90's American HRD in for the complaint of after being on for a hour or so, it will sometimes switch to drive mode and light the yellow LED with no footswitch plugged in. I haven't done anything to it yet except inspect the usual suspects. Nothing seems damaged or loose. The area around the cement resistors is a little discolored, but tugging on them has no effect. So far it has not exhibited the problem.
I wonder, could a dirty switch jack cause this? I can make it switch by probing the jack, so I have cleaned it, as well as the push switch. It seems to switch just fine when operating the push switch or foot switch. I must admit, I have always struggled with this circuit.
https://www.thetubestore.com/lib/the...-Schematic.pdf
I wonder, could a dirty switch jack cause this? I can make it switch by probing the jack, so I have cleaned it, as well as the push switch. It seems to switch just fine when operating the push switch or foot switch. I must admit, I have always struggled with this circuit.
https://www.thetubestore.com/lib/the...-Schematic.pdf
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