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RE: Sudden change in PAS sound (recent rebuild)

Posted by petercapo (A) on March 17, 2015 at 14:24:44

In Reply to: Sudden change in PAS sound (recent rebuild) posted by oldsmobuick on March 17, 2015 at 13:10:13:

I am strongly tempted to say that the kind of changes you made provide easy opportunities for errors that might cause the problem you are now experiencing. Of course, this is not to suggest you shouldn't have done it - I did something very similar with mine.

But, you are saying that everything was fine until just the past day, in which case my thought is that some part(s) may be operating outside of its normal operating parameters and may be failing(?), though I do not have a great deal of confidence in this possibility.

If you do not have a copy already, I suggest downloading the original Dynaco manual and checking the internal voltages against the chart therein. This is best done with a variac so you can set the AC line to get 335VAC to ground at pins 1 and 6 respectively of the 12X4.

For reference, here's a schematic showing a way to remove the tone controls. This circuit is doing the same thing that the PAS X-mod units did with the bass and treble pots centered. This should work fine with an amp having a Z-in of 100K or higher. I don't recall the implications (or lack thereof) of removing the 62K and 510K in this case.

Edits: 03/17/15 03/17/15 03/17/15 03/18/15 03/18/15

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