AB763 Bandmaster Sounds Fizzy and Ratty

[Jake1524]

another UP just under total re-assembly and boards and wires after 50 years ARE a problem just working on it now

Looks like the board is possibly conductive? Refer to post above this!

I just noticed something else that may be relevant. When plugging my guitar in I heard an odd screeching sound. When i ground the tip to my finger, it makes noise, but not consistently. Noise attached.

https://soundcloud.com/user-47032081/in ... -squealing

[Reeltarded]

Aha

I would hate to tell you what the easy fix is. It is replace the board, or go look at Dumble files where bepone has disassembled, baked, recoated and repaired, then reused board.

[bepone]

hm ok, input jacks and bad grounding, bad connection? remove them and clean oxide properly

[Jake1524]

Aha

I would hate to tell you what the easy fix is. It is replace the board, or go look at Dumble files where bepone has disassembled, baked, recoated and repaired, then reused board.

I will happily replace the board if you guys feel that’s the logical solution here!! Do you know where to source a new one? Honestly a couple hours of work doesn’t seem like a big deal after all the time spent trying to diagnose this…

[Jake1524]

hm ok, input jacks and bad grounding, bad connection? remove them and clean oxide properly

Is this based if the sound clip?

How do you feel about the readings I posted after probing the board? Do you feel that’s enough to verify the board is conductive?

[bepone]

, or go look at Dumble files where bepone has disassembled, baked, recoated and repaired, then reused board.

thx
here is the bottom isolator board, found that on many places making shorts to the ground/ chassis

cle2.jpg

cle1 (2).jpg

[Reeltarded]

Doig Hoffman probably has identical layouts premade. Might be quicker fix that way or maybe get a perf board and set your own eyelets?

Those burn-thrus need to be repaired if you reuse this set. brb

[Jake1524]

Doig Hoffman probably has identical layouts premade. Might be quicker fix that way or maybe get a perf board and set your own eyelets?

Those burn-thrus need to be repaired if you reuse this set. brb

Hmm I would rather get something premade.. just checked out his site.. seems like a good approach.

Are the voltages I posted enough for you to diagnose a conductive board? Wouldn’t this throw off voltages somewhere else in the amp?

[sluckey]

poking around on the board yielded some spots as high of 150mv.

Not sure I would put that in the category of "conductive board". Volts or tens of volts would definitely be a problem.

[Jake1524]

poking around on the board yielded some spots as high of 150mv.

Not sure I would put that in the catagory of "conductive board". Volts or tens of volts would definitely be a problem.

Ok thanks for this. Those were my thoughts, but Ill admit i got very excited about a possible solution here!