Discharge high voltages before you start work on any amplifier. This is how you do it.
I use a 1Kohm, 1 Watt resistor to short across the power supply filter cap. We want the voltage to get down to less than one volt. It might take a moment to discharge the cap. Check the voltage with your DVM before you try any of the mods. You can now safely partially remove the PCB from the chassis.
The chassis is on the bench and the PCB is partially removed so we are ready to actually start the mods.
The tone stack mod replaces two caps in the tone stack itself and two coupling caps.
- C6 0.1uF Bass
- C7 0.015uF Mids
- C2 0.022uF Input Coupling
- C8 0.022uF Output Coupling
For me, the easiest way to change out the components was to locate the part then highlight the hole on the solder side of the PCB.
Past experience taught me that the best way to get a component out without damaging the PCB, traces or holes is to use solder wick with flux applied. Just add a quick touch of the solder iron and it all comes out nicely.
I do recommend to cut the capacitors off on the component side first if you don't want to preserve them. For me, I wanted to be able to go back to the original if I didn't like the results of the mods so I took the extra step and preserved the caps.
The caps are all in place and it is time to move on to the next step. Next time we'll apply the power supply stiffener and the bias trimmer.