# Help debugging hum in home made deluxe reverb AB763



## MikePukmel (Jan 11, 2018)

Hi All,
I built a deluxe reverb from an AB763 schematic and layout about a year ago. Amp works pretty well considering. Sounds OK. It has a hum when I turn up the reverb knob. Pretty bad at higher settings. I never play loud, but with the input jack unplugged, if I turn the amp volume way up, 8 or 10, geta similar hum. I have an old beat up tek scope that a friend threw out, was able to get a trace across the speaker outputs. any suggestions greatly appreciated.
Thanks
Mike


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## AlBDarned (Jun 29, 2017)

There are some here that can help with that (not me), but I'd post your issue to Shock Bros.: Shock Brother's DIY Amps


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## MikePukmel (Jan 11, 2018)

Hi, thanks for the tip, will do!


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## Hammerhands (Dec 19, 2016)

If you unplug the reverb tank, do you still get the hum?

Do you get the hum from the input in both channels?


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## Lincoln (Jun 2, 2008)

Can you post up a "gut shot" of your build? Maybe one of the pros can see something that could be run differently/better. 

I struggle/struggled with hum issues on my builds too. I find with each build, the amps get quieter. Does your power transformer have a center tap for the heater circuit? If not, did you create a "virtual center tap"? Maybe just a noisy tube? Try tapping on tubes while the amp is on. If you can hear the tap in the speaker, that tube is a problem. With a chop stick, try moving wires around with the amp running and the hum at it's worst and see if you can find what effects it. Remember the "one hand" rule. You don't want to give power a path through your heart by hanging onto the chassis with one hand while poking around with the other hand.


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## copperhead (May 24, 2006)

Pull V3 with it going & see what happens ,Then try a different tube in V3 .
A couple suggestions to try to isolate the problem .


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## nonreverb (Sep 19, 2006)

Try flipping the tank around so the send/receive coils are opposite to what they are now.


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