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Old 15th May 2019, 9:07 pm   #1
af024
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Default Bell and Howell TQII 1652 16mm projector

Bell and Howell TQII 1652 16mm ‘Filmosound’ Projector woes

Well I suppose it was bound to happen at some point. I recently acquired some more 16mm films and thought I’d dig out the projector, which had been resting, probably for 3-4 years in the back of a cupboard.

I didn’t give it a thought and just applied mains, switched on, pressed the auto feed level and offered up a nicely trimmed film with its leader in great anticipation. Well it only ran the film in probably half way, went very noisy then suddenly stopped (seized) with the motor thrashing away on a stalled belt. Well you can all probably guess what the cause was, yes a split worm gear.

I knew what I was in for – not only in tracking down a suitable new replacement but also in stripping the machine down to fit it.

I luckily came across a fantastic solid white nylon new high spec replacement, complete with an unusually nice larger diameter collar into which two grub-type screws are used to clamp it to the axle. Far better than anything else I’ve seen and exactly the correct dimensions/pitch etc. I promptly ordered one, and whilst I was waiting for it to arrive, I started the strip down.

It was far worse than a video on You Tube suggested. The TQII 1652 seemed to have much more to have to remove e.g:-

• Lens
• All lamps
• Transformer
• Motor
• Sound drum flywheel
• Sound head assy
• Numerous gears
• Top internal bracket
• Shutter bracket
• Shuttle arms
• In-out bracket
• Shutter assy
• Belt
• Pulley
• Worm gear axle bearings
• A cam on the worm gear axle

Of course it’s also really important to mark-up how the sprockets are synched with the shuttle/claw and how the gears mesh with the worm (assuming that they still retain the correct timing following the seizure of course.

For good measure, I even measured up exactly where things were, horizontally on the axle, I’d also put a line around the sound head assy prior to its removal (since that’s mounted through slots and its position need to be reinstated later).

/cont
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Old 15th May 2019, 9:08 pm   #2
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Default Re: Bell and Howell TQII 1652 16mm projector

Anyhow, a day later (I kid you not!), all was ready to accommodate the new worm which actually arrived the very next day (impressive!).

By the way, the old worm just wouldn’t let go of the axle. With all grub screws removed, I twisted, shoved, pulled, pushed, squirted WD40, all sorts. It was an absolute pain to get it off and my hands are still aching even now!

So I carefully positioned the new worm, special cam etc and started the careful re-build.
I was doing fantastically well, quite proud of myself actually, but somewhere along the way, when I was trying to free off some seized sound drum clamp arms (which I also noticed at some point), the stupid photocell fell out of the sound assy and must have got wedged under one of the projector’s feet. Needless to say that the black plastic surround got damaged. I ended up drilling two tiny holes through the side of the bit of plastic that broke off and the main body of it in an attempt to stitch it back together with pins and glue. It actually worked ok and probably would have been fine, but I’m a bit fussy, so I went on the hunt for a NOS replacement. To my amazement I actually found one, so that was also placed on order. It too arrived the following day (amazing). The next problem was to try and work out how it was mounted. This wasn’t easy as it relies upon being wedged in down the side of the sound drum with a metal wedge and grub screw affair. What’s worse, you can’t actually get to it without removing the optical lens from the sound drum assy (which I must reposition and focus up later).

I suspect that the photocell was already on the move way before I started the job as I seem to remember that the last time I used the projector, the sound seemed rather muffled. So another problem found and fixed (hopefully).

OK, it was all back together and time for a test. First of all, I undertook a manual (laborious) lace-up to see if all the timing looked ok - it was thank goodness. I didn’t fancy another strip down or attempt to twist any offending sprocket relative to its gear to correct anything. I guess it’s lesson to would be other brave people though – always worth a check before it all goes back into the projector!

So time for switch on.

Well we have another problem now. The motor is running like the clappers (technical term). It’s trying to shift film at circa 40-50 fps instead of 24! The 18/24 speed switch does nothing – it remains flat out.

What’s more, the shuttle arms make one heck of a racket. I think that’s a combination of the crazy speed and perhaps some bad adjustment (except I’ve not messed with them – they are where they are and everything went back where it should be). The manual isn’t very helpful on how I might adjust these arms (special tools etc), but it does say to resist adjusting them to ‘minimise noise’. I’m hoping that some kind soul on here might be able to give me some tips about this. It looks like 1 x grub screw.

So that’s something to remember to attend to later once the speed issue is resolved.
Well this is a bit of a mystery. Was it a case of excessive speed seeing an already compromised worm gear off, or was it a case of the worm gear failure, followed by mech seizure and excessive motor current being drawn that damaged the speed servo? Not sure.
The servos took a bit of finding actually, it’s tucked behind the motor, low down and looks like a small potted box. It’s states EXM030 on it. This doesn’t agree with the manual (which states EXC030 or perhaps EXO030?). Mine also has some additional diodes present which are not shown in the manual. Not sure what’s going on there, but it does look like a factory fit.

So I’m guessing at this point that all of my efforts have come to nothing as this part is no doubt unobtainable from anywhere. I can’t even open it up to see what might be duff inside. It’s clearly a servo as there is feedback from the motor – see the circuit extract. I suppose a substitute (redesign) might be possible, but that’s tough going to obtain a reinstatement of switchable 18/24 fps, especially when I don’t know the nature of the feedback etc. There’s also the racket from the shuttle arms (which actually look like they are about to fall out of the mount, they are that loose!).

So guys, any ideas please?

I’m really disappointed and depressed about this, as this particular projector has some sentimental value attached to it. So near, yet so far. Is this how these servos typically failed back in the day?

Regards,

Andy

Photos

• P1010427.jpg -wide view of projector insides
• P1010428.jpg - close-up of cracked worm gear
• P1010445.jpg - shuttle arms and removed shutter
• P1010447.jpg - gear meshing
• P1010451.jpg - seized film/sound drum tensioner arms (and photocell/PCB assy)
• P1010456.jpg - servo module
• P1010459.jpg - servo location (plus diodes)
• P1010460.jpg - grub screw adjuster – shuttle arms (shown at the top)
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Old 15th May 2019, 9:10 pm   #3
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Default Re: Bell and Howell TQII 1652 16mm projector

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Old 15th May 2019, 9:11 pm   #4
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Default Re: Bell and Howell TQII 1652 16mm projector

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Old 16th May 2019, 9:15 pm   #5
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Default Re: Bell and Howell TQII 1652 16mm projector

I forgot to show the servo circuit. The dc supply comes in on the left hand side - pins 1 and 4.
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Old 17th May 2019, 9:37 pm   #6
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Default Re: Bell and Howell TQII 1652 16mm projector

Hi!

Try not to laugh too much, but have you tried boiling the servo module in fast–boiling water for about 20 minutes in a pan of water?

Quite a number of epoxy fillings have a "Glass Transition Temperature" of about 70–80°C, so if you boil the module for about 20 min, that will be above the G.T.T., after which you might find the filling material has softened somewhat, enabling you to try digging it out with a screwdriver, etc., if you're careful – it's worth a try, but I'd make sure you can source a spare unit just in case!

Chris Williams
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Old 17th May 2019, 9:58 pm   #7
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Default Re: Bell and Howell TQII 1652 16mm projector

Hello Chris,

No I didn't laugh, really, I didn't, but I have to say that I hadn't thought about boiling it . Thank you for the tip. I may well have a go at that, assuming that I can satisfy myself that it is indeed the servo that's packed in and not the loss of feedback pulses (or volts), or whatever it gets from the motor.

As for tracking a spare down .. well so far, that's proving to be very tough indeed.

Regards,

Andy
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Old 18th May 2019, 5:22 am   #8
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Default Re: Bell and Howell TQII 1652 16mm projector

Normally these things use the freqeuency of the signal from the motor's tachogenerator as feedback. It's a more reliable indication of the speed than the voltage from said generator.

Looking at the circuit, the tachogenerator seems to be the 2 yellow wires from the motor. With the unit off and at least one of those wires disconnected, you should get some DC resistance between them due to the tachogenerator windings. Not shorted, but not open either.

With the motor running, a 'scope should show an AC voltage (sinusoidal-ish?) between those 2 wires.

Alas the B&H projector I have is an older one with an AC induction motor so I can't be more help.
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Old 18th May 2019, 8:53 am   #9
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Default Re: Bell and Howell TQII 1652 16mm projector

Thank you Tony,

I'll have a prod around and report back.

The servo package is really small - I'm quite amazed by that given the size of the motor.

I'll have to do some jumpering about with some croc leads or something, but I'll do that and report back. I'm not sure whether the tacho will need some exciting from the servo module however. I'll see what happens with it disconnected.

Regards,

Andy
PS Funny how it looks like the older machines will live longer eh! Well done you for having the AC type. Does that use gears for the two speeds then Tony?
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Old 18th May 2019, 10:30 am   #10
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Default Re: Bell and Howell TQII 1652 16mm projector

Try Kevin Browne aka KB Cine Repairs in Nottingham, who might be able to source you a module or suggest an alternative.

Failing finding an original, there are generic frequency-to-voltage converters that can be adjusted to suit a range of magnetic tonewheel tachos, to provide feedback to a standard DC motor driver module. This is expensive but just shown as an example:
https://uk.rs-online.com/web/p/emi-f...ories/0440509/
There are doubtless direct-from-China equivalents cheap enough to take the fun out of building your own.
See also these people, IIRC we've had some controllers from them and they seem quite flexible and open-sourcey:
https://www.4qd.co.uk/product-category/controllers/

The induction-motor projectors use stepped pulleys on the motor and main shafts, with a striker operated by a lever above the film track. Hence the warning printed there only to change speed with the projector running. The earlier machines with universal motors switched electrically between two centrifugal governors.

Coincidentally, I also had problems with a projector speed control yesterday - a Lenze inverter that drives the 3-phase motor in a Philips DP75. Proj kept on running but lots of smoke came out. Rifa suppression caps, naturally. Grr.
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Old 18th May 2019, 10:59 am   #11
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Default Re: Bell and Howell TQII 1652 16mm projector

Can't help with the speed control beyond what the others have said.

I changed the worm on my 8D644 probably 20 years ago. Massive job not to be undertaken lightly, I suspect no-one at B&H ever thought it would need changing. I didn't want to repeat the experience so directed a friend to have his identical machine done by a repairer (not the one listed above). When the machine came back I wondered how they'd dealt with a particularly hard to access bolt I'd struggled with. The answer was simple - they hadn't refitted it!

My machine has the AC motor and ran fine for many years, but has lately started to suffer from wow and my attempts to trace this have failed so far.
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Old 18th May 2019, 1:21 pm   #12
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Default Re: Bell and Howell TQII 1652 16mm projector

Quote:
Originally Posted by af024 View Post
Thank you Tony,

I'll have a prod around and report back.

The servo package is really small - I'm quite amazed by that given the size of the motor.

I'll have to do some jumpering about with some croc leads or something, but I'll do that and report back. I'm not sure whether the tacho will need some exciting from the servo module however. I'll see what happens with it disconnected.

Regards,

Andy
PS Funny how it looks like the older machines will live longer eh! Well done you for having the AC type. Does that use gears for the two speeds then Tony?
Normally the tachogenerator is a spinning magnet and a wound stator (often a single flat coil with pole pieces that appear as 'teeth' round the hole in the middle). They will thus give an output without any excitation from the control module. In fact spinning the motor fairly fast by hand should give some signal on a 'scope.

It's been some time since I've had the covers off my projector (Filosound 655Q) but the service manual indicates that the speed change is a belt that's mechanically shifted between 2 pulleys on the motor shaft.

As for your last comment, I often find the older something is, the easier it is to repair and thus the longer I can keep it going. It's a lot easier to find spares for a 1970's PDP11 than for a 5 year old PC in my experience.
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Old 18th May 2019, 4:14 pm   #13
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Default Re: Bell and Howell TQII 1652 16mm projector

You may find suitable spares from these people. (They also make the worm gear!)

http://www.classichomecinema.co.uk/

Look under their section for film equipment.
I have no connection with the company, but a friend I know who used to change the worm gears suggested trying them when I was chatting with him on the phone today and I mentioned your Bell and Howell.

John
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Old 18th May 2019, 4:50 pm   #14
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Default Re: Bell and Howell TQII 1652 16mm projector

Thank you for all of your great comments, links and suggestions. I am encouraged.

Just now I've managed to grab a few moments to drag the 'scope and a multimeter out to see what's what.

Here are the results:-

Motor supply blue/red = 5 ohm
Tacho grey/grey (shown drawing as yellow/yellow on circuit rather strangely) = 408 ohm
Motor supply volts = 38.4 Vd.c.

Scope trace settings (sorry about the bad photo):-
5V/div, 0 Vd.c. on centreline, 0.2ms/div
So I make that circa 29V pk-pk off the tacho, and 1351 Hz (motor running flat out off the 38.4 Vd.c. supply)
The above measurement were taken with the tacho not connected to servo and the motor supply taken from the faulty servo output (38.4 Vd.c.)

There is no difference when the servo tacho circuit is disconnected.

The two diodes that I mentioned seem ok, although I only tested them as standard diodes, not zeners.

I also came across this interesting service bulletin (about the servo and diodes). I'm guessing that they were expecting trouble way back then for some reason!

Regards,

Andy
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Old 18th May 2019, 5:38 pm   #15
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Default Re: Bell and Howell TQII 1652 16mm projector

It looks like the tach pick-up is OK. As the motor gets faster, not only does the frequency increase, but the peak-peak voltage will rise proportionately.

With a DC motor, it's probably a transistor circuit in the box, and a common failure mode of power transistors is short-circuit, leaving your motor at full speed ahead.

Whatever is in the little box can be replicated once its nature is found out. It could be working on either the frequency or the amplitude of the tach signal, though the amplitude version would be concidered rather crude... but stranger things are found.

David
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Old 18th May 2019, 8:20 pm   #16
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Default Re: Bell and Howell TQII 1652 16mm projector

Did you check the rest of the speed control circuit? There are two pots that set the speeds and a switch possibly for play and wind/rewind?
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Old 19th May 2019, 5:00 pm   #17
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Default Re: Bell and Howell TQII 1652 16mm projector

Thank you for you further comments.

I suspect that you are correct David - a shorted transistor. It's an amazingly small module. Goodness knows what's in it.

As for the reference circuit, well I think it's ok. At least I'm getting a change on voltage at pin 5 when I switch from 18 fps to 24 fps - not much though - only 0.4 Vd.c. This might be ok?

For completeness:-

U1/EXC-030/XU1 d.c. voltages (projector running, everything connected as it should be):-

Pin Volts
1 39.2
2 15.3
3 0.7
4 0
5 10.8 at 18 fps, 10.4 at 24 fps
6 9
7 9

Regards,

Andy
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Old 22nd May 2019, 9:48 pm   #18
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Default Re: Bell and Howell TQII 1652 16mm projector

I've just messaged someone who is currently selling a TQII for spares. I thought it would be my chance to obtain a replacement servo, but alas, when I asked if he might be able to check if the speed switch actually changed the speed of the motor, the answer that came back was, 'No it doesn't, it's just stuck on one speed and runs fast'.

So it seems that this isn't an isolated incident.

I tried contacting classic home cinema and regrettably they don't stock much B&H stuff, so that fast became a dead end.

I bet there are more failures out there ...
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Old 23rd May 2019, 7:55 am   #19
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Default Re: Bell and Howell TQII 1652 16mm projector

It sounds like you don't so much need a replacement servo module as an improved servo module, designed to not blow up.

Anything driving a DC motor will see an inductive load and nasty transients from brush-commutator interruptions and sparking. Without good protection, this will degrade semiconductors leading to eventual failure.

Projector motors take a fair bit of power, and that module looks small. So either it uses the metal it's mounted to as a heatsink, or else the output stage is switch-mode.

The first thing is you need an AC tachogenerator to voltage converter. Have a look at LM2907/LM2917. They're as old as the hills (I used a pair for electronic rev counter and speedo when I rebuilt my old Cooper S in 1979!)

There's an opamp in the chip which will make your loop amplifier... all you need then is a good beefy power stage - well larded with transient protection!

David
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Old 23rd May 2019, 9:28 am   #20
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Default Re: Bell and Howell TQII 1652 16mm projector

I have spoken again to the person I know who used to change B&H worm gears.
Apparently the model you have is not regarded as a good one. He says that the servo units did not normally give trouble but the motors are suspect in that model.
He is contacting someone else who may have spares, I will post if he has any luck.

John
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