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Old 14th Jun 2019, 8:21 pm   #61
Lucien Nunes
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Default Re: Bell and Howell TQII 1652 16mm projector

I can't tell now whether that is 9V shown at pin 6 of the original frame wiring dwg and as per your measurement, or 0V which seems more sensible and in agreement with the new module.

Anyway, I've done a hasty redraw of the new module. As PJL says there must be a missing connection on your schematic from the regulator to the part of the rail shown connected to the opamp, which I have added.

THERE MAY BE ERRORS (either yours or mine) as I have not checked it and am now out of time to do so. Please compare back with the board itself..
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Old 15th Jun 2019, 11:10 am   #62
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Default Re: Bell and Howell TQII 1652 16mm projector

It's amazing how many different formats/presentations of film came about - thank you for sharing those comments.

Wow Lucien Nunes, not only may you have determined the nature of the failure of the MKI unit (I'll bell the terminals out and see), but you have also spent some considerable time drawing out the circuit for me! Simply fantastic. Thank you! I will do my best to go through the PCB tracks and compare things against your much better presentation.

I can confirm that I missed off a connection and yes is was power to pin 7. A good shout! For completeness I have doctored my sketch (just for the record) and attached it to this thread again.

Exciting stuff this ...

Regards,

Andy
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Old 15th Jun 2019, 11:25 am   #63
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Default Re: Bell and Howell TQII 1652 16mm projector

Andy I'm curious as to whether the voltage shown on the general wiring dwg for pin 6 is 0V or 9V. It's hard to tell on the posted image, maybe you can see it more clearly on your copy. My manual doesn't give the voltages. It looks like a 9 and you measured 9V, but evidently with the new module it's at 0V. Maybe the two are interchangeable nevertheless.

Perhaps the potted module used an alternative input stage for the tach coil with bias from pin 6, although it if it's only driving a pulse generator for frequency-to-voltage conversion I can't see much point. The low end-end voltage it puts across the speed pot seems odd though.

I'm working overseas at the moment so can't help by way of digging out a working projector and checking voltages / waveforms.
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Old 15th Jun 2019, 11:57 am   #64
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Default Re: Bell and Howell TQII 1652 16mm projector

Hello Lucien,

It looks like a '9' on the sheet, but the original resolution isn't great. Funny you were enquiring about this pin 6/pin 4 business, because I was just trying to trace things though again against your fantastic drawings (nothing untoward spotted thus far).

Something is just slightly clipped left of frame on drawing (3) on the ground line however. Would that be pin 4 perhaps?

Looking at the PCB, the bulk of the copper track ends up going to pin 4 with just a thin track joining pin 6 to the main bulk of it.

Is Z1 some kind of varister perhaps?

Interesting. Still not sure how it works though.

Regards and grateful thanks,

Andy
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Old 15th Jun 2019, 12:06 pm   #65
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Default Re: Bell and Howell TQII 1652 16mm projector

As regards the original module, pins 4 and 6 aren't solidly linked (or if they were supposed to be, they aren't now). There is a resistance reading in one direction though (interesting in itself).
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Old 15th Jun 2019, 2:14 pm   #66
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Default Re: Bell and Howell TQII 1652 16mm projector

Quote:
Would that be pin 4 perhaps?
Yes

Quote:
Is Z1 some kind of varister perhaps
Yes, that's my assumption too

Quote:
Still not sure how it works though.
Square tach pulse from Q2 triggers monostable Q3/4 to produce one identical rectangular pulse per tach coil cycle, ie. duty cycle depends on speed, smoothed by LPF to give actual speed value. U1 compares this to target speed, output flips back and forth increasing mean drive period of Q5 when speed is too low etc. U1 switching and loop constants set by RC's in feedback path.
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Old 15th Jun 2019, 3:51 pm   #67
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Default Re: Bell and Howell TQII 1652 16mm projector

Thank you Lucien,

I had to double check the position of D2, but sure enough it's there. If the tacho itself produces something of the order of 30V peak to peak, it seems really weird to short one cycle out. Mind you, I don't really know what that component is for sure. There's just an ordinary diode symbol in the PCB screen printing a that location.
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Old 15th Jun 2019, 3:54 pm   #68
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Default Re: Bell and Howell TQII 1652 16mm projector

That's the open-circuit voltage. The source impedance will be high so it's really a current source that delivers a few mA alternately into D2 and Q2, the voltage never rising above 0.7V on either half-cycle.
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Old 15th Jun 2019, 4:48 pm   #69
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Default Re: Bell and Howell TQII 1652 16mm projector

Thank you Lucien, understood.

Also, I've been trying to determine exactly what Z12 is. It's probably a TNR9G820k (although the '9' is missing off the lettering on my example). That makes it a general purposes metal oxide varistor (9mm diameter) - 50Vac rms, 65Vdc, 0.2W, 10A, 10% device according to the web.
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Old 26th Jun 2019, 10:06 pm   #70
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Default Re: Bell and Howell TQII 1652 16mm projector

Hopefully this weekend I'll have some more time to devote to this, but in the meantime, why are the pre-selected speeds 24 fps and 18 fps. I thought it was 24 fps and 16 fps. So where has 18 fps come from?
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Old 26th Jun 2019, 10:26 pm   #71
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Default Re: Bell and Howell TQII 1652 16mm projector

A badly printed 6?
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Old 27th Jun 2019, 8:38 am   #72
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Default Re: Bell and Howell TQII 1652 16mm projector

Silent speeds of 16 & 18fps were both used, 18 being a later introduction and this is a relatively late projector. In the same way, standard-8 was 16, but super-8 was usually 18fps.
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Old 27th Jun 2019, 10:05 am   #73
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Default Re: Bell and Howell TQII 1652 16mm projector

16 or 18fps aided the amateur home movie maker with less consumption of film
and battery ( or in many cases in those days) /clock spring running time.
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Old 27th Jun 2019, 3:53 pm   #74
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Default Re: Bell and Howell TQII 1652 16mm projector

I thought that the 16 - 18 frames thing was something to do with the internal fan running at motor speed and not quite being able to cool or lift the fire shutter fully at 16, so the 18 frame speed made it just able to cope with just slight speeding up of a silent film. However, that could just be hearsay!

That 'tape' method of splicing looks quite good on the face of it, but I've had several failures of old splices done this way. The most recent one was on a new (to me) film just this week where first a join in the lead in just fell apart. Then, not far into the film another one caused a problem with the film jumping the sprockets killing the loop. The photo below shows the damage and I admit that as the actual tape is still in place that it could possibly have been that whoever made that splice didn't fully remove all of the original damage to the sprocket holes. To do the job properly I had to cut out about a foot of film, and once again the good old Superglue came to the rescue with the splicer and hot air gun for a perfect repair. All my superglue repairs are so far holding out well.
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Old 27th Jun 2019, 4:15 pm   #75
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Default Re: Bell and Howell TQII 1652 16mm projector

A columnist in "Amateur Cine World" in the 1960's gave that as the reason for the introduction of 18, and berated other manufacturers for following suit. All the pre-war 8mm and 16mm amateur cameras I have come across used 16 as the standard speed.
B&H projectors could be supplied to special order with a 3 blade shutter for showing silent films, so as to give the same 48 flicks per second as sound films running at 24fps with the 2 blade shutter normally fitted to sound projectors.

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Old 27th Jun 2019, 9:13 pm   #76
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Default Re: Bell and Howell TQII 1652 16mm projector

Interesting! Thank you for your thoughts.
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Old 2nd Jul 2019, 11:09 pm   #77
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Default Re: Bell and Howell TQII 1652 16mm projector

Quote:
B&H projectors could be supplied to special order with a 3 blade shutter for showing silent films,
A few 16mm machines, the Siemens 2000 certainly, possibly a Hortson model, had adjustable shutters. A dial within the inching knob of the Siemens rotates parts of the blades relative to the mainshaft. That projector also has infinitely variable speed, so you can adjust both the flicker and jerkiness to your own preference.

If you'll permit me a digression for the purposes of comparison, the projectors I am working with here in Estonia, have two different electronic methods of speed control. The Philips DP75 70mm mech has a 3-phase motor driven by a digital inverter, therefore theoretically programmable to any speed (although the sound follower, being digital, expects SMPTE timecode at a recognised frame rate). The Sondor Nova 35mm has a microcontroller-driven movement with separate stepper motors for all sprockets including the intermittent, also the shutter, allowing it to project forward and reverse up to 60fps and fast wind to 200fps without unlacing. Its timebase only generates certain integer frame rates so it is not infintely variable like the DP75. The significant difference compared to the OP's DC motor is that no actual tacho feedback is needed in either case since the drives are synchronous. The steppers are salient i.e. they have preferred positions that they take up with each cycle, while the 3-phase motor is hysteresis-synchronous - it runs up as an induction motor and when the slip is small enough, the magnetic poles in the rotor stop moving relative to the iron and it rotates with the flux vector (which, to be fair, the inverter does watch via the main windings).

How many other speed control / change methods have been used? Centrifugal governors, resistances, gearboxes (Dad's Victor sound-on-disc machine has two gearchange knobs, one for the film and one for the record), disc and idler, belt and stepped pulley... the B&H PWM seems rather sensible compared to some of them.
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Old 20th Aug 2019, 3:27 pm   #78
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Default Re: Bell and Howell TQII 1652 16mm projector

OK, so before I fit the new speed module and feed through my tester film to set the speeds up correctly, I did want to seek your opinions as to how I should be setting the shuttle Ďpull downí cam. Clearly there is something amiss with its current setting (and thereís probably been a problem there for a while now if Iím honest as it makes a racket, looks like itíll all drop to bits at any time, and it doesnít hang onto the film as I think it should). I donít want it to go wrecking film!

OK, so attached to this post are a couple of write-ups from Bell and Howell. The first one purports to be for the 1595, 2585, 2590 and 2592 and just mentioned tightening it up until slight binding/ratcheting is heard and then back of 1/16th turn. The second is for the TQII 1652 (and others Ė several 16xx series). The second talks about all sorts of tools and I must confess I canít understand what itís getting at.

I canít comprehend why, when the mechanisms look the same between the different projects, there should be different procedures.

Any comments are of course welcome.

Thank you.
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Old 20th Aug 2019, 5:00 pm   #79
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Default Re: Bell and Howell TQII 1652 16mm projector

The 'Tools' refered to were special tools produced by Bell & Howell (that name was always Spoonerised..) for the alignment of said projectors. The manual for my 655Q shows them, but not in sufficient detail (or with dimensions) to make them which is a pity.

I think _with_ the tools it's fairly clear how to do the alignment. Without them it's going to be a lot harder. Possibly you have to work out what you are adjusting and what the correct setting should be (minimal clearance -- but some -- at some part of the cycle ; or equal clearances between parts, or...) and then hope you can do it.
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Old 20th Aug 2019, 5:05 pm   #80
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Default Re: Bell and Howell TQII 1652 16mm projector

Thank you Tony.

At least there's only one adjustment at the top of that stack, so 'steady turning and wait and see' perhaps?
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