Monday 20 February 2012

Part 5: Testing the PP-18

Although all the voltages checked out OK, there was something not quite right. One of the pots weas a bit scratchy. That was replaced but there was still a serious problem. The EL84 valves were "red-plating". Not good. This is not a good sign with any valve amp, so it was head scratching time.

Not only that, but the volume simply wasnt there. 18 watts is supposed to be loud....

Careful checking of the wiring revealed that the tone control / volume pot wiring wasnt quite right. I cant remember which one it was, but a wire was going to the wrong place and that was what was causing the anodes to go red

A quick bit of desoldering and resoldering and , bingo, problem gone. I plugged in the Tokai Strat, turned the volume a little bit - DEAFENING! Man what a sound.

So the moral of the story is - check check and check again. And then probably again just to be sure.  Its probably worthwhile checking it again first thing in the morning after a good nights rest. Sometimes the brain just gets tired and cloudy and you just cant see the problem. After a good nights sleep it is obvious!

Anyway, that was all the electrical stuff done - next stage was finishing off the case.

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