Bell and Howell TQII 1655 worm drive replacement

[PaulR]

I acquired this projector from work when we moved from showing 16mm training films to high tech video tape. Unfortunately I didn't rescue the training films one of which was an H&S one which involved someone walking through a glass panelled door with gory results and someone who looked very like the one who had just walked through the glass door setting an office on fire by substituting a paper clip for the fuse in the plug of an electric typewriter,

I bought some films for it and got rather bored of them (pre internet days) so it found its way into the loft.

Many years later (a few weeks ago) I got it out to find that the worm gear drive had split as seems to be the case with most of these machines. Initially I was put off by stories of how difficult it is to get the worm gear out and I almost took it to the tip. However I found that a 3D printed version of the worm drive was available and I decided to have a go. I have repaired three train chiming clocks and I reckoned this wouldn't be more difficult than that.

There are a couple of videos about this on youtube so I watched them several times. These involved the slightly simpler projector that does not have a still mode but they gave a good description of the disassembly procedure.

I started by taking loads of photos of the projector before I started on it (nobody ever complained about having taken too many photos) and I started the disassembly. This wasn't too difficult and I only lost one circlip as I was taking the gear trains apart. I took photos of everything as I took it apart.

Eventually I got the assembly which holds the shutter and frame advance mechanisms out. I marked the positions of all the wheels at several points by putting sticky labels of the wheels and on the surrounds and drawing lines across them. This is vital as the wheels need to be correctly meshed with the worm gear or they will tear the sprocket holes.

I found more circlips on the shaft holding the worm drive (these are not on the version with no still mode) and took them apart without taking photos. This made putting it back together more difficult but I assembled it out of the chassis to work out how it went together and found that, like a clock, there was only one way it would go back together.

Fortunately the timing of the shutter etc is fixed by tabs as it is reassembled so that wasn't a problem.

I put it back together - as so many manuals helpfully say "reassembly procedure is the reverse of the disassembly procedure" - using the photos I had taken as a guide and was amazed to find that it worked. It ran slightly slow and I adjusted the potentiometer speed control to speed it up slightly.

It wasn't anything like as difficult as I expected and not really dirty. Whoever assembled it in the first place must have been sparing with the grease. Unlike Garrard grease that used was still sufficiently grease-like for me not to go to great lengths to clean it off and replace it. I used a little silicone grease on the new worm gear and a few drops of oil here and there.

I would say, if you have a B&H projector with a split worm drive have a go at replacing it. It is not as involved as , say, an autochanger to do

[Techman]

Well done on successfully replacing the worm drive

I've got one of these and it's also developed the classic worm drive deterioration and locking up of the mechanism from its time in the loft (when I checked it several years ago), so it went back into storage again for another time another day!

Seeing as I've got a much earlier model from the early 1940s that works perfectly and doesn't suffer from any of these problems of the later ones, I was considering not bothering with it and eventually scrapping it, but I haven't made a definite decision on it yet - we'll have to see!

[vidjoman]

I did one a few years ago and it was full of grease. Very messy but it did work properly on the rebuild. I got an original part from the US. It has the stop motion so was a little more difficult but works well.

[Bobdger]

I am still trying to get one of the erospace ali worms made. I now have 3 Tq3 projectors all with cracked worms. Mine have still and frame by frame projection as well as remote change over for feature films. Bob.

[Bobdger]

Tech man, have you found a source for the 1000w 230v lamps?. I have an older 652 in the loft. Bob

[vidjoman]

What's the lamp number ? I've got a few buried in my workshop and may have one.

[PaulR]

The van-eck replacement wasn't a perfect fit. I had to increase the diameter of the bearing slightly to get it to fit the shaft. I also found that the length of the bearing was slightly short which meant that I put in a further washer to make it run reliably. I tested it using an electric drill. The still frame works but is rather noisy. I am not sure whether that is an error in my fitting of it or a slight discrepancy in its dimensions.

However, it has made the projector usable and I am very glad that it was available. An aluminium version would be ideal doesn't seem to be available at the moment

[Techman]

Originally Posted by Bobdger

Tech man, have you found a source for the 1000w 230v lamps?. I have an older 652 in the loft. Bob

No, as I've never really used it. It is actually a 652 the same as yours (actually an 8D 652, I think). The lamp in it was still working and I can't remember if there were any spares that came with it inside the speaker cabinet without checking it in the loft. I understood that the lamp was a new replacement that had had very little use in the projector. Just thinking about it, there probably weren't any spare lamps, as I remember them mentioning having to send off for the lamp that was already in it. When I first got it there was no speaker cabinet or mains lead with it as they were still in its previous owners loft and he couldn't get to them at the time. He did eventually find them and passed them on to me, although the mains lead with its special moulded on plug was quite rotten, but usable with care. The unit is complete and in good condition, still with its slip over soft cover, so seems a shame to break it up for scrap. The thing is that I've got the much older 156 model, which works fine, other than it's a little low on audio due to an issue with the optics, probably the silvering on the tiny mirror. The sound level is acceptable in a normal room and if I want more output I just hang a mic over the front of the speaker cabinet and mic it up through another (PA) amplifier, crude but effective. The internal amplifier itself has bags of gain!

[wd40addict]

The 1000W 240V lamp is either the A1/207 (glass) or A1/242 (quartz). The latter should be brighter and longer lasting.

I changed the worm on my 8D644 many years ago, this has the still picture clutch I would still say it's a fairly tricky job.

The main problem I have with it at the moment is film unspooling from the feed spool. There doesn't seem to be enough back tension and I can't work out why.

[Bobdger]

The manual says Forward take up with a 400ft spool loaded with 15ft film should produce a torque of 57 grams. and 57 - 227 grams with a 800ft full spool. taken from adjustments section of TQIII Manual 2307881. Bob

[vidjoman]

Can't remember which projectors use this but it might apply to yours. The back tension is produced by a fabric belt that the spool hub presses against and the pressure is self regulating in that with a full spool it presses hard and an almost empty spool just a lighter touch.