H Page 2
PATHESCOPE "H" Page 2
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.
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Been playing with Pathescope H machines again. I have, just for fun, replaced the motor speed resistance on one with an ordinary house light dimmer control, which, with only a little modification, fits neatly. Pic one shows the various parts involved; pic 2 shows why I felt able to break my rule of not irreversibly altering a machine.
In pic 1, directly below the mounting plate for the resistance, is the insulated bush, which was riveted in place, and through which the speed control knob is mounted. Left is the knob, which originally had an integral shaft on which the "wiper" contact for the resistance was mounted. Both this and the bush I removed, forcibly, tho' actually it would be possible to put them back, I suppose. Above is the dimmer control. When fitting the knob to the dimmer shaft, I had to bear in mind a) that the rotary travel of the dimmer is far greater than that for the resistance, so has to be mounted far enough out to avoid hitting the studs that restricted the travel of the knob when using the resistance and b) that this particular dimmer incorporates a push-on push-off switch. This would mean it was possible to have the projector lamp on with the motor off, never a good idea. I just had to use spacers to ensure the push mech could not operate. The knob had to be drilled out to fit the dimmer shaft, and I drilled and tapped for a grub screw to hold it in place.
The last item in the pic is a shutter assembly, but this is shown enlarged from 2 views in pic 2. This is why I felt I could "sacrifice" a projector. The assembly is pretty flimsy altogether, but the basic problem is that the fibre gear gets worn and eventually loses enough teeth to stop working. I have three units like this, all now useless. I think the problem is that the shutter rotates very fast - I suppose because it's got only 2 blades and should have 3 to avoid flicker at silent speed. The fibre gear has a semi-helical cut, because it engages at 90 degrees with a (very) helical gear inside the machine.. A 90 degree drive like this must, I am sure, place additional strain on the gears involved. The fibre gear cannot easily be removed, as its shaft is sort of riveted in place, so it would be even more expensive to have re-engineered than the Bolex gear. With all the other faults the H has, and without the special capabilities of the Bolex (to show notched films with a decent size picture and using a sprocket), I fear the game is not worth the candle, so the H will soon become a display-only machine.
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I am tr
ying 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. And the shutter is in the wrong place, after the film rather than between the lamp and the film, to reduce heat on the film.
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.
Here are the arm and various other H bits repainted. It's very long. (I gave it a quick try and found it was easily big enuff for a 2000' reel or more - guess I overdid it a bit.)
Also some pix of my current H restoration project (Nov 2013). I've been trying to improve a bit on my past efforts; the lampholder is a bit neater now, with a rim included to locate it in the original lamphole. To get filament height right, I've trimmed a bit off the leg pins of the 12v 100w lamp. There is up and down adjustment for the lampholder using the original lamp securing screw, tho' I had to put a bit of rod into the hole first, as the securing screw originally just had to reach the T piece on the rear of the lamp.
I've also tried a different way of fixing the rear rubber feet. The square blocks are held in place by a screw that goes down that larger hole in each one, right thru the inserts to which the motor end brackets are fixed. In the top view, you can see one of these brackets in place, with a classy domed nut over the end of the screw to secure the bracket, which I thort looked better than an ordinary nut. The other screw can be seen still. Going back to the underside, the square blocks are level with the "inside" of the base cover (far left in pic 1 above) and the rear feet are secured to the blocks, not the cover, with a screw into the second, smaller hole. The reason for all this malarkey is that the base cover is only secured by screws directly into the bakelite (see pic 3) and do not have the brass inserts used elsewhere. These holes just do not have the strength to hold anything much, so the weight of the machine has to go direct to the (rear) feet and not via the base cover. I've used a different low-voltage lighting transformer I had lying around, which lent itself very neatly to re-using the original holes that supported the 80v 100w lamp transformer. The switch is a centre-off as described for my earlier effort..
While we are talking of the base of the machine, I have been experimenting with ways of cleaning and polishing the bakelite. It's difficult; there seems to be some sort of "bloom" beneath the surface. So far, T-Cut and some stuff called Black Bright, designed for re-blackening black plastic car bumpers, seem reasonable. Anyone any other ideas?
As you know, I am pretty anti making permanent changes to projectors. Your mission, should you choose to accept it, is to identify the two changes that I have felt obliged to make.
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Here's the rest of the story in pix. In pic 1, which is the direct follow-on to pic 4 in the row above, the (replaced) wires that go thru the back of the motor can be seen. They have to end up tucked away behind the brush housings, where they will hopefully stay and not leap out and foul the commutator. There are three "through" wires, two for the lamp and 1 for the motor, to the speed control. There is a fourth wire that enters at each hole in the motor casing, connecting the motor field winding to the speed control and the mains respectively. The wires from the motor windings had also perished and could not be replaced completely, so I used liquid rubber insulation to coat them. It's quite fiddly to get the wires thru, without leaving too much slack at the projector end (the other end can be trimmed when you get there). Then you have to start building the lamphouse on top of the motor and trimming and connecting the various wires. (You should already have fitted the lamp socket and connected its wires to the terminals on the underside of the assembly, to which you now add the two thru wires from the motor. You didn't? Go back 3 spaces!).
Setting the motor in position is important. There is plenty of adjustment in the two end brackets and by using the big fibre washers that are used as spacers between the motor and the brackets. Sadly, as I discovered only after a first, failed, attempt, this doesn't really matter. What does matter is the mech which, as you can just see in pic 4 of the previous row, showing the base on its own, sits in a groove and had no slack for lateral adjustment, just a bit of fore and aft. So you have to match the motor unit to the mech to align the gate and the gate lock/release mechanism correctly. Then you set up the motor brackets to match. I found a particular problem in that the fixing screw (upper front side) for fixing the motor bracket was continually getting in the way and scraping the motor housing. In the end, I just cut the slot of the screw deeper and filed the head down - the head for some reason is quite deep, so there was plenty of scope for this.
Pic 2 shows the underside wiring as finished. I have maybe gone a bit overboard on the earth connections - there are three in practice - but I worry about a bakelite machine with metal bits that mite not always be linked to each other. Pix 3&4 are really to show you the repaints, which comprise those shown previously plus the mech side plate at the rear. Note the lamphouse is more of a matt finish - I used Barbecue paint to withstand the heat from the lamp - it is usually paint damage from the lamp that allows rust to creep into so many lamphouses. I discovered that the positioning of the mech side plate is critical to the free running of the mech - despite all those screws and some locating pins, there is a small amount of play that is enough to cause all those bearings to bind if it's positioned wrongly. I just slackened the screws a bit, ran the motor slowly and levered/bashed the plate about to get the free-est running.
Pic 5 is the finished article and 6 shows the new feet in place.
With all these changes, the H is a very competent little projector. It only has 300' arms (the lower arm has a cross-bracing rod half-way down, not something I've noticed before), but it has an excellent gate and claw. My quibble with it is that, because the drive train is mainly geared, it does tend to make an unusual sound, a sort of grinding from the gears (altho' the also-geared 200B don't seem to). But I chickened out of removing the pulleys and the side plate (again) to see if some Molybdenum grease would help. Maybe later.