FDP Forum / humm from Hell/ 5 messages in thread.

1 to 5 of 5 shown.


Roly

Contributing Member
**********
**********
*

Whitehorse Canada

I don't get out much
Dec 15th, 2017 12:22 AM        

Blues Deville.<br /> <br /> Hums like hell when taken out of standby.<br /> Pull the rectifier....amp is quiet.<br /> <br /> Used Steve Dahlman's nifty tool to extract audio and send it to a practice amp.<br /> Hum from hell.<br /> Pull all tubes...humm from Hell when using Steve's tool. With a few exceptions, the hum is ubiquitous.<br /> Haven't checked yet, but could heater voltage be leaking into the audio path?<br /> If that was the case.....shouldn't there be smoke? <br /> <br /> Any thoughts folks?<br /> cheers<br /> <br />



pdf64



UK

Dec 15th, 2017 06:45 AM        

What do you mean by 'pull the rectifier'? It's not as if it's a tube in this amp.<br /> <br /> So there's big hum through the speaker when operated with power tubes removed?<br /> If so, maybe a short in the OT or the power tube plate circuit, perhaps the protection diodes CR24, CR25; have you checked for shorts with a meter?<br /> Good luck!



Roly

Contributing Member
**********
**********
*

Whitehorse Canada

I don't get out much
Dec 15th, 2017 02:43 PM        

Hi Peter<br /> Thanks for catching my error.<br /> I meant phase inverter.<br /> <br /> I get hum everywhere with all tubes pulled when extracting audio and amplifying it with a practice amp.<br /> <br /> cheers



pdf64



UK

Dec 16th, 2017 03:55 AM        

Ahhh, ok, I see.<br /> So with just the phase splitter V3 and power tubes in place, what happens to the hum?<br /> How about if you plug into the 'power amp in' jack?<br /> Can you get a 'clang' out of the amp if the reverb is turned up and you give the tank a little knock?<br /> <br /> Have you checked that all circuit common 0V connections to the amp chassis are good?<br /> <br /> And that there's a 0 ohm resistance between all 0V points on the pcbs and the chassis?<br />



SonicBlue



Sunbury-on-Thames

Dec 16th, 2017 05:33 AM        

..<br /> <br /> whoops, wrong post



Copyright 1999-2003 Fender Discussion Page, LLC. Visit the web site at http://www.fenderforum.com