8mm Forum: B&H Photo Diode

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Topic: B&H Photo Diode

Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted January 28, 2006 09:28 AM

I have just got an old B&H 643 projector running after many years of it gathering dust and cobwebs in my Garage. The valve amps needed repairing and now work well except a bad hissing from the photo diode. If the diode is disconnected from the amp all is ok and the amp is nice and quiet. The mic input is also noise free.
Does anyone have the spec for this Photo Diode or its makers number or even know where I can obtain another one or a modern equivalent.

Many thanks, Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Dan Lail
Film God

Posts: 2110
From: Loganville, Georgia, USA
Registered: Jun 2003

posted January 28, 2006 10:42 AM

Kev, Old Timer Cameras has a repair manual for the B&H 643 for £35.95, Here's the link;

http://www.oldtimercameras.com/stock/type.asp?StockTypeID=11&source_ID=50

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Simon McConway
Phenomenal Film Handler

Posts: 1085
From: Doncaster, UK
Registered: Jun 2004

posted January 28, 2006 04:08 PM

I work on Bell & Howells, just as you do with Elmos, thanks to the training of a B & H engineer I found living just the other side of town to me! Anyway, you have two ports of call. Quite a few B & H parts are available from Gordon Ogbourne 01895 638062. He advertises in quite a few cine magazines, so I'm sure he'll not object to me placing his number here. Then try Rod's Valves (search Google for the website), he may have the photodiode you need. In the meantime, I'll see what other info I may have.

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David Park
Master Film Handler

Posts: 346
From: UK
Registered: Nov 2003

posted January 28, 2006 04:12 PM

Why not click on 'Manuals' on the left and '16mm projectors' and 'Bell & Howell'
Difficult bit is decideing which of the American models is equivilent to your UK 643 model.

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Regards,
David

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted January 29, 2006 06:48 AM

Thanks Guys. I do have the manual for the B&H 641-655 series but it only gives a part number, not a description or manufacturer of the part. Its a Germanium Photo Diode and I wondered if one of the newer silicon types would work. This one makes quite a loud rushing noise when there is no light on it. I have however managed to quieten it down by putting a 12k resistor accross it (value found by trial and error) but that does reduce the sound level as well although the results are now acceptable. My thoughts are that maybe even replacements could be giving this trouble just from the age of them.
It may be an old machine but they do run well [Smile]

and warm the house up during these cold months [Big Grin]

Kev.

[ January 29, 2006, 09:11 AM: Message edited by: Kevin Faulkner ]

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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David Park
Master Film Handler

Posts: 346
From: UK
Registered: Nov 2003

posted January 29, 2006 12:44 PM

Yes good machines untill the worm gear goes, then the whole lot goes in the dustbin.

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Regards,
David

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John Whittle
Jedi Master Film Handler

Posts: 791
From: Northridge, CA USA
Registered: Jun 2003

posted January 29, 2006 05:34 PM

quote:
Its a Germanium Photo Diode and I wondered if one of the newer silicon types would work.

Yes any of the newer ones will work. Check the circuit, these things need to be "loaded" with about 5.6K across them to produce voltage. Also check that the input stage has a good cap blocking anything from getting to the diode.

The old ones were noisey and probably got worse with age, the transistors also were "leaky" as well.

But a good Si unit should work fine.

John

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted January 29, 2006 05:40 PM

Thanks John, I will give an SI diode a try.
David, I replaced 2 of the worm gears on the B&H machines to date and found it quite easy to do so it wont hopefully be a bin job. This ones worm gear still looks in great shape and the original which is good news. This seems to have been more of a problem from what I can make out on the later TQ111 machines? I think the earlier TQ1's put less work on that worm gear. Right or wrong?

Kev.

[ January 30, 2006, 03:40 AM: Message edited by: Kevin Faulkner ]

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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David Park
Master Film Handler

Posts: 346
From: UK
Registered: Nov 2003

posted February 01, 2006 01:32 AM

People say all the various models have failures. I personally have never seen a green TQ111 with a good worm. I do wonder if the black TQ111 are better, as my 2 2500 series m/cs are great and in that colour.
I think I read somewhere that another gear in metal was changed at some piont to plastic, maybe that helps, but was told this gear then wasn't as good as when it was metal.
Anyway I'm glad your m/c is fine.
Wow, changeing your own worm, sounds brave to me. Have heard of a person who did change his but m/c was out of line at the end. As the gear appears to be £30 to buy Ive useually wait untill another m/c turns up and used the £30 on that, hopeing gear will be OK.

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Regards,
David

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted February 02, 2006 05:09 AM

Hi David, I found that what you really need is lot patience when doing these worm gears. As I strip the parts down with the use of the service manual I make sure that all parts etc are marked. I also make sure that with the claw tips protruding through the gate and central to their travel that I mark using a piece of paper the position of one of the upper and lower sprocket teeth. This helps to keep it all in sync when reassembled.
I do agree though....not a job I really like doing [Frown]

Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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