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.
Thanks! I wonder sometimes if a turret board would change sound for the worse, but guessing it would improve things. Leo Fender was as cheap as they come, so wax-covered cardboard was the cheapest way of doing it. Yet now we have people who worship at the altar of "everything must be stock, including original electrolytic PS caps and 2 prong cords...
Makes me think next time my Princeton Reverb goes in for service, this may be the cause of the hiss, pop and hum...