sailing along happily and reached the test film stage. But before I managed to get an entire "M" reel thru, the machine started getting slower and slower and eventually the motor could not turn the mech and the belt simply slipped. I looked at the claw, and replaced it with another, but nothing I could do seemed to fix the problem. I was just about to try an alternative mech assembly, when I noticed that the inside surface of the main pulley/flywheel was scored where it touched the outside of the bearing in the mech side plate. I skimmed a tiny bit off and this seemed to work. My theory is that the pulley is in fact a bit Mazac-like and has distorted slightly and so gets jammed.

Along the way, I had a major diversion into trying to fit a slightly better lens. The problem is, the rear of the lens needs to be very close to the gate, and in the extreme may even foul the shutter. The "H" lens barrel gets very small towards the back, so does not readily lend itself to boring out and fitting a new lens within the original. I may have to make an entire new barrel.

Can I offer a couple of other words of caution. The nut holding the main pulley on its shaft has a left hand thread. So does the nut holding the claw on,

and I think the bolt holding the claw cam may also be a cuddywuffer. On initial test, my latest H restoration showed the shutter was well out of line,

with lots of "rain" on the screen. I thought fixing this would require stripping the side off the machine again, but it turns out to be a lot simpler.

The shutter mech is a separate sub-assembly; loosening two securing nuts just above the claw allows the shutter to be pushed up and disengaged

from the rest of the mech so it can be adjusted.

 

Never having used one much, I find threading the "H" a bit strange, so thought I would reproduce the instructions.

 

                           

           

 

This was a photocopy; I've now had a chance to scan an original so hopefully there will be an improved version.

 

Have been working on another "H"; it's a very fiddly machine to work on - the wires for the lamp pass through the end of the motor, past the brushes, as does a wire to the motor resistance. I know this helps with pivoting, but the result is an extremely cramped layout where the wires meet the resistance mat and the bottom of the lamphouse. The lamphouse itself is a right hodge-podge, and all the screws need to be in place before the thing takes on any rigidity. And you have to work with the fact that there is very little "play" with all those connecting wires so you have to more or less build it in situ. I found that the motor fan was juuuust catching the casing intermittently, but to get at it to re-adjust the spacers meant virtually dismantling the lamphouse over again. And on test, the shutter has obviously gotten out of synch with all this messing around.

 

I am trying a new, simpler approach to "H" lamp conversion, using one of those mini-transformers used for modern low-voltage lighting, and a different lampholder, seen left. As you can see, it's just a standard round ceramic holder, rather crudely glued/ filler-ed into a bit of tube the size of the original lamp socket. This tube happens to be threaded, but that's not necessary. The wires just pass down thru the lamp socket to the terminals, to which the wires from the tranny also attach. The standard lamp securing screw is not quite long enough to grip without the added "T" piece, so I just stuck a little bit of thin brass rod into the hole and fitted the screw thing on top. You may be able to see that it is possible to offset the ceramic holder a bit in fixing it into the tube. This helps to bring the lamp filament closer to the original position, which is slightly forward of the centre line of the lamp socket. The tube allows up-and-down adjustment (bit trial and error unless you use a low voltage feed so you adjust the lamp while it's on - not very nice at full power, I would imagine), which may be particularly helpful. This is because there are a lot of cheap low-voltage lamps around now, and I suspect that are not up to the standard of a proper A1 Class projection lamp. Some I've seen have the filament much lower than it should be.

This particular "H" is one I've had for years, but there was a break in the motor resistance mat and I had shied away from fiddling. Being now older and bolder, I had a go, and found it was fiddly but reasonably easy to unwind a single turn of the wire, and tie the ends back together on the back face of the mat with a normal Granny knot. It's impossible to get things tight like this and, left loose, the whole thing can start to unravel. So what I've done is to use some Milliput to stick the joins down and take up any slack. This keeps the wire reasonably in line and, on results so far, seems to work well. There are at least two joins in this one, yet there seems to be no gap in the smooth change of speed as the pointer is moved.

Something else that's a problem with the "H", especially if you're converting the lamp, is the motor fan. This is a rather crude affair of 4 vanes, made of a single Mazac casting and very fragile - it's very easy to bust one off. Last one I did, I managed to bust off the two that were left, but I luckily had a little fan that would fit instead. I am looking into the possibility of making a sort of copy, with aluminium vanes glued (Gorilla glue) to a core.

 

I think lamp conversion is essential for the "H", quite apart from the difficulty of obtaining originals. 80v 100w is plain silly, and was clearly chosen for price rather than performance, and because it was, in fact, the old "S" lamp coming round again, not even the more powerful "SS" of 80v 160w. I have, as recorded above, shoe-horned a Eumig P8 tranny into an "H", but why bother when you can use a "switch mode" tranny about one fifth the size? (see left). The only problem is that at the 100w level, they can start to get a bit expensive, particularly if you pay High Street prices. Try www.cpc.co.uk  or some other big online mob. You can also see left that I have replaced the switch with a double-pole, double-throw, centre-off type. This has enabled me to wire up so that moving the switch one way turns on just the motor, and moving it quickly across the "Off" position to the other side, both motor and lamp are on, with virtually no sign that you have in fact crossed an off position on the way. This seems a good alternative to finding some way of adding another switch, as I did once before (see above). There must be switches that do off-on-on, but I've never found one. I do like to be able to run the motor without the lamp for cooling, and it may well be that the new lamp produces more heat, making this more important. The "H" does have that sliding shutter device, but you still have motor and lamp together.

I fixed the mains lead in place with a rubber band so you can see all of it. I hate those long trailing mains leads that you can't disconnect, so this is my answer to avoid cutting holes in projectors - the trailing lead has a socket into which fits a standard euro mains plug like what you get with your kettle etc. You may feel the wiring looks a bit untidy - two reasons; a) I originally wanted to take one of the mains leads to the motor from a socket on the tranny, but it flatly refused to accept the wire and b) for reasons outlined above, I wanted to leave some slack to assist future access.

I can't recall if I mentioned that initial testing showed the shutter was well out of line, with lots of "rain" on the screen. I thought fixing this would require stripping the back off the machine again, but it turns out to be a lot simpler. The shutter mech is a separate sub-assembly; loosening two securing nuts just above the claw allows the shutter to be pushed up and disengaged from the rest of the mech so it can be adjusted.

My hope is that all these changes, plus adding some rubber feet (and did you know there are/can be/ should be thin rubber pads between the motor supports/pivots and the base?), will bring the "H" up to something like I always thought it should be. With a superb claw and an excellent gate, it really should be a very good machine. Many I've seen have a grinding sort of noise from the motor or mech and don't sound the thing at all. I've sprayed a good wodge of silicone grease into the mech and ensured well-oiled bearings for the motor, and this one at least now sounds like any typical silent projector. The other big issue is, of course, those silly 300ft arms. Already I am plotting how best to extend them. I do actually have one "H" awaiting restoration which .

appears to have original 900ft arms. I may also have to look at improving the take-up, which relies solely on slippage of the wire belt, there being no slipping clutch arrangement. Here is my first attempt at a top arm; I was able to find some aluminium channel of almost exactly the same outside size as the H arm. I then cut away the thickness of the arm sides and top from the channel, so I hope to get a seamless-looking join once it has had a coat of paint. It's probably a bit long - haven't actually checked yet.

 

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