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Wtf happened!? Princeton blackface
Old 1 week ago
  #1
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johnny nowhere's Avatar
 

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Wtf happened!? Princeton blackface

Just trying to get some attention with the title.

I could have sworn there was a thread about the Fender Princeton blackface amp wherein a discussion was swirling about the wrong stickers in some cabinets. I need to recap one of these old jewels. It pains me to have to do it, but the values of the old paper caps are all over the place and the tone is suffering. This one is stickered as an AA764.

@John Eppstein weren't you warning someone about a discrepancy in these amps some time ago?

Last edited by johnny nowhere; 1 week ago at 02:45 PM.. Reason: Typos and eye don't see I to eye.
Old 1 week ago
  #2
Quote:
Originally Posted by johnny nowhere View Post
Just trying to get some attention with the title.

I could have sworn there was a thread about the Fender Princeton blackface amp wherein a discussion was swirling about the wrong stickers in some cabinets. I need to recap one of these old jewels. It pains me to have to do it, but the values of the old paper caps are all over the place and the tone is suffering. This one is stickered as an AA764.

@John Eppstein weren't you warning someone about a discrepancy in these amps some time ago?
I'm not sure if it was me or not, but there are are discrepancies between the tube stickers and the chassis models in a number of Fender amps from that period. This was mostly due to Fender's common practice putting the chassis and the boxes on shelves, and then pulling ones at random for final assembly before shipment. During that period Fender was doing fairly rapid evolution of the circuit design in some models, so things would sometimes get mixed up.

The good news is that for the type of service you're looking at here it probably doesn't make a hell of lot of difference, as values of electrolytic caps usually stayed the same and there were few changes in those portions of the circuit. Schematics and factory layouts are readily available online for nearly all Fender amp models of that period, so just download and print the layouts for the models made around that time, check for parts that may have been changed, and then check against what's actually in your chassis. It's not really at all difficult, just a bit time consuming.

Also,. it's my impression that there were a lot fewer incremental model changes in Fender's "student amp" line (of which the Princeton was considered the flagship) than there were in the "professional" line.
Old 1 week ago
  #3
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johnny nowhere's Avatar
 

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Okay groovy. Thanks Ace.
Old 1 week ago
  #4
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enorbet2's Avatar
While it depends a lot on what you like and don't like about this amp, if you're talking about PS filter caps it's a pretty safe bet that they were originally 20 uf/450vdc since those were standard on most Fender amps for decades. The main variation from that was on higher powered, higher voltage amps where the first filters were 2 x 70uf/350vdc stacked in series for an effective value of 35uf/700vdc.

If I were you I'd buy several values ranging from 20uf/450vdc to 100uf/450vdc to determine if you enjoy the tradeoffs. Higher uf values will give greater headroom. and less noise but possibly sacrifice some "sag" depending entirely on how loud you commonly play and how hard you drive it. I strongly recommend you search for caps rated at 105C and not settle for the cheaper 85C units. If you're on a budget maybe try 20s and 100s of the 85C variety just to feel the difference but ultimately get the value you like best at 105C.

The drive in that amp is limited by the split-phase phase inverter driver stage so the difference isn't quite as profound as it is in higher powered Fenders as far as that "sag" goes but it may be just enough to give the amp a more authoritative sound, sounding less like a student amp. A Princeton modded to a Long Tail Pair becomes a respectable fire breather at substantial SPL levels. very close to a Deluxe.

Some people are squeamish about modding classics in the tiniest detail from original, but simple filter cap values is minor and easily switched back having had no negative long term effects. Reduced noise and added headroom just behaves like an amp in really excellent shape.
Old 1 week ago
  #5
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I like the blackface Princeton "because" of the cathodyne phase splitter circuit. It is a different animal than a Deluxe. And many a Princeton has gone up in flames because of inept mods of the power amp side of the circuit. If you want a Deluxe, buy a Deluxe!! They are completely different sounds...
Old 6 days ago
  #6
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Quote:
Originally Posted by UKMK00 View Post
I like the blackface Princeton "because" of the cathodyne phase splitter circuit. It is a different animal than a Deluxe. And many a Princeton has gone up in flames because of inept mods of the power amp side of the circuit. If you want a Deluxe, buy a Deluxe!! They are completely different sounds...
I suppose it is impossible to keep up with each member's "pedigree" and I won't bore you with posting it yet again and will only say I left behind "inept mods" about the same time I got pubes. One personally owned and heavily modded Blackface Princeton Reverb lasted me more than a decade and a half averaging well over 4 shows a week for the entire time. It was stolen but I assume it still works if it was properly maintained, but frankly I have hoped that one would erupt in flames for the sake of poetic justice.. ..

I noted more than one level of mod in this thread from as insignificant as an increase in MTBF via temperature rating only at stock values otherwise, up through simple capacitance increase, and only brushed on the Driver Stage as part of the explanation that only so much sag can be reduced due to the design of stock Princeton driver as a possible consequence of increasing filter capacitance values.

Hey if you like that sag then you're set, aren't you? If you wish to reduce that slightly I simply explained it is easy and eminently reversible.
Old 6 days ago
  #7
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No interest in goosing the amp, just wanting to make certain it gets the correct value of replacement caps. This thing sounds great stock.
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