PS-1 Bias Fluctuations

Stage & Studio
1

Running a TC Dual Wreck preamp pedal into a Power Station-1. I would hear some distortion/flubby surges randomly.
Already replaced original Ruby tubes(I believe).
Went back and forth with new Tung Sol 6L6GC
And a couple of different 12ax7’s.
Using a Bias Probe the right side tube’s bias would spike up and come down. Randomly.
With it spiking turning the amp off then back on would reset it. That is using the Ruby’s that came in it and the New Tung Sol’s.
It is only affecting the right side tube socket.
Any thoughts? I am new to amp tech.

It has 2013 REV 2 Boards in it. I recently bought it used and didn’t get any history on it.
Also the Ground Lift Switch is missing.
Little project on my hands.

2

Hey Ryan, welcome. to the forum.

There’s a single bias source to the power tube board, so if the fluctuation is only happening on one tube, and happens regardless of which tube is installed, it’s either a dirty socket, a bad 1.5k stopper resistor on pin 5 or a bad 470 ohm screen resistor on pin 4.

A missing ground lift switch means someone removed the rear panel board and broke the switch off.

Send an email to support@fryette.com with your name, address and phone number and we’re send you some parts. Most parts requests under $10 ship free of charge inside the US.

Dave

4

Thanks, I need to open it back up and check it out.