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Blackface Princeton NR service project

Discussion in 'Amp Central Station' started by PrinceTonNR, Apr 14, 2021.

  1. PrinceTonNR

    PrinceTonNR TDPRI Member

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    Greetings,
    new to TDPRI and thought I'd kick it off by showing pics of my Dec 1965 Princeton.
    I live in Stavanger on the SW coast of Norway. I bought this amp on a business trip to Houston some 20+ years ago. The amp has not been used at all for the last 15 years. Now it is time to get it serviced so it can accompany my guitars again.
    The amp is pretty clean but my findings so far are:
    Sticker stamp: OL
    PT: week 48 1965
    OT: week 39 1965
    Chassis serial: A 06856
    - the amp underwent service in 1974 or later; The Mallory Can cap dates week 22 1974 and the speaker has been replaced with a Fisher (1056) 10" (dated week 17 1974).
    My plan is to replace the can capacitor, get rid of the death cap and add a 3 prong mains lead.
    As we have 230V I will be using an external step down transformer.
    Here are some pictures:
     

    Attached Files:

    Torren61 and King Fan like this.
  2. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Nice! Very good project. The amp looks to be in amazing shape.

    Besides doing the cap can, 95-99% of the pros here would suggest replacing the other electrolytic caps, especially those paper canister ones. Their useful safe life is long over. If you want, tho, it’s easy enough, and actually fun, to keep the canister and 're-stuff' with a new cap for visual appeal. Let me know if you’re interested—I have some good links somewhere.

    Re the cap can, do you have an 80W+ soldering iron with a big tip and heat reservoir? Worth getting. Can you get the CE Mfg. cans in Europe? If so, they’re nice — made on the original vintage machines.
     
    Torren61 likes this.
  3. Torren61

    Torren61 Poster Extraordinaire Gold Supporter

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    REALLY nice amp. One of the classics. Very clean and original looking. I bet you didn't pay anything close to the $3000-$4000 they sell for today.
     
  4. telel6s

    telel6s Tele-Afflicted

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    Nice. I've had a '71 Princeton NR for about fifteen years. It could probably do with a tech looking her over. I could easily be wrong but I don't think the circuits on these small amps changed much if at all between BF to SF or Fender to CBS.

    I get the whole thing about Princeton Reverbs these days, but I feel the non-reverb versions are often overlooked since they don't have the extra reverb gain stage. But I love an amp I can just set on "10" and not worry about blowing out a room. P90s are my favorite pickups with my Princeton.
     
  5. Wally

    Wally Telefied Ad Free Member

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    Welcome, PrinceTonNR. Nice amp to own...Reverb.com puts at $2200-4500 USD.
    Imho, you have a decision to make. I would consider pulling that original PT and installing a Hammond 290AEX with international primary and enough current handling ability to deal with that amp. The stock PT is not really the best choice for the application. Should it burn down, that amp loses a lot of value. And...they have been known to burn down when subject3d to demands that we put on them these days. These amps were built and sold as beginner practice amps rather than professional use amps. If 9ne never puts the amp to hard work, perhaps all is well. That PT is the same PT that was used in the little .champ, VibroChamp, and Bronco...as well as the Princeton Reverb. The Princeton Reverb puts more demands on the PT than does the Princeton, but....????.
    IF the PT were designed to handle all that might be demanded of it, I certainly would not consider replacing a healthy PT. You might not want to, and you might never put demands on the little amp. If you were to decide to pull it for preservation, one might want to document with pictures that indeed this particular PT is the one that came in the amp and was replaced for preservation. Your need for a different primary is an added explanation for replacement.
    Is this approach excessive caution??? Maybe. I advised a fellow with a 1964 Princeton Reverb about needed work on his amp. He decided not to do anything. I replaced the blown PT 1 1/2 years later. Luckily, it was only a chassis which was not in the original cab.
    I recently put this 1972 Prin Rev back in action. This one has the later PT which has more current handling capability and internati9nal voltage primary. Yes, I had to [email protected] the grille cloth.
    985944FE-95D4-4AE3-A71E-2FE2478CB012.jpeg
     
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  6. PrinceTonNR

    PrinceTonNR TDPRI Member

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    An update:
    The old Mallory caps need to be replaced and to keep the original look I decided to replace the innards with modern Sprague ones. Here are a few pics illustrating the job.
     

    Attached Files:

  7. Wally

    Wally Telefied Ad Free Member

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    To the eye of an experienced vintage amp nut such as myself, there is nothing about that replacement cap that looks original. I know immediately that the cap is not original. It does look like it took more work to do it that way, though.
     
  8. PrinceTonNR

    PrinceTonNR TDPRI Member

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    Thanks, can you explain what deviates from the original?
     
  9. Wally

    Wally Telefied Ad Free Member

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    I would hate to ruin it for someone who thinks that this looks original. (;^). Without a doubt an experienced eye will see immediately that it is not original. It has nothing to do with that cardboard cover.
    The other side of the coin is that imho it is better to reveal the work because anyone who knows vintage amps and is going to play a vintage amp wants the amp to be in proper order. That necessitates certain work, and that work does not lessen the value of the amp. In fact, if that work is well done, it makes the amp more attractive because one does not have either to do the work or pay for the work to be done. The amp is ready to go to work.
    pin order for me to know that the work was done the way I would want it doen with the parts that I would prefer would be to see those parts....not a 50 year old cardboard cover. Ommv....and that does not confront me.
     
  10. PrinceTonNR

    PrinceTonNR TDPRI Member

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    Mother/daughter thing. Your opinion is as valid as others’.
     
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  11. PrinceTonNR

    PrinceTonNR TDPRI Member

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    For anyone interested, I am happy to report that the amp is alive again.
    Electrolytics replaced with Spraugue ones. Can capacitor upgraded to 40/20/20/20 @ 525V.
    A 100K pot instead of the 27k resistor in the bias section makes biasing easy. Apparently the two 6V6GT’s are not quite matched so am running one hot (ca. 23-24mA) and the other cold (ca. 17-18 mA). «Death« cap disconnected (but left in it’s place).
    Pots cleaned, all solderjoints checked.
    3 prong lead and stock PT.
    I have to say I’d forgotten how well this little amp sounds! It doesn’t start breaking up before the volume is set above 8 but for my use it is great.
     

    Attached Files:

    Last edited: May 8, 2021 at 6:48 AM
    stevemc likes this.
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