I have a pas3 thats new to me. I'm having problems with the phono section. The right side volume is alot lower than the left. Other inputs work fine. Its not the turntable. It works ok with different preamp. What should I look for to fix it?
1. A bad contact on the selector switch. Try spraying the contacts on the selector switch with electrical contact cleaner and cycling in and out of the phono mode. Sometimes a bad contact on the selector switch can cause low volume
2. The phono board inside the preamp is the board nearest to the selector switch and the RIGHT channel part of the board is the part closest to the front of the preamp. The LEFT channel usually has GREEN wiring and the right channel usually has RED wiring. If your right channel is bad take out the right channel's 12AX7 and clean off the pins and reinsert the tube. If that doesn't do it then swap the two tubes on that board and see if the problem moves to the other channel. If it does - then that 12AX7 is bad.
3. Try cleaning the TAPE/INPUT switch with contact cleaner and cycling the switch back and forth a few times.
I did some voltage checks on the 12ax7's. LT RT 1=106.5 1=102.7 2=0 2=0 3=.6 3=.21 4=0 4=0 5=11.1 5=10.94 6=126.5 6=128.8 7=0 7=0 8=.7 8=.6 9=5.6 9=5.5 Looks like the cathode section 2[#3 pin] is low for the right 12ax7. Now what do I look for? Thanks, Mark
I looked at the schematic. Pin 3 and pin 8 should read the same. I see what your talking about. The fb is going to the plate with a .05 cap and a 1.2m resistor correct? I'll trace it out and try to check values.