We take a close look at a great vintage classic amongst guitar amps, a vintage Fender Princeton Reverb. In this complete repair service we discover that it’s in a nice and original shape, and it has probably has never been serviced before. We change out the electrolytic capacitors, and also end up replacing the octal tube sockets after an attempt at re-tensioning the pins in the original sockets. Unfortunately these were worn out. So they had to be replaced because bad contacts can cause damage or serious reliability-issues. We chose some more heavy duty ceramic ones.
Cabinet Inspection: 0:20
Tube Side Inspection: 2:54
Circuitboard Inspection: 4:54
Service Plan: 7:00
Straightening Tube-sockets: 16:51
Power-Up and Test: 22:01
Tremolo Situaton: 24:15
The Bias: 26:44
Replacing Tube Sockets: 32:49
Final Test: 34:20
REPLACING ELECTROLYTICS, AND TREMOLO MOD
The original Blue coupling capacitors also test fine and are not leaking (yet). So while the amp might benefit in the future from a preventive replacement, it’s nice that it’s further fully original and working great. We do modify the tremolo as it is a very easy and reversible mod. The tremolo operates on the output tubes bias. The original value of 1M didn’t quite cut it, resulting in a bit of a weak tremolo, even with the intensity on 10. So what we did is lowered the value to 500k by adding a 1M resistor in parallel.
OUTPUT TUBE BIAS
We are lucky: This PT is a double-120v example and the JJ-5U4GB miraculously gives us the right voltage for a newly installed set of JJ-6v6 in the original non-adjustable fixed bias setup! Too high current draw could cause low plate voltages but it’s good that’s not the case. A GZ-34 takes it closer to the given value on the schematic anyway but the amp works great in this conservative setup. In this video I’ll show you how to calculate the bias in these.
Gotta love these vintage Fender Princeton Reverb amps, which aren’t critically altered since the blackface era. When pushed a little and played with the right touch it can give you a wide range of great guitar tones with just your attitude and electronics on your guitar!
May it please you, because more tech-mumbling content is on the way!
If you have any question’s or an amp repair request, leave a comment or write me a personal message.