Hygroscopic and conductive Fender fiber eyelet boards
Jul 27, 2021 7:30:31 GMT -6
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Post by bluegrassdan on Jul 27, 2021 7:30:31 GMT -6
There is a well known, but sometimes debated issue of vintage Fender fiber eyelet boards taking on moisture and becoming conductive.
I was repairing a 1976 Fender Twin Reverb this week and ran into an odd issue of popping, crackling, and hissing. The usual suspects were addressed: plate resistors, tube sockets cleaned and retensioned, reflowed solder joints, recapped the entire board, and it still persisted. Oscilloscope showed the issue around the reverb driver area.
Chopsticking the board told the story. Pressing down on the board itself would cause things to worsen. Noticeable popping when the top board layer touched the bottom board.
This has been my first experience with this conductive eyelet board issue. It has been very hot and humid here in TN and the wax impregnation doesn’t seem to do enough to mitigate the problem. A few nylon spacers separating the two boards did the trick.
So, if you notice your old amplifier getting noisy during humid weather, have your amp tech consider this particular issue.
I was repairing a 1976 Fender Twin Reverb this week and ran into an odd issue of popping, crackling, and hissing. The usual suspects were addressed: plate resistors, tube sockets cleaned and retensioned, reflowed solder joints, recapped the entire board, and it still persisted. Oscilloscope showed the issue around the reverb driver area.
Chopsticking the board told the story. Pressing down on the board itself would cause things to worsen. Noticeable popping when the top board layer touched the bottom board.
This has been my first experience with this conductive eyelet board issue. It has been very hot and humid here in TN and the wax impregnation doesn’t seem to do enough to mitigate the problem. A few nylon spacers separating the two boards did the trick.
So, if you notice your old amplifier getting noisy during humid weather, have your amp tech consider this particular issue.
