Princeton Reverb II only! If it ain't got the II, this page ain't for you.
Fender Princeton Reverb II
Modifications

Most frequently-asked modification questions;

"Why is the reverb all mushy and unusable above 3?  Quick answer (a) because you've probably got the side-mounted version. Relocate it to the base of the cab where it belongs, ie horizontal not vertical.  And (b) because the reverb unit is driven too hard in these amps. Find a way to cut it down (may be as simple as turning down the front-end volume and turning up the master, or putting a weaker tube like a 12AX7 in v2).  MY reverb isn't mushy, so there.

"Why is the lead sound so nasty?"  No one answer will please everybody but (a) try the most expensive valves you can afford in v2 and v3 (b) read this

"Why does the reverb drop away when I select the lead effect?"  This isn't good but it is normal, I'm afraid. Read about v2here.

"Where is the legendary Rivera tone circuit which is only selectable with the footswitch?"  Quick answer: there's no such thing; it's a myth, not put around by Fender.

"Can I install an effects loop?" The quick answer is, "yes, but it would be really difficult". I don't know anyone who's done it. It would require some new design work, new circuitry, and major surgery. A variation on the question is "can the reverb send-and-return be converted to an effects loop?". The quick answer is "yes, but it's still not a 5-minute job." The levels and frequency response of the 'send' are all wrong. The 'return' might need some work too. I usually ask, "why do you want one? Isn't the PRII quiet enough to put pedals etc into the front end?"

What's the Hum Balance for? (a control on the back panel) Technical answer - it provides an adjustable ground reference for the valve heater circuit. So there. It has nothing to do with the valve bias. Practical answer - If your PRII isn't humming, leave the Hum Balance control alone. If your PRII is humming, take a flat-blade screwdriver and turn the control one way and then the other. Leave it at the point of minimum hum. If there's still an irritating level of hum, something else is wrong.

How to dismantle the PRII
RELIABILITY MODS including simple cheap cooling fan
TONE MODS
VOLUME, GAIN AND DISTORTION MODS

SPEAKER DIRECTIVITY CURE (JAY MITCHELL FOAM DONUT)
INSTALLING TILT-BACK LEGS
HORRIBLE MODS (DON'T GO HERE)

COMPLETE TESTED REBUILD TO SOUND MORE LIKE A DELUXE

MULTIPLE USEFUL MODS BY JOWES_84 ON THE TDPRI (new June 2020)

INTERIOR PHOTOS for reference
PRII home

email me... stratopastor (at) hotmail (dot) com

IN GENERAL I AM SUSPICIOUS OF MODIFICATIONS and I prefer only to list mods which have actually been done. I don't like listing mods of the "I heard from this guy once..." variety. Nor do I  like the attitude "no-one at Fender's R&D knew anything and an amateur with a DMM on his kitchen table is more likely to get something right...."

As with all the other pages on my site, the details are believed correct but I won't take any responsibility for what happens if you attempt them. Valve/tube amps store lethal voltages even when switched off and unplugged from the wall, and if you don't know what you're doing, you can be badly hurt.

If you have tried any modifications, I would be delighted to hear from you - even if you're not satisfied with the result, it's useful information for the rest of us! I'm specially interested if you've converted to cathode bias, converted to tube (valve) rectification,added a sag resistor, or added a triode-output switch.


PRII home
rebiasing
dismantling