Hawaii is the place amps come to die....or not.
I ran across a really weird specimen recently. I've been wanting to have an old Princeton Reverb to play around with but given the crazy values of them anymore I never have had the chance. This one was reasonable to get cost-wise and has some very interesting parts so I figured what the heck and grabbed it. I'll forgive the tech who hacked it up quite a bit because I think it was done a very long time ago.
It is a '65 Princeton Reverb with '65 Deluxe Reverb transformers (including the choke) and an added doghouse which seems to also come from the same '65 Deluxe Reverb based on the ink stamp in it. It was as if someone was trying to make a Princeton Reverb into a Deluxe Reverb. The tremolo Intensity pot is disconnected and the Speed pot is replaced to be a Mid control. It has a bias pot and the PI looks to be using the full fourth tube instead of just half like a conventional PR. The extra/replacement pots are dated '68. The circuit board has been cut in half in the middle, likely when the mods were done originally. I haven't tried to reverse engineer it fully yet.
I think I'll keep the Deluxe Reverb transformers in it but may take it back to a more conventional Princeton Reverb circuit and get the tremolo to go again. This may require a full replacement of the main board but I'll play with it a bit as-is first. It sounds really good and gets very loud just up to 4 on the volume control. Beyond that I am hearing a bit too much distortion (maybe some blocking distortion even) that I'm not liking too much. I want to reel that back in.
Fun project at least.....here are the pics.
'65 Princeton "Deluxe" Reverb
Moderators: pompeiisneaks, Colossal
'65 Princeton "Deluxe" Reverb
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Bryan
Bryan
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Re: '65 Princeton "Deluxe" Reverb
For the lowest level of 120 hz hum I would run a separate ground ware back to the main ground from each preamp filter, the output tube plates and screen grounds are fine the way they are.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: '65 Princeton "Deluxe" Reverb
I think that is actually kind of a cool amp. Looks like they wanted a DR inside a PR cab?
with respect, 10thtx
with respect, 10thtx
Re: '65 Princeton "Deluxe" Reverb
It's definitely leaning heavily toward a Deluxe Reverb circuit minus the tremolo and extra channel. Not much hum, but I do have a bit of idle hiss but not too bad.
My preamp voltages were on the high side so the only thing I've done so far (besides greasing pots and jacks) is swap in an 18K in place of the last 10K dropping string resistor. That gave me much closer to Fender DR schematic preamp voltages and the amp came to life much more. I'm getting smoother distortion when volume is up higher. The higher voltages make sense because this amp has 2 less tubes than a DR but same transformers. It's still about +20V high on the reverb circuit but it doesn't seem to affect the tone there. All the 100K preamp plate resistors appear to be drifted up to about 115-120K so I may replace them. I also get a weird "pop" when it is powering up after about 10 seconds so I'll probably replace the doghouse filter caps too just in case. It came with a big bottle Groove Tube 5u4 but I put in a GZ34 instead and will tune it for that.
My preamp voltages were on the high side so the only thing I've done so far (besides greasing pots and jacks) is swap in an 18K in place of the last 10K dropping string resistor. That gave me much closer to Fender DR schematic preamp voltages and the amp came to life much more. I'm getting smoother distortion when volume is up higher. The higher voltages make sense because this amp has 2 less tubes than a DR but same transformers. It's still about +20V high on the reverb circuit but it doesn't seem to affect the tone there. All the 100K preamp plate resistors appear to be drifted up to about 115-120K so I may replace them. I also get a weird "pop" when it is powering up after about 10 seconds so I'll probably replace the doghouse filter caps too just in case. It came with a big bottle Groove Tube 5u4 but I put in a GZ34 instead and will tune it for that.
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Bryan
Bryan
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- Posts: 4612
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: '65 Princeton "Deluxe" Reverb
A 5V4 works great in these also!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: '65 Princeton "Deluxe" Reverb
+1 on Stephen's 5V4 suggestion. Get a NOS one, tho.
A DR has a 220K to ground from the junction of the 3M3/470K. The Princeton Reverb omits it to compensate for lack of gain in the PI. If you put it in, the amp should clean up a bit.
A DR has a 220K to ground from the junction of the 3M3/470K. The Princeton Reverb omits it to compensate for lack of gain in the PI. If you put it in, the amp should clean up a bit.
Re: '65 Princeton "Deluxe" Reverb
I think that's what I'm looking for. I've had these two printed layouts and schematics side by side but didn't see that 220K yet. Will try this and other rectifiers! I think that may get me where I want to be.
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Bryan
Bryan