Ken Fisher Modded Princeton Reverb?

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watchthedivers
Posts: 9
Joined: Thu Jun 04, 2020 12:02 am

Ken Fisher Modded Princeton Reverb?

Post by watchthedivers »

Hey all, this has popped up a few times over the last few months for sale on various sites. Not sure if it's legit but had some time on vacation and decided to see if I could figure out what's going on in it.

It looks about 90% stock princeton reverb with the major changes being where the tremolo circuit would have been.

The odd thing is though that I don't see any connections to actually include it in the active circuit. Unless there is something under the board it looks like the normal jumper feeds right from the 3rd gain stage into the phase inverter.

I've seen in various places that kens mod to princeton reverbs and deluxe reverbs was to remove the trem and add an additional gain stage... but it looks to me like maybe this was done and then removed at some point?

There is a 1.5k non-bypassed cathode resistor hooked up to the normal trem triode, a voltage divider that would feed the grid, and a coupling cap with a resistor to ground off the plate... but neither of these are connected to the output of the 3rd gain stage or the PI.

It would be super easy to lift the PI lead and attach it to the input divider and then just jumper the output back to the PI which makes me think maybe this was done an removed? I don't see how this could be functioning with the current setup even if the wires are under the board given the phase shift off adding a stage here.

Curious if anyone else has thoughts and wanted to add this for documentation.

(oh and there is some additional filtering going on too in the power section but haven't looking into that much yet)

Reverb Listing:
https://reverb.com/item/86190381-trainw ... t=86190381

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