hoffman ab763 dr help needed

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vinman753
Junior tube assistant
Posts: 87
(2/9/04 7:20 pm)
  hoffman ab763 dr help needed
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 hi guys,
i built a dr using a hoffman ab763 design. After grounhogken helped me out, it worked fine for months. Now out of the blue i get super static sound whenever i plug a guitar in. It sounds like a speaker that's torn to shreds. I tried swapping speakers and tubes to no avail.
no components are burnt and i did the "chopstick" test with no results. It is worse on channel one than chan. two.
i put it on the bench with just the rectifier and power tubes and it is quiet as a mouse. i added the PI and it was still quiet. i added the channel two tube (v2) and put in v4 and it was still quiet although channel two still sounded a little fuzzy but not too bad. as soon as i plugged in v1 for channel one you could hear the noise was there as soon as i threw the standby switch. (that makes a crackle) you could hear some hissing and when i plug into channel one it sounds terrible. again, channel two isn't nearly as bad but it too gets some crackling. To me it seems like something electrically or electronically is "leaking". Any ideas before I just start changing components out.
Thanks.
 
LooseChange
Senior tube assistant
Posts: 204
(2/9/04 8:01 pm)
  Re: hoffman ab763 dr help needed
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 With V1 removed there is no problem?? Right??
It seems to me it is channel 1 (V1) only. There are NOT many parts to check out (10 caps and reistors and 4 pots).
If the volume control on V1 is off an you still hear noise, it is probably related to the second half of the tube. Check those parts out. Report back.
 
vinman753
Junior tube assistant
Posts: 88
(2/9/04 9:45 pm)
  Re: hoffman ab763 dr help needed
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 Never mind, I found it. (hopefully). Solder connection was bad on the #1 input jacks. I guess it was making and breaking or whatever. Fixed it ...touched up here and there and now it seems fine. why it took so long to pop up is anybody's guess.
Finally get to give my new Jensen C12N a test run in it.
Not to change the subject...but what an incredible difference between that and the oxford i had in there. WOW.
 
6G6
Junior tube assistant
Posts: 75
(2/9/04 10:53 pm)
  Re: hoffman ab763 dr help needed
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 You'd think that once soldered it would be good to go forever.
Sometimes it's not, though.
Over on the Fender forum, Oxfords are generally refered to as Oxfarts. Now you know why.
 
 
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