[Central-Electronics] 20A restoration: Tuning a PS-1

[Bill Blackwell]

Good afternoon.

Has anyone tried to tune a PS-1 phase shift network?

The 20A that I am restoring has about a 150-degree audio phase shift
measured at the PS-1 output pins, at 1000 Hz. At higher frequencies it gets
worse. At lower frequencies (around 390 Hz), it's a perfect 90 degrees.

The PS-1 input voltage divider is correct at very near a 2:7 voltage ratio.
Phase shift is constant over any speech level input. So I suspect one or
more of the capacitors in the PS-1 has drifted out of tune or gone bad in
the 50+ years it has sat on the shelf.

I found, thanks to N4TRB, the issue of GE Ham News where Don Norgaard,
designer of the "SSB Jr" (precursor of the CE exciters), describes how to
tune the PS-1 in some detail. Is this the best way to go about it? I
hesitate to start clipping component leads in this little box to start
testing and tuning. The fact that lower frequencies are OK while higher ones
are not, could indicate which RC pairs I should start with first.

Is there a better way? Any help or insights appreciated.

Thanks, 73!

Bill
AB1XB