Pathescope "H"

 

PATHESCOPE "H" Page 1

 

 

Page 2 

 

Couple of points I discovered when trying to fettle an H (Aug 2012).

 

H 002     h motor_resb     H speed_fan_008

 

Pic 1 shows (bottom centre) the two wires with round spring fittings at the end, which connect the motor winding to the brushes. NB in this pic the spring fittings are not actually in place around the brush mountings. Anyway, I had a motor in which one of these spring fittings was oversize and floopy, I let it pass as it was still making contact with the brush mounting. Wrong! I then had some weird problems with the motor not running right - too slow, sometimes running even tho' I had switched off - and the part of the resistance actually in use with a current in it - ie between the wiper and the upper of the two connections, rapidly glowed red hot and started to ping off whatever was left of that stuff they cover the wire with. I then tried without the resistance, and within two minutes the field winding burned out with much smoke. I finally came to the view that these problems must be due to that floopy spring shorting to the motor casing. I was lucky and had a spare coil, but be warned, especially since, as I have explained elsewhere (see below), it is terribly easy to stretch these springs if you don't disconnect them before removing the field coil from the motor housing.

 

The second pic illustrates the electrical connection to the resistance wiper. The little insulated block bottom centre of pic 3 is riveted to the curved section of the lamphouse structure seen in pic 2. The speed control knob passes thru this insulated block, then thru a metal strip shaped as per the right-hand bit of pic 2, then the wiper fits above this and is held in place by a grub screw which locks the bits together. The metal connector strip is bent over at one end to fit the scalloped edge of the insulated block. This stops the strip from moving and causing a short-circuit. These metal strips are a bit flimsy and break easily. The one on this machine had lost most of the bent-over portion but, not at that time realising the importance of this, I thought it would do. Wrong! Nice flash and the trip on the mains cut out. I then had to cut and shape a new strip. The shape needs to be just so because the first thing the strip can touch if it moves is one of the rivets that hold it in place, which are very close by. This is what caused my short.

 

Anyway, I hope my misadventures will help you avoid such pitfalls.

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Back end of 2011, I had email correspondence with George Speller, who had 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.

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Pathe H_with_Soundhead     Pathe H_Soundhead     H sound

Mikael Barnard has 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. 

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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. (I have had one H where this route had ben bypassed with wires going direct from the base to the lamphouse.) 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. 

 

H lamp_conv_006     H lamp_conv_003     H lamp_conv_002     H lamp_conv_008

 

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 in the bakelite 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.

H 006

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; below is the intact version of the motor casting that broke.

 

 H 004     H 007     H 001     H 002     H 005

 

The next four above 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 (see above). 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 the pattern shown below. 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. 

 

H 012     H dichroic_conv_002     H dichroic_conv_003


While we are on the subject of lamps, I thought I would add some pix of an ambitious attempt at fitting a dichroic mirror lamp - it's not mine or, if it was, it was a copy of one I had seen. It's a very tight fit, especially round the motor resistance. On the other hand, I am coming very much to the view that these lamps, especially if the projection lens can be uprated, give much better results than "peanut" bulbs limited by elderly optics.

 

 H 010     H underside     H 015     H stripped_002     h stripped_001a     H mech1a     H 018     H 019     H 020     

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 Speller's pix; link near the 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 5 is the other side also stripped down, just for balance. Pic 6 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. 7 & 8 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. The 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.

Pic 9 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. 

 

pathescope-h pathescope-h pathescope-h pathescope-h pathescope-h

pathescope-h pathescope-h pathescope-h

 

 

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