8mm Forum: failed tube amp in Bell &Howell 8399

This is topic failed tube amp in Bell &Howell 8399 in forum 16mm Forum at 8mm Forum.

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Posted by Robert C. Kline (Member # 522) on February 22, 2006, 01:08 PM:

The tube amp in my 8399 was functioning perfectly well until I started a third, 20 minute film, at which point the speaker output had dropped to a level that was barely audible, even at full volume. So far as I can tell, all components in the amp are original; so I suspect that after 40+ years the culprits could be soft tubes and/or a failure of one or more of the unit's capacitors. I would appreciate any ideas out there as to how to repair this problem or a referral of someone to whom I can ship the unit for repair. Paul Ivester has suggested Ken Layton, but I don't know how to contact him.

Posted by Kevin Faulkner (Member # 6) on February 23, 2006, 01:24 AM:

The tubes tend to go slowly so I dont think it's that. It's more likely to be a dried up capacitor. Make sure you have got some muck on the sound lens etc.

Kev.

Posted by John Whittle (Member # 22) on February 24, 2006, 09:13 AM:

This is a classic example of a coupling cap failure. This happened so often with the old RCA 400 that the schematic I got from a service man had the part circled!

If the "noise" from the amp is the same, it's likely in the early stages such as the sound input to the first stage.

BTW I thought that the 8399's had the solid state amp, could it be you have a 399?

John

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