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amp circuit board burned


mbengs1

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the last time i had my amp fixed it was becuase the amp was plugged into the wrong voltage. it was 110v and it was plugged in 220v. the tech said the circuit board of the amp was slightly burned. is this part irreplaceable? is it easy to fix a burned circuit board. what are the chances of the circuit board frying? i had the amps voltage changed to 220v so i assume the amp burning again will never happen. what can i do to avoid the circuit board burning?

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No its not easily replaceable. You can buy the entire board but it may be as expensive as replacing the amp. Making a new board then moving the components over again would be a job for a tech familiar with etching circuit boards. Cost = Very expensive.

 

Most circuit boards are made of fiberglass which is spun glass and epoxy for the most part.

The boards are highly temperature resistant - up to a point that is. Slight discoloration when the board turns brown usually isn't a problem.

 

If they heat enough to turn solid black then you got problems. The board carbonizes, becomes conductive, and components arc across the board and short out. I had one amp I repaired where the amp was out of production and the power tubes kept shorting out. I dremiled the scorched parts of the board away then built new traces to span the gaps.

 

When I was done two of the tube sockets were essentially free floating. The new traces were made of heavy duty copper so there was a sturdy support for the tubes, and the amp worked as well as ever, but seeing it with the board cut out wasn't exactly pleasing to the eye but it was electronically sound. The company I worked for didn't have the means to etch a new board and replacements weren't available. I could have also cut the section out and glued a new piece in its place but it was a second repair for the same thing and I wanted to be sure it wouldn't arc out again do used bridge work instead.

 

The owner was happy with the work and since it didn't cost him anything the second time around I let it go back to the owner that way. I wasn't especially proud of the work but I did hear form the guy years later and heard the amp was still working fine.

 

As an added note, is its just surface scorching, you can usually sand it away then reseal the board with a special poly spray they put on boards to prevent moisture. High humidity and dust are the reasons many of the boards arch out because that stuff sits on the surface and arcs out.

If the board is cooked all the way through, its only a matter of time weather it arcs or not. If the scorch was in the AC voltage area I don't suspect the issue to expand like it would in the High Voltage B+ area or where the tube sockets and resistors heat the board, so you may be perfectly fine.

 

In any case you cant do a darn thing about it so forget it. When the amp goes buy a new one or sell it now while it still has value and get another amp.

 

I wont but a circuit board based tube amp myself. If the tubes sockets aren't chassis mount I'll pass. You have too many issues with the heat from the tubes hearing up the boards and causing the solder to weaken and crack, Support for the weight of the tubes sucks too. The vibration transporting the amp and vibrations when the amp is in use just make them a problem waiting to happen. Of course the production costs make them much cheaper and they usually do last a few years.

 

If I did have one I'd redo all the solder joints and add additional support for vibration and heat dissipation. If it was a 50W and up tube amp, I might even add a fan to keep the board cool.

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