The comprehensive PRINCETON thread

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DeathJag
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Re: The comprehensive PRINCETON thread

Post by DeathJag » Thu May 30, 2019 5:57 am

Incredible. Reading that post caused a swirl of emotions, from awe to soul-level impressed to piqued to hatred to shame to guilt, and some others in between.

I can't clearly see the front panel switches, front CU needed!

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Re: The comprehensive PRINCETON thread

Post by sookwinder » Thu May 30, 2019 6:22 am

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Re: The comprehensive PRINCETON thread

Post by andy » Thu May 30, 2019 7:37 am

Here’s the best pic of my Princeton I have, as of late. I replaced the Fender badge with an “AMP” badge. Also added tilt back legs a few years ago.
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Re: The comprehensive PRINCETON thread

Post by lhwarp » Thu May 30, 2019 12:56 pm

Okay, lets give it a go here. If it's Princeton related, feel free to stick it in here! I figure there are enough folks here using these little guys by now that it makes sense to layout the collective knowledge base in one spot. Feel free to add what you have, PHOTOS, what other gear works well with them, speakers, tubes, pedals, etc. And again... PHOTOS= :-* :-* :-*
So here's mine, a SF PR, in a premium condition, barely used, as the pictures suggests. :)

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It has a booster FSW facility, indicating that it's a late 70s model. :freako:

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It even came with its original cover and shop sticker on the back panel. :blush:

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I had to replace the original square-magnet CTS loudspeaker because it simply sounded awful :squint: . An Oxford Vibroverb RI speaker proved to be perfect for that amp. 8)

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I also replaced the 117V PWR transformer for an export one from Mercury Magnetics, changed all the electrolytic capacitors, installed a pair of Bendix 5992 / JAN-6V6WGB, improved the tremolo depht and silence (throb free), the booster function (smoothness and compression)... ::)

When I had it, it sounded quite poor, after refurbishing, it sounds as expected, that is to say like the usual good Princeton Reverb : great ! ;)

-lhwarp

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Re: The comprehensive PRINCETON thread

Post by Shadoweclipse13 » Thu May 30, 2019 8:15 pm

sookwinder wrote:
Thu May 30, 2019 5:00 am
Shadoweclipse13 wrote:
Thu May 30, 2019 4:09 am
Any weird circuitry or fairly standard Princeton?
The amp is essentially a cross between a Black Face Deluxe and a BF Princeton.
A little more powerful than a Princeton, but not quite as loud as a Deluxe.

When I designed the amp I added a number of components that would be regarded as standard safety design add ons these days, but items Leo did not use because (1) he was designing to a budget or maybe (2) they were not regarded as important back then. I would rather burn out a 50 cent resistor than destroy a $90 vintage NOS 6V6GT valve.

I then also added:
- Master Volume. This allows for the input volume to be high and dirty but the overall volume to be low, through to clean input and loud output (and everything in between). I used a MV design that is basically noiseless, consists of a twin pot and 2 resistors and IMO is essential to any amp design.
- MIDS switch. This adds in a resistor that allows the mids that are normally lost in a standard Fender design to be recovered. Cost: one resistor, a couple of inches of wire and a switch.
- Rather than having two (Hi Lo) inputs, I added a second circuit, a tweed amp circuit running a 12AY7 preamp valve. (the BF circuit uses the standard 12AX7 preamp valve)
- Attenuation for the Tweed preamp circuit. There is a switch (on the back of the amp) that attenuates the preamp signal from the Tweed preamp. This basically means you need to turn up louder to get the same volume. Why? It allows one to get more crunch without tearing your ears apart.
- A switch to allow 2, 4 or 8 ohm speaker set up.
- The usual Negative Feedback on/off switch that can add some hairiness to you sound when the NFB is off.
- JUMP switch. There is also a JUMP switch between the inputs and the BF channel input volume knob. This jumps both the BF circuit and the TWEED circuits to get everything from both channels, depending on how you have set the individual channel volume knobs.

I built/designed quite a few amps prior to this. Learnt a lot along the way (with help from James).
I stopped designing after this one. (apart from the SPLASH reverb unit and the preamp/line out amp for my Rhodes electric piano).

Lastly … assuming you have run them in, you can't go past a WEBER speaker.

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That is incredible, and makes me feel funny ;) I love that you added all sorts of little mods that are not only usable, but are things that you personally wanted. The jump switch and the built-in attenuation especially!! I hope to learn enough about amplifiers that I can do some stuff like that.
Pickup Switching Mad Scientist
http://www.offsetguitars.com/forums/viewtopic.php?f=8&t=104282&p=1438384#p1438384

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Re: The comprehensive PRINCETON thread

Post by i love sharin foo » Sat Jun 01, 2019 8:57 am

I really wanted a brown foot switch for my brown Princeton, but I didn't want to spend too much. I bought a $13 Fender switch with a 1/4" plug off of eBay, a can of flat brown spray paint, the old style RCA jacks, and a brown 2 conductor extension cord. The $20 end result:
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Also, anybody who has replaced a cap can in one of these surely hates removing the old one and soldering in the new one. I found the perfect iron for it. As it turns out, mega high wattage isn't necessary. The tip design is just as important. This one is 80w but has a 10mm wide tip. I found out about it on another amp forum somewhere. I paid about $20 for it from Home Depot. I bought it online and had it shipped to the store.
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Re: The comprehensive PRINCETON thread

Post by sookwinder » Sat Jun 01, 2019 9:54 am

another trick to removing the cap-can is if it is possible use some tin snips or wire cutters to remove the can itself by cutting the tabs away.
Warning : do not cut into the can.
Then it is even easier to remove the tabs that are left soldered to the chassis, as less heat is lost in heating the can rather than the tabs.
relaxing alternative to doing actual work ...

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Re: The comprehensive PRINCETON thread

Post by i love sharin foo » Sat Jun 01, 2019 10:05 am

sookwinder wrote:
Sat Jun 01, 2019 9:54 am
another trick to removing the cap-can is if it is possible use some tin snips or wire cutters to remove the can itself by cutting the tabs away.
Warning : do not cut into the can.
Then it is even easier to remove the tabs that are left soldered to the chassis, as less heat is lost in heating the can rather than the tabs.
That’s a good tip. Thanks David!
"There are twists of time and space, of vision and reality, which only a dreamer can divine..."

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Re: The comprehensive PRINCETON thread

Post by lhwarp » Sun Jun 02, 2019 1:42 pm

Maybe it could be qualified as a "Big" Princeton Reverb, since it has the same size but with twice the power and a 12" speaker, So I post it here ??? ... I built my Paul GUILHEM Deluxe in 1993 :

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I refurbished it some times ago - circuit and cosmetics :

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Here are the performances :

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Features - front panel :

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HIGH/LOW SW selects Fixed Bias or Cathode Bias mode.
BOOST is provided to connect a FSW to activate a boost function when the amp is around the "Sweet Spot".

Features - back panel :

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The Rectiifer SW selects Valve or Diodes rectification.
The 6L6 Bal pot fine tunes the balance between the 2x6L6 output stage.
The Feedback SW activates or releases a FB loop.

This amp is intended to deliver tones from a deep clean sound to a smooth compressed expressive sound, with sustain, harmonics and controllable feedback... 8)

-lhwarp

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Re: The comprehensive PRINCETON thread

Post by Larsongs » Sat Jun 08, 2019 5:11 pm

Great Group of Princetons here!!! Mine is a recent Reissue '65 Princeton Reverb... Love it!!! I'm looking for the recent FSR Tweed with Alnico too...

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Re: The comprehensive PRINCETON thread

Post by Larsongs » Sun Jun 09, 2019 5:26 am

Larsongs wrote:
Sat Jun 08, 2019 5:11 pm
Great Group of Princetons here!!! Mine is a recent Reissue '65 Princeton Reverb... Love it!!! I'm looking for the recent FSR Tweed with Alnico too...
I bought to use mainly as a Bedroom practice & Studio Amp. Back up Amp for 65 DRRI & Twin Reverb... But, I use it more than those other 2 including playing out...

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Re: The comprehensive PRINCETON thread

Post by kosmonautmayhem » Sun Jun 09, 2019 6:27 pm

So much good stuff in this thread already... :?

My current and likely final pair of Princetons.

'64 6G2 and '72 PR.
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Both have Webers. PR has a 25W 10F150-T. Perfect for this amp. No speaker dope either. Original was shot and I flubbed a recone and sort of gave up. The Weber sounds amazing and I doubt (vintage Jensen C10N aside) that I could do any better than this speaker. The 6G2 has an early 2000s era Weber labeled C10N that I got off TGP a decade or more ago. I believe its the pre-cursor to the 10F150 family. Its a little different than my newer one but sounds amazing and really great in this amp too. I tried a bunch of stuff, including alnicos, vintage speakers, but I always came back to this one so it stayed.

I've recapped both and added an adjustable bias pot (totally reversible) to each. Helps keep the tubes humming properly and keep the trem depth where I like it. Speaking of...I did a little trem mod to the PR a while back.

The result: https://www.youtube.com/watch?v=J_BI3hlDkxw

I've had a lot of brown ones come and go over the years but this PR is my first and last. I got from a guy who lived in Marina City in Chicago. AKA, Wilco tower. AKA Corncob buildings. The 6G2 was also my first brown-era Princeton and the one that outlasted them all.

Are there better amps than Princetons? :-*


(Ugh, I need better pics. It's almost embarrassing. Also need to dig out the pics of the long gone brownies too. :blush: )

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Re: The comprehensive PRINCETON thread

Post by i love sharin foo » Tue Jul 23, 2019 5:20 pm

I just plugged in the 6G2 for the first time in a few weeks as I've been using the '65 non-reverb a lot lately..... and it sounded like garbage! The volume output was good but it was super distorted and gated and all around terrible. I swapped every tube but the rectifier with no change. So I reluctantly pulled the chassis. After making sure everything was discharged completely, I started to look closer. And there it was... a chassis ground that I reworked had lifted from the chassis entirely! At least it was an easy fix. I got to use the new 80w Weller with the gigantic tip. It is ridiculous how easy those grounds are with it! Money VERY well spent! I reheated the two joints on the cap can as well. I also have been sitting on my pair of Raytheon output tubes for a while now and figured this was the time to swap them in. I am sitting right at 380 volts to the plates and have them both biased within range with.... wait for it... a 27k resistor hehe. I stuck a 100v 50uF Sprague in the bias circuit as well. I think it should be good to go for a while now.
"There are twists of time and space, of vision and reality, which only a dreamer can divine..."

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Re: The comprehensive PRINCETON thread

Post by kosmonautmayhem » Tue Jul 23, 2019 7:16 pm

Well done! Glad it was an easy fix. I've been there a lot with my PR. Amazing the stock 27k resistor biased perfectly. 8)

Good reminder for me to invest in a gigantic iron for the chassis. I'm sure it was a breeze with the high wattage and a big tip. :D

Did you notice any difference in bass response with the 50uF cap vs the stock 25w? I went with a 100uF in my PR but kept the 6G2 stock. Can't really hear any benefit one way or another.

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Re: The comprehensive PRINCETON thread

Post by i love sharin foo » Tue Jul 23, 2019 7:45 pm

kosmonautmayhem wrote:
Tue Jul 23, 2019 7:16 pm

Did you notice any difference in bass response with the 50uF cap vs the stock 25w? I went with a 100uF in my PR but kept the 6G2 stock. Can't really hear any benefit one way or another.
I didn't get to play much after the surgery, but I don't think it really makes much difference, based on where it is at in the circuit. I am so happy that I was able to track down the problem so quickly :) That is surely a testament to an old school, non-pcb amp. Tomorrow I am planning to give it a good run through to see how these Raytheon sound. My daughter was in the basement as I was finishing up. She was asking what everything did. Imagine trying to explain that a certain capacitor helped smooth dc current after is was converted from AC to an 8 year old :fp: We had a good talk about safety though.
"There are twists of time and space, of vision and reality, which only a dreamer can divine..."

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