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Marshal TSL 60 channel switching from CRUNCH/OD1 to LEAD/OD2 problem

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  • Marshal TSL 60 channel switching from CRUNCH/OD1 to LEAD/OD2 problem

    I recently acquired a TSL 60 really cheap because it "needs a little work". Looks like I may have purchased some hacks experiment gone wrong! It was humming really bad and wouldn't switch from CRUNCH/OD1 to LEAD/OD2. Switches from Clean to OD1 fine. I replaced the screen resistors(one had fried) and tubes and the amp biases properly and sounds great but I haven't been able to determine the problem with the switching from OD1 to OD2. The OD2 indicator on the front panel won't light up(the LED is good though) but when the footswitch is connected, the OD2 indicator on the footswitch does light up but not on the amp and no actual channel switching occurs. Someone has been in here doing a lot of hacking previously. You can tell they pulled out and reinstalled numerous transistors, mosfets and one IC. The work is very crude and its gonna be tough to trouble shoot. I started doing basic tests on a few of the devices I thought might be suspect and I did find one JFET F8 that was faulty(there was evidence that it had been previously removed and re-installed as well) but replacement did nothing. Any tips on specifically which device/s could be the culprit in the CRUNCH-LEAD switching function before I go removing every one like the hack before me? I'm looking over the schematic and I'm not exactly hip to how these channel switching circuits work. Much obliged!
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