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Old 28th May 2011, 6:28 pm   #21
wd40addict
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Default Re: Bell & Howell 156.

The card must sit exactly where the film would be. Light should be a slit. Run the lamp off 4 volt DC then there won't be any hum!

Regards,

Paul
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Old 28th May 2011, 8:09 pm   #22
Lucien Nunes
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Default Re: Bell & Howell 156.

More than one projector I've received in the past has had its sound optics fiddled with to the point of only just producing intelligible speech. Not sure why people tinker with them because they don't normally go wrong on their own. However once you decide to experiment, your original setting (which might have been right) is lost. You can get a usable line-up on a decent commercial print but the only way to be certain is to use proper sound alignment rolls. These comprise an azimuth test and a buzz track which is modulated just outside the normal track area to enable you to centre on it.

I agree with WD, that piece of card doesn't look it's close enough the film plane to judge. Wrap a thin strip of paper around the drum, on which you should get a very narrow beam indeed.

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Old 31st May 2011, 9:10 pm   #23
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Default Re: Bell & Howell 156.

Just got back onto this.......

To sum up so far:

PJL - I can't actually see where that 'high pass filter' is in the circuit, but it's probably there.

Alistair - Thanks for the info on the liquid shoe polish etc.

WD - Using the ac supply to run the lamp was deliberate on my part as I wanted to particularly see if it would transmit the 50Hz to the PEC. You'll laugh at this - The speaker still has its front cover to protect the grill cloth during transportation/storage - when I moved things around a little earlier, I had re-fitted the cover, hence when I said the 50Hz hum wasn't that loud, well it was louder when I eventually removed the speaker cover! Whether it was as loud as it should be will remain to be seen.

I've just wound a strip of white paper round the drum & there looked to be quite a nice, sharp horizontal slit of light showing. I took a photo of it, but it didn't really show up what I wanted. I haven't touched the optical adjustments at this stage & it's looking like there may not be any need to. The picture I posted before was of the 'image' as reflected from behind the drum & aimed through the slot & into the unit for pick up by the PEC.

Seeing as my component stock dates from the 1970s & is now running rather low, I've just put an order in for a few replacement parts, capacitors, resistors etc. which will mean that I can tidy things up within the amp. I've also been on ebay to buy some new (old) cheap film, seeing as mine is now all in short lengths. I didn't get the film I wanted, but got another one that obviously no one else wanted! Anyway, should be fun & will do for a start to get a proper idea of how it's working so far. Components & film should be here sometime this week.
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Old 6th Jun 2011, 3:31 am   #24
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Default Re: Bell & Howell 156.

Well it's nearly a 'success story' now.

I received some new stock of componenents from 'Cricklewoods' - I have thousands of components, but it was getting that I had hardly any of the usual types that you need for this sort of servicing...ie, 0.00** @400 volts etc.

I received a film from a very nice man on ebay. The film is in very good condition & the seller had fitted a nice new long white leader to it which is perfect for all the threading while testing & also to see that 'slit' of optical light on at the start, too.....& all for £1.70 + postage!

I connected the exciter lamp to a nice smooth 4 volt DC supply from the bench power pack & we had loud(ish) sound - & even louder sound when (over) run at 5 volts! The sound was nice & clear, but I noted some distortion when the volume control was advanced to a higher level - this was a bit of a clue to what was to come.

At this stage, all the 'bad' parts around the PEC had been replaced. I had noted the odd 250 volt reading at the 'hot end' of various resistors while investigating this area & with the ampifier working so well with the microphone & with it being so 'lively' with hum pick up etc., when out of the case, I hadn't really given the HT supply much thought. Infact, it turned out that the 250 volts I was finding WAS the actual main HT value & not being 'dropped' through other resistors...should have checked that earlier! As I said, I don't have the correct circuit for this amplifier & there is actually a huge variation in main HT voltages between different models - variations of 100 volts, the lowest being 275 volts.

So the HT is a bit down. The rectifier is a 5Y3 (GT version) or GZ30. A quick look in the box for something similar with a 5 volt heater produced a GZ37. This was a large glass version, but I managed to shove it in at an angle good enough to make contact. This got the HT up to 270 volts - & this having a 2.8 amp heater as opposed to the 2 amp heater of the 5Y3 loading the poor old transformer. Thinking about it, this increase in HT was probably due to the GZ37 (rather than a GZ30 type) being able to pass more current, rather than indicating that the original valve was getting 'low' in emission.

Next, I have to admit to being a bit cruel... Click image for larger version

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I am totally against solid state rectifiers in valve amplifiers. I have just been in the process of converting certain of my amplifiers back to valve rectification - I 'modified' them to solid state rectification when I was 'young', as I thought it was a 'good idea' at the time, although I do have some very large valve amplifiers that have solid state rectification from manufacture. This quick mod certainly brought up the HT, but I very quickly noticed the anodes of the output valves just starting to glow slightly - [Seeing as the manufacturer of this projector originated in the USA, I'll put this in a more 'American' way "the power tubes started to 'red plate' a little" - sorry about that, I couldn't resist!]. Anyway, before going any further, I popped the amplifier back in the case & ran a bit of film through & gave the amp a very short burst of power, just enough to prove that there was now 'normal' audio level, but with the expected distortion at volume.

With the amp back on the bench, the first suspects were the two 'that' capacitors. Now although this unit all looks fairly original at first glance, it has in fact had a lot of fault finding work done on it in the very long distant past. I've found quite a few capacitors that have been 'snipped' just under the sleeving & re-soldered, so someone has had some fun many years ago. This unit is quite a difficult thing to work on as regards removing components due to where they are situated in many cases. Also, all the component leads are wound tightly round their tag mounting points for good mechanical strength before soldering (quite normal in this sort of thing) & just the way I was taught to do it when I did my City & Guilds in radio & TV back in the early 1970s. So, 'snipping out' is the best method in a lot of cases & saves likely damage from excess soldering iron heat & stress on the mountings. What I was getting round to saying was that these two caps have already been replaced in the past with a type that are usually ok - You may be able to pick them out in one of my previous pictures... I checked them anyway & they were fine.

So the bias is wrong on the o/p stage, so must be in the cathode circuitry....You'll all laugh at this - It looks like there should be a 250 ohm resistor with a 50 uf capacitor across it to deck. I think in that previous picture of the chassis underside that you can see what looks like a likely electolytic tied in place with a nice original 1940s piece of string, but where is the resistor? I looked at the rather 'un-clear' print of the circuit I was using & deduced that the cathode/s were pin 6...several connections going to the one on the chassis that I could see the most easily including that electrolytic. I lifted one end of it & tested it with the meter & it read about 68 ohms - that's leaky! I noted that it had one of B&H's secret part numbers on it, rather than any value or voltage rating. For a moment I wondered if it was some sort of dual unit combining the 250 ohm resistor & 50uf capacitor & the capacitor part had gone very leaky. It was when I followed across to the other output valve that I found that there was NO connection to pin 6 on the base - that can't be right! I then looked in the valve data book & found, of course, that pin 6 is 'not used' on the 6V6 & pin 8 is in fact the cathode - the 8 looked like a 6 on both valves on my 'fuzzy' drawing.

Having got the above sorted out, I found that what had looked like an electrolytic, was in fact a small 'choke', & pin 6 on that valve base was being used as a mounting point for that, & several other connections. I then found the 250 ohm cathode resistor mounted under a nice clamp on the side of the chassis some distance away & the associated de-coupling capacitor was a section of one of the two square 'multi-block' units & had gone competely short circuit.

The resistor was fine & with the connection removed from the bad capacitor section & a 47 uf @ 40 volts capacitor patched in its place, the HT was back up to around 320(ish) volts with the original 5Y3 rectifier valve back in place. I did give it a very quick try with the diodes & resistors still in place & had HT over 400 volts - that poor old smoothing block, how much can it take? I didn't try the unit back in the case again with this set up as I didn't want to risk the old, square smoothing block going bang - although I could have re-adjusted the resistor values on the legs of the diodes to bring it down.

So yesterday I had it set up in the front room & with the shorter range of the two lenses that are with the projector, I had a good, full screen image, from one end of the room to the other. I had 'scoped' the exciter lamp supply under load once again & was getting around 9 volts pk-pk, so around 3.2 volts. The sound level is 'adequate' at full volume, with tone (or rather bass cut) turned all the way down to maximum bass, in a normal room. It wouldn't be good enough to use in a hall full of people coughing, sniffing & fidgeting. With my 'audience' in place & having run the film through once, I then got the bench power supply & clipped it onto the exciter lamp & gave it 4 volts (which it really should be). This was better & gave a degree of volume control from the maximum level. I then gave it 5 volts for a short time & it was very much better with loads of range on the volume & tone control. This would seem to indicate that not only is it just that the exciter lamp is being 'under-run' (which I think we know they usually are just a little bit), but there may also be other parts 'lacking' slightly, perhaps in the 'optics' department, or the PEC area. Measured with a 10 Meg DVM [the first DVM that I used at the very start was actally only 1 Meg - they were both under £20 meters & probably no more than £5 in price between them & bought around the same time - proving that in this type of circuit, when it's said "to make sure you use a DVM", that not all DVM's are the same - something I should have checked first], the voltage across the PEC is now around 50 volts. I could probably 'doctor' the circuit around the PEC to 'up' the voltage across it? Or, perhaps it's the HT that is still too low for this model?

What I would like to know from the people on the forum that 'know', is - what actually does happen to the sound when the optics are out of adjustment...is it just that the sound level goes quieter? Also, am I right in thinking that the 'screw' adjustment moves the optical lense on a horizontal plane only, or does it hold the lense in place & touching it is likely to cause the lense to move about in any direction or even drop out?

I have still heard that slight 'chirping' sound at odd times (although it is a lot less & when I pointed it out to my 'audience' they couldn't hear it). I had noted that when running just a short length of film through, that the 'chirping' sound carried on for a few moments after the end of the film had past through & away from the sound pick up point - it can't have a 'memory'....which makes me inclined to think that something is being reflected from the edge of the still revolving sound drum - optics been 'fiddled' with by someone in the past do you think?

Another thing I'd like some thoughts on is that although the very old, but non-original copper plate fixed to the inside of the door (see picture below - I was thinking of removing it, but ended up just cleaning it up a bit & rounding the sharp edges - it's a bit of its 'history' after all), has an engraving, warning that with a 1,000 watt lamp fitted, the machine should NOT be run at 'silent speed'. There 'was' a thousand watt lamp fitted that I have now removed & replaced with a 750 watt version. Some of the film that was with this projector when I got it had got some nasty burn holes to some of the frames. What do you think the risk would be of trying a 'still frame' on this machine now that it is fitted with a 750 watt lamp?
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As regards the vewing experience on Saturday, it was agreed that the film that I had bought was very entertaining & enjoyable....& was probably a far better choice than the dull old 'technical' film that I had originally tried to buy. I have to admit that there is something strangely addictive about these old 'movie' projectors & I'm going to have to avoid the temptation of looking out for any more old films to buy! Perhaps it's just that it takes me back to when I used to show films for functions back in the early 1970s as evening work to earn a bit of extra cash. I used to use projectors just like this one - I certainly remember one of them was a '621' from the picture on the copy of the manual I found 'on-line'. Then I remember the later models with the built in monitor speaker & then even the ones that used to 'thread' themselves... sadly,all gone in the skip many years ago now! Having said all that, I do think this is rather an attractive projector, with its 'square' lines & black finish - & because of its age... all the ones that have 'survived' are the newer models - I think this is such a nice thing to have.

Finally, the transformer/power supply unit - I love this 'dangerous' thing! The lid can just be opened & is only held by a 'catch'. The case is constructed like a 'tank' & is of welded steel. I'm thinking of leaving the original worn & scratched paint finish & just rubbing it over with a slightly oily cloth. Also, I was wondering whether to give the voltage tapping a 'plus 10 volts', as it's set for 240 volts & my mains tends to be a bit higher than that... although that amplifier needs all the help it can get at the moment. All thoughts & suggestions welcome, pictures of/in the power pack below...
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Last edited by Techman; 6th Jun 2011 at 4:01 am.
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Old 6th Jun 2011, 8:25 am   #25
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Default Re: Bell & Howell 156.

The optics produces a slit beam. Adjust the orientation to improve the high frequency response. Any other adjustments in/out/direction will most likely increase volume.

I am surprised it works so well with DC on the lamp? It might indicate you have other 'mods' done. The light should be modulated and taken off the detector using a capacitor/resistor high pass filter. This method filters out changes in ambient light such as 50Hz modulation from the mains.

I can try to locate the setup instructions I have for mine but you really need to go in search of a service manual.

If the film stops it burns....
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Old 6th Jun 2011, 9:15 am   #26
Lucien Nunes
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Default Re: Bell & Howell 156.

With an incandescent exciter lamp, the thermal time constant is much too long to produce any kind of modulation; the normal AC drive produces zero detectable light ripple and hence it is equivalent to DC.

Clearly the valve rectifier wasn't able to supply enough current when the output stage had its cathodes dragged down by the faulty capacitor, but maybe it would do so now the amp is working normally? If you've got good HT and the exciter voltage is low, perhaps it's worth substituting its valve?

Moving the exciter optic along its axis will or rotating it will affect HF response, as both cause the beam to strike too great a portion of the film measured along its length. Moving side-side may not produce any noticeable effect on variable-area tracks unless there is heavy modulation, although it will tend to degrade SNR on variable-density. I'd still suggest leaving it alone unless there is a clear indication that it has been tampered with.

I think the speed limitation mentioned on the plate relates to lamp cooling rather than film. With the motor running at silent speed perhaps the lamphouse gets painfully hot? If the projector has a still frame clutch, make sure that the mesh filter comes in when operated. Also make sure the centrifugal safety shutter is working reliably. Look along the damaged film a few inches from the burnt frames to see if there are pulled or broken perfs or bad splices. If so, the burns probably resulted from jams rather than any fault of the projector's safety devices.

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Old 6th Jun 2011, 1:02 pm   #27
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Default Re: Bell & Howell 156.

The 'fire shutter' on these machines is actually a very light piece of metal with holes punched in it. When the machine is running normally it is lifted out of the way of the beam by a current of air. When you activate the still picture clutch a hole in the pipework is uncovered and the shutter falls into the beam. For this to work correctly the fire shutter must be a totally free fit in its guide.

When the machine is set to silent speed the fan speed, being coupled straight to the motor, drops too hence the need for the lamp wattage restriction. With the later non-blimp series the fan speed, and hence cooling, stays the same on either setting.

In fact B&H had a lot of trouble with all this and the machines were supposedly set to run at 18FPS rather than the standard 16FPS when set to 'silent'. This gave a better blast of air to lift the fire shutter and cool the lamp slightly more.

Do not attempt still frame with a film until you are thouroughly sure it's ok with no film laced. What should happen is that as you turn the clutch knob the mechanism should stop and the fire shutter will drop causing illumination on the screen to fall drastically. Note there is no synchronisation with the main shutter and it may be necessary to use the inching knob to turn the main shutter to the open position.

Regards,

Paul
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Old 6th Jun 2011, 10:29 pm   #28
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Default Re: Bell & Howell 156.

I had always assumed the AC oscillator was to modulate the light mainly as it seemed alot of parts to simulate a DC voltage. You might find this manual useful http://static.cineinformation.org/wp...ice-Manual.pdf
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Old 7th Jun 2011, 9:19 am   #29
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Default Re: Bell & Howell 156.

Back in the day it was difficult to supply smoothed DC without heavy chokes, large capacitors and a big selenium rectifier. The HF AC solution is actually smaller, cheaper and lighter.

Another solution was to use a larger wattage lamp and hope that the thermal inertia of the filament would smooth the light output. This never works as well as the HF technique.

To get a really big bulb (and thus maximum thermal inertia) some machines such as the GB-L516 used the main lamp for the exciter. Even then they had to fit a tuned 50Hz filter across the speaker!

Regards,

Paul
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Old 7th Jun 2011, 1:03 pm   #30
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Default Re: Bell & Howell 156.

Quote:
Originally Posted by PJL View Post
I had always assumed the AC oscillator was to modulate the light
No - because why would you want to modulate the light, and what would you modulate it with?

Quote:
Originally Posted by wd40addict View Post
To get a really big bulb (and thus maximum thermal inertia) some machines such as the GB-L516 used the main lamp for the exciter. Even then they had to fit a tuned 50Hz filter across the speaker!
Yes - this is a bit of really inelegant design. Let the ripple go right through the amplifier and suppress it at the output! The tuned filter was a series LC circuit, with several capacitors in place, to be linked in so that the resonant frequency was just right.

Thinking about it, this would suppress the 100Hz hum, but there will still be 100Hz intermodulation products to the audio, because with the excitation source having 100Hz optical ripple, the opto-electrical sensitivity will vary at a 100Hz rate and this will vary the audio gain at this rate.

The Bell and Howell HF exciter supply method really did have quite a lot going for it at the time.
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Old 7th Jun 2011, 10:53 pm   #31
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Default Re: Bell & Howell 156.

Sorry, meant an HF AC source. The Ampro Premier 10 uses an almost identical circuit. I guess the 60KHz frequency is chosen to keep the inductor small and still have enough gain in a 6V6.
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Old 10th Jun 2011, 1:15 am   #32
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Default Re: Bell & Howell 156.

From what that service info says, there should be a wax seal on that screw on the sound lens/slit. I suspect that it has probably been 'adjusted' in the distant past. If it was a case of that screw being an actual 'adjuster', then I could note the position & count any turns made from the original. As it happens, from reading that setting info, it talks about 'grasping' the lens unit & moving it in & out. It's only at the end that it mentions tightening up a screw - nothing about releasing the screw in the first place.

The projector is actually working very well. When running the whole film through, I tend to let it run right off the end & then disengage the clutch & leave it running with the lamp off for a short while so that the fan can cool things down a little before switching off. I had noticed that when I disengaged the clutch with the film run off the end, but the lamp still on, that the projected light on the screen went quite dim, so this is showing that the 'fire shutter' is in fact working. I didn't do this on one occasion though, as I wanted to see if it would run in reverse, which it did perfectly & played the whole film backwards without damage.

Although the projected image seems good, I notice a bit of a slight film on the surface of the removable lens from years of storage etc. & I would guess that the condenser lens may be the same. I have proper 'lens cleaning tissue', but would it be too risky to use any 'fluid' for this cleaning? I usually use a bit of IPA when cleaning such things as microscope objectives.

I haven't done any more with this projector since I last posted, but I may try to get a little more audio volume from it, although the sound is quite adequate in a normal room & about the volume that you would normally have a radio or TV sound set at - the only thing being that there is no further adjustment on the volume control to increase the volume any higher. It is running with the original rectifier valve, BTW. I think the 5Y3 is something like a 125mA valve & the GZ37 is something like 250mA, so the this latter valve was 'capable' of passing more current, thus masking the fault at first. The 5Y3 valve warms up quite quickly & I noted that there was over 400 volts HT for a few moments before the other valves warmed up & brought it down again, so it's probably a good valve still. The 6V6 oscillator valve could be down a little, so might be worth trying another. Even the 10 meg DVM will still be loading the PEC circuit, so that 50 volts could be a bit higher - I could probably take time out to work it out if I had to.

I have slightly over done the oiling as there was a nice 'hot oil' smell in the room after it had been run for a while & got nice & hot - I've mopped up any excess as it's appeared with tissue & it's stopped seeping out now. The places were only the two spool spindle bearings on the arms, but the hot smell was I think from the back of the motor on the gear box. This had a grease point, but I noticed that the grease looked rather hard & dried, so I added several drops of SAE30 to start it running again - which it has & caused a little to run out, but it isn't doing it now & at least I know it IS being lubricated & NOT going to wear the mechanism. No oil has got onto any of the film or where it runs in guides etc.

Talking about the oscillator supplying the exciter lamp, they used a circuit using two UL84s as a high frequency oscillator. It's described about half way down in the link below & suggests it was a forerunner to the 'switch mode power supply'. they also talk about running the pre-amp valve heaters from an oscillator supply, too...
http://www.schimmel.talktalk.net/cine/index.htm

Well I've now been given another Bell & Howell projector - it's a model 652 & looking at it, I don't think there will be any parts that I can use on the model 156. I went to see a former work colleague who I hadn't seen for a number of years & it turned out his son was getting rid of a load of old film gear (I was just a couple of weeks too late & had missed a stack of about seven old VHS video recorders plus tapes that they'd already got rid of).

Is this the model that has the dodgy worm drive that always breaks up?

The 652 will probably work, but I don't have the mains lead for it as it's inside the speaker cabinet which was up in their loft & they weren't able to get to it, but they said they would let me have it when they eventually dig it out....this projector is 240 volts mains without the additional transformer.

It came with a few more projectors etc. Three projectors & three cameras, so I'll soon be able to play all the various types of film at this rate, although there's a 9.5mm film there with the sprocket holes down the middle - I've not seen that before!
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Old 10th Jun 2011, 9:17 am   #33
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Default Re: Bell & Howell 156.

That's actually my website

The 652 will have the potentially dodgy worm. It's easily visible once the back cover is removed.

Enjoy your projectors, now all you need is a nice 9.5 machine!

Regards,

Paul
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Old 11th Jun 2011, 12:19 am   #34
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Default Re: Bell & Howell 156.

Thanks for all the tips & info, Guys. It's looking like this 1942 'B&H 156 GB' is now in good usable condition. Other than perhaps try to get a little more out of the audio side, the jobs left to do include - Treat the case/s with some of that liquid black shoe polish. I did have some, but it's from about 15 years ago (I use the ordinary stuff in the tins for my shoes) & I now can't find the liquid stuff, so I'll have to go & buy some more, although the new stuff may well now be better. Clean the vision optics - IPA ok on the lens surface? Run an earth wire along the outside of the original power cable between the transformer & the main unit.....probably one or two other bits that I can't think of right now.

Paul, I had no idea that was your website - you should have posted a link to it before. I just came across that page while searching for B&H info. I'll have to take time to read the rest of the pages, although I have just read the page on organs. Like me, I see you're also a 'collector' of Sound City 50s & 120s. I think you may have a point about that '8 ohm' thing - I thought it was me just 'hearing things'. I 'found' my 120 again at the same time that I found the B&H 156, they were next to each other under a load of stuff at the back of the box room. I measured 180 watts out of mine sometime about 35 years ago with 6 new o/p valves. There's only one word for the 120 & that's "nasty"! The 50s are a much 'nicer' amp. - in my opinion, anyway...I'll probably start a thread on my 'bigger' amplifiers - sometime - one day....

As for the B&H 652...or rather '8D 652' - I opened it up & blew/brushed all the dust etc. out. Then it was time for the 'bodge-block' & the deadly crock clips on the top two spades on the mains input socket which gave me the amp. & the motor........
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Then the fuse in the 'bodge-block' plug was up-rated to a 13 amp & a crock clip link added between the top left & bottom left spade & that gave me the lamp aswell. I only let it run for a few moments with the lamp as I don't think the link I was using for the lamp supply was quite heavy enough to take the lamp current for very long, but it all seems to work - the volume control pot could do with a good 'squirt', though. Would you agree that the polarity & connections are 'as I've done' correct, with obviously the earth (when connected) being the bottom right spade? It's strange why they should have the lamp going to a separate pin - there must be a link in the proper power cable plug, or is it down to the 'supposed' current capacity of the individual spade pins? Hopefully, I'll eventually get the proper mains cable with the extension speaker........
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The infamous 'worm' drive seems to be good on this one, but the application of some 'car' grease & some oil to the end bearings looks like it might be a good idea before it gets any use - what do you think?........
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Edit: There's a nice little valve amplifier in the bottom - it looks like the valve heaters are powered up as soon as power is connected to the machine & regardless of switching.

Last edited by Techman; 11th Jun 2011 at 12:37 am.
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Old 11th Jun 2011, 7:33 pm   #35
wd40addict
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Default Re: Bell & Howell 156.

That's correct, only the HT is switched. heaters are left running. Worm looks OK (for now). Lamp is on a separate pin so that a 110v lamp could be used for maximum brightness if necessary.

Connector wiring should be as follows: 13 is ground/earth, 14 is neutral, 16 is motor live and 15 is lamp live.

This connector type is known as a Jones plug. If you find an anonymous lead do check before use as Ampro used the same connector, but wired it differently!!!!!!

Regards,

Paul
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Old 11th Jun 2011, 11:53 pm   #36
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Default Re: Bell & Howell 156.

Thanks for that, Paul. I did see you had posted this info in another thread, but I can't see how numbers up to 16 can relate to a plug with only 4 pins & a locating peg?

There are no numbers on the socket that I can see - I thought the info you posted (I think I've seen it more than once recently) related to the multi-pin version as used on the old EKCO TVs as in the picture below my user name...or am I missing something?
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Old 12th Jun 2011, 2:47 pm   #37
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Default Re: Bell & Howell 156.

Goodness knows why it's numbered like this, but if you inspect the plug very carefully the numbers are normally moulded in.

Attached picture is from the 644 manual.

Regards,

Paul
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Old 13th Jun 2011, 1:03 am   #38
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Default Re: Bell & Howell 156.

Thanks for that 'interesting' diagram from the manual.

As you say, goodness knows!

That is upside down & wrong way round!

It's obviously supposed to show the wiring from behind the socket, but even then it's still wrong. I was going to remove the two screws & pull the socket forward to have a look at the rear for the numbers, but there is some sort of 'locking compound' on the screws & either my screw driver or the heads of the screws were going to snap, so seeing as I don't need to remove it for any other reason, I left it alone. I did, however, put a small mirror behind the socket & there are indeed numbers marking the pins. I could clearly see the number 14 & it was the correct way up, so it's not just a case of the socket being turned over. It looks like the 'numbers' apply to the correct connections, but NOT as they're shown on the diagram. I could only see the top two numbers, so I'm guessing that the bottom two are correct 'number wise'.

I think that when the manual was printed, someone ended up making a copy & got the negative image reversed, then someone realised the numbers were backwards & upside down, so they rubbed them out & re-wrote them in by hand before the final printing & got the whole thing round their neck - or something like that!

I made my 'test' connections by looking at the wiring & testing with a meter before applying the 'clips. Thats a good idea about that lamp (white wire) being separate so as with a different power lead & the use of a transformer a 110 volt lamp can be used - seeing as I've got spare 110 volt lamps, but no spare 240 volt ones.

So I think it's probably time to make a couple of SAFETY points here. No one should ever use 'crock clips' from a terminal block connected to the mains to make a usable power connection to a projector (or anything else for that matter), unless:
1) They are fully qualified &/or experienced in electrical & electronic servicing.
2) They are using a 'safe' supply through an isolation transformer that has the current capacity to take the 'lamp' power of a projector.
3) They are taking all the usual safety precautions associated with this sort of work.
4) They only use this as a very brief 'test' for the unit when no proper power lead is available. If no proper power lead is available for the unit, then either a 'captive' permanent power lead should be fitted in place of the socket, or the socket be replaced with a more conventional plug & socket which should be wired in the accepted conventional way for the particular plug & socket being used.

I'm sure that most of the members of this forum don't need to be told all this, but just in case there are any reading that don't know - if in any doubt, then consult a qualified person or ask 'those that know' on here.

So to try & clarify how the connections are applied to THIS particular projector (the B&H 8D 652...remember, other models could be different, I don't know), Here is a picture I've just taken of the power input socket & here are the pin connections:

Safety first, bottom right is EARTH chassis & is a green coded wire on mine.

Next, top right is neutral & has a blue coded wire at the back on this projector.

Top left is the live for the motor & amplifier & has a red coded wire connected behind.

Bottom left is the lamp live & has a white coded wire on the back.

This is the socket & the above relates to the socket looking at it from the front as in the picture below...
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Old 13th Jun 2011, 6:12 am   #39
kalee99
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Smile Re: Bell & Howell 156.

Hi, These plugs & sockets are almost impossible to find now. I replaced mine with a standard I.E.C plug. You should find that the hole centers for mounting the plug do match (if my memory serves me).
a lot of the old mains leads are perished now and had the socket "moulded on", If you manage to find an old mains lead and strip out the socket end & rewire you will need to fabricate a cover for it.
Paul.
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Old 13th Jun 2011, 11:53 pm   #40
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Default Re: Bell & Howell 156.

https://www.vintage-radio.net/forum/...pin+jones+plug
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