1964/1965 Fender Princeton Reverb Tech Help

Discussion in 'Amp Tech Center' started by bones11252, Jul 14, 2020.

  1. bones11252

    bones11252 TDPRI Member

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    POSTED AT TGP, ALSO GONNA TRY HERE! (HEARD THERE WERE SMART PEOPLE HERE! - Thanks Zenas!)

    I recently bought a very pristine mostly 64 Fender Princeton. The amp still has the 2 prong cord, and I am making an appointment with my tech to get it swapped. I want to be able to feel safe with it. Amp sounds excellent but I want it to survive another 50!

    If anyone can take a look at these gut shots, give me some advice on what looks to have been done and what needs to be done. I want to keep it as original as possible, but also play the thing like it was made for. Looks like a few new components, but not many. One pot looks replaced. I already but an Eminence Alessandro speaker in, came with the Pyle Driver. Any advice I will take!

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  2. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    From what I can see, it's had a 'partial' cap job. Bias cap and a couple of the electrolytics on the board have been swapped. The cap can on the underside of the amp is the filter caps, and that is the main thing you would want changed. Can we see a pic of that?
     
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  3. schmee

    schmee Doctor of Teleocity Silver Supporter

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    Change out those 3 big orange ones on the board and the filter cap can. (Silver, shows on the other side of the amp sticking up like a tube) Leave the rest. Dont let him touch those blue caps!.
    He will remove the other blue cap by the switches when he puts a 3 prong cord in. Tell him you want that cap!
    Sweet amp.
     
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  4. bones11252

    bones11252 TDPRI Member

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    [​IMG]
     
  5. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    Yeah that big silver one on the bottom needs to be swapped.
     
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  6. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Same thing any other amp needs - cap job, properly wired grounded power cord, and it's good for another 20 years :D
     
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  7. dan40

    dan40 Tele-Afflicted

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    Agree with everything the guys said. The main cap can is the original Astron can and should definitely be replaced with a fresh one. Those blue caps on the board are very hard to find these days and rarely go bad.
     
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  8. bones11252

    bones11252 TDPRI Member

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    Thanks for the advice, most of that I knew going in. I just wanted to note what was in there going in to the shop, so the same things come out! I will make sure the blue caps don't get lifted! I posted this on TGP and there was some talk of these early PT being risky.
     
  9. King Fan

    King Fan Poster Extraordinaire

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    LOL. I suspect they were talking about the fact the original ~75 mA PT works pretty hard to supply the current for this amp. Terribly unreliable; some don’t even last 55 years!!! But apparently yours is one of the reliable ones. [emoji6]

    Seriously, if there is another problem with the early BF PT here, I’m unaware of it.
     
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  10. J. Bonkosky

    J. Bonkosky TDPRI Member

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    Nice amp for sure. I would replace the bypass capacitors as everyone has said. A new grounded cable and removal of the ground capacitor is a must. I would also replace the bias supply diode with a 1000V type. I would test the multi section filter capacitor. I often find those capacitors test within specs and do not require replacement. If the amp does not exhibit 120 hertz hum and you hear no ghost notes while playing why change a good part that also happens to be somewhat costly. That is just my opinion. Thought I would share my experience you. Have fun and enjoy your new amp.
     
  11. bones11252

    bones11252 TDPRI Member

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    Yeah, here is what Zenas wrote on my other thread. Made me consider swapping the PT to be safe and keep the original if I ever sell. I am happy to get feedback from all.

    Here is a quote from the other thread:

    Then there's the power transformer. . . Mine is a 64 with the early PT, like this one there's no 100 ohm resistors off the pilot light, for an artificial center tap, on the filament winding. Muchxs a tech that knows Princeton's better than about anyone, (he's on TDPRI) advised me to swap the PT before it went up in smoke. I of course didn't, figuring it went for 50 years most of those with old electrolytic caps, surely it'd do fine with new caps. It lasted a year or two, then went up in smoke. Of course the smoke might've been a little less dramatic if I listened to the eye doctor and got bifocals! Damned 3 looked like a 1 so it had a 3 amp fuse! At any rate it shorted inside so would've been a paper weight anyway and the smoke made the rest of the guys laugh pretty hard.
    After installing a new Classic Tone PT there were zero issues with the amp, no bad tubes, nothing, the PT just gave out. Kinda figured something else caused it and me stupidly missing the 3 amp fuse fried the PT.
    Probably damage from the old Astron cap can and the over rated fuse just finally caught up to it.
     
  12. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    @J. Bonkosky - we always always always replace the filter caps. This isn't a debate anymore, so let's not take it there. We do this to save more expensive parts from dying. Caps have a 15-20 year shelf life.

    @bones11252 - I wouldn't just replace the PT for something to do. Yes, it's a bit undersized for that amp, but it's also used in the Princeton Reverb with even more tubes/current/heaters/work to do. I'd rock it out, and have done so many times, without thinking twice.
     
  13. bones11252

    bones11252 TDPRI Member

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    Mine is actually the Reverb model, thread title edited. Thanks for the info
     
  14. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

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    Congrats on your new '64! It looks great.
    Due to your questioning the smart people here, I am making the assumption you do not know the tech that will be servicing your amp.

    We do not like thinking about it, but make sure you protect your investment.

    Sometimes old stock tubes get replaced by a tech. I suggest you give new production preamp tubes with the amp. (Or let the tech use his/her own tubes.)
    You will want the bias adjusted for the 6V6s so they must be given to the tech along with the rectifier.
    As @schmee said above make sure the death cap stays with you. I usually leave them secured inside the amp, so it will not be separated at some point in the future.

    If you want to use the original PT and are concerned about it going up in smoke, you can have additional fuses installed to protect the secondaries. It is an option.:D
     
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  15. King Fan

    King Fan Poster Extraordinaire

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    Thanks for posting that. Yeah, muchxs knows a ton about PRs and has replaced a ton of their dead PTs -- when he does he smartly uses PTs with higher current ratings. But the gentleman you quote whose PT died is actually telling you something even more important -- way more: *Keep the original PT but replace the cap can.* If there's one thing in your amp most likely to kill the PT, it's the 55-year-old filter caps in the can.

    One problem with harvesting opinions from web forums is you'll get 'em -- all sorts. There are 'famous' techs who insist you should never replace a working part on a vintage amp. There are hundreds of true believers out there who think the 55-year-old electrolytic caps have some way of 'sounding better.' You get to decide who to believe.

    One other thing we learn from the post about the smoked PT -- be careful to keep your amp operating in spec. The right size fuse is vital. Run good rectifier and power tubes, set at the proper bias, in a fully tested circuit that doesn't draw more current than it should....

    You have a choice. Run the original PT until it dies -- which it may someday -- and replace it with a new one. Or replace it now for the same result sooner.
     
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  16. schmee

    schmee Doctor of Teleocity Silver Supporter

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    Well, I wouldn't swap out a good PT! Use the right rectifier tube, don't use a 5U4GB.
    It's quite likely all the tubes are good, maybe not the power tubes. If you replace the power tubes at all use JJ's. Otherwise you risk blowing a transformer because that amp likely runs real high on plate voltage. (Dont ask how I know this!) That Mullard rectifier looks just like the one I'm still using in my BFDR.
     
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  17. bones11252

    bones11252 TDPRI Member

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    Thanks for all the thoughtful and insightful posts. I just talked to a guy who lives a few hours away on the phone, who has an impeccable reputation for working on vintage circuits. His thoughts echoed many of the things I learned here. I feel very good that I am taking the right steps to be able to preserve and enjoy the amp at the same time. I didnt buy it to look at!
     
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  18. schmee

    schmee Doctor of Teleocity Silver Supporter

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    Backing off from my statement above a bit, I will say that replacing a PT isn't that hard. After you play it a while and if you are worried, installing a "fat stack" PT in that amp will not only preserve the original for that clean amp, but give you a bit more headroom if the fat stack is big enough.
     
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  19. bones11252

    bones11252 TDPRI Member

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    Yeah I figure if I ever start really pushing the amp hard, I may swap the PT. Right now I m using it primarily for recording and home use.
     
  20. Muttlyboy

    Muttlyboy TDPRI Member

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    That looks like a real nice amp...Very Clean.

    I have one suggestion which may buck the trend over here.
    If you like the amp break-up as it is now, it might be a good idea to keep the current bypass caps.

    The reason that I say this is that the Fender factory stock value of these caps is 25uf, and they pass a lot of bass.

    Sometimes as these caps age, they drop down in value, limiting some of the bass frequencies, which can help the distortion tone.

    If you will primarily play the amp clean, or using pedals for your distortion tone, then go ahead and have them changed out.

    Maybe also check around here and TGP with the Techs that post for knowledgeable opinions on any particular Tech that you'll be using.
     
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