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Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details.

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Old 21st May 2022, 7:22 pm   #1
didordure
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Join Date: May 2022
Location: Toulouse, France
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Default Bell and Howell Filmosound 592 valve amp help.

Hello, I subscribed to ask if by any chance someone here would have the service manual of the Bell and Howell 642 16mm Projector.

https://ian-partridge.com/bh_642.html

This has a tube amp has two row of tubes :

upper row = EF86 - EF86 - EF86
lower row = EL84(6BQ5) - EZ81 - EL84 - EL84 - ECC83(12AX7)

the downer row is the EF86 used probably as preamp for the mic input and/or the light cell (for optical sound) and the upper is the rest of it.

Does someone have a schematic of this machine?

I don't know if it works I don't want to fry anything if someone one day put the tubes back in the amp without watching where is what.

It seems strange to see 3 EL84...
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Old 21st May 2022, 9:39 pm   #2
kalee20
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Location: Lynton, N. Devon, UK.
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Default Re: Bell and Howell Filmosound 592 valve amp help.

It's possible that one of the EL84's is used as a high frequency oscillator, to drive the sound exciter lamp. 50Hz is no good because the light will vary at 100Hz rate - it needs to be either DC or high frequency. And HF was often easier than having metal rectifiers and smoothing.
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Old 22nd May 2022, 12:13 pm   #3
G.Castle
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Location: Swaffham, Norfolk, UK.
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Default Re: Bell and Howell Filmosound 592 valve amp help.

Have you contacted Van-Eck video services? They may have what you are looking for and will provide a PDF for a small charge... (Search Van-eck.net).

Last edited by G.Castle; 22nd May 2022 at 12:15 pm. Reason: typo
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Old 22nd May 2022, 4:50 pm   #4
wd40addict
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Default Re: Bell and Howell Filmosound 592 valve amp help.

Are you sure it's not a 642?

https://www.vintage-radio.net/forum/...d.php?t=160152
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