With nothing plugged into the footswitch jack the amp is in boost mode. The amp has very little volume and the Gain and Master controls have very little effect on the volume. With the footswitch jack shorted, the amp goes to normal mode and works correctly. I changed out the CA3046 for an NTE912 (twice) with no effectMarshall-JCM800-Splitch-50W-2205-Schematic.pdf
The LED lights like it should in boost mode. The voltage at the cathodes of D2 and D3 is about 4.5 volts (normal)
I've swapped out all the preamp tubes with no change, and the voltages on the preamp tubes look normal.
I've looked up threads concerning this amp and switching problems but this particular problem doesn't seem to be covered.
Thanks for your time!
The LED lights like it should in boost mode. The voltage at the cathodes of D2 and D3 is about 4.5 volts (normal)
I've swapped out all the preamp tubes with no change, and the voltages on the preamp tubes look normal.
I've looked up threads concerning this amp and switching problems but this particular problem doesn't seem to be covered.
Thanks for your time!
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