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PostPosted: Wed May 25, 2016 4:52 am 

Joined: Wed May 25, 2016 3:21 am
Posts: 1
Nice amps!

Thought I would post some findings re the above amp if, for nothing else just to comment and give you some feedback for the future perhaps and help others.

I have seen 3 of these amps now and they have all had the same sort of issue.

Symptom.: Random popping, rumbling loud bangs on audio, even with all channels 0 volume. The fault has been around the send FX buffer transistor cct Q5 and associated components. At first I thought it strange that a high voltage emitter follower cct was used just to provide a volt or so for the FX send. But, I guess that given there are not analogue low supplies (+15V for example) are available. I have found that there is electrical leakage or tracking within and or on, the board around Q5. Cleaning and resoldering the board does not cure the fault. Each time, I have had to recreate the cct, 4 resistors and Q5, suspending this on stand-offs, with 47K resistor removed from the main board. All works fine and the background noise is greatly reduced.

Secondly, I have found the the main PCB has been cropped very closely when the component lead outs have been finished. It looks like the PCB has not been even on the cutting bed. As a result, a lot of component on one side have had their leads cut so close to the board, that the soldering in almost non existent. This causes faults as the board gets hot.

Thirdly, I have had to replace the non polorised cap in the -ve feedback cct. This seems to break down causing odd effects.

So there we go! the Q5 fault took me hours to get to the bottom of.

I hope the above is of some help to you guys.

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PostPosted: Wed May 25, 2016 8:29 pm 

Joined: Fri Jun 22, 2007 2:18 am
Posts: 1545
Location: Phoenix, Arizona
I literally understand nothing about what you said

but if i had a combo tube amp and it was poping and rumbling...
i'd spend $20-30 and get a new reverb tank

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