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Tube-rectified UL Pro Reverb?

Discussion in 'Amp Central Station' started by Deafen, Oct 29, 2020.

  1. Deafen

    Deafen Tele-Meister

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    Poked around a late SF Pro Reverb in a shop today. Power trafo dates it to 1979. But here's the crazy thing - it has a 5U4, an added 5V filament transformer, and an added choke. OT looks original.

    I can't open it up, obviously. Do you think it's safe to assume that someone has actually hacked this all the way back to a BF circuit?
     
  2. schmee

    schmee Doctor of Teleocity Silver Supporter

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    Well, just hard to say. But the tube rectifier is a plus really. You can always plug in a $13 SS module instead. But be sure it's not noisy etc if you buy it. IIRC the OT was huge on the UL... how big does it look? Was it changed? might tell you more if it's still UL or changed...
     
  3. Deafen

    Deafen Tele-Meister

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    Yeah, the OT was very big, that's why I couldn't see the numbers on it. I did see the "Fender" stamp on it, so that's why I'm assuming it's original.

    It's simple enough to replace the UL setup with a traditional screen supply, though. Trivial, for someone who's willing to hack in a tube rectifier, haha.

    I think I'll go back this afternoon with my guitar and give it a listen. The price is fair for a stock one, but this may be the rare case where some modifications might actually make it a little more valuable to me.
     
  4. Wally

    Wally Telefied Ad Free Member

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    The serial number on the chassis will tell you in almost all cases what year the amp was built and therefor whether or not it left the factory as a 70 UL Pro Reverb. If there is an A plus six digits, the second digit is the year in the 1970s starting with 1976.....A6xxxxx is 1976, A7xxxxx is 1977. The ULs were introduced in the 1970s. Th@t tube rectifier will not support the stock 2x220mfds caps in series for the first stage of a UL amp. 2x100mfds in series is maxing the 5u4s capability...maybe exceeded it. Fwiw, there are two years in the 1980s in which the handwired vintage circuits were built...1980 and 981. The serial number code for the ‘80s begins with an F....F0xxxxx is 1980.
    I am very hesitant to buy modded amps until I understand what has been done. I look at any and every Fender circuit anyways since I have seen A number of them that had their value severely compromised due to what had been done. That doesn’t mean that the amps were not good amps as they were, but they were not worth what had been paid for them as vintage Fenders.
     
  5. Dacious

    Dacious Poster Extraordinaire

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    Yeah, I had a 77 and considered doing that - but it's too different. 'Blackfacing' couldn't take this amp back really. A 5U4 will be saggier but it's still an efficient recto - the UL and bigger transformer array makes this amp sound more like a Twin. Very big and honest.
     
  6. Deafen

    Deafen Tele-Meister

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    Serial number starts with A9.

    I'd assume that the rest of the power supply was updated/retrofitted along with the rectification change. But that's an excellent point. I wonder if they'd let me pull the chassis? (Probably not, haha.)
     
  7. Deafen

    Deafen Tele-Meister

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    Good point - can't escape the beefy trafos, even if you switch it from UL to a traditional screen supply.

    Really wish I could open it up and see exactly what's up. Maybe I'll go back tomorrow and see. Can't hurt to ask, right?
     
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  8. BobbyZ

    BobbyZ Doctor of Teleocity

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    A UL says 70 watts on the back but if it didn't have a rectifier tube originally it's a UL Pro Reverb. Think they had a mid control on the normal channel as well.
    Who knows what's been done to it? Could've been someone with a Dan Torries book, he talked about adding tube rectifiers to amps without them. Not real hard, but how it was done and what else was done, who knows?
    At the end of the day a UL Pro Reverb isn't worth much and a modified one would be even less. Unless it was done by Dumble.
    If it sounds good you might toss um a super low ball offer and see what happens. It ain't like it's gonna move real fast.
     
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  9. Wally

    Wally Telefied Ad Free Member

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    Deafen wrote: “Serial number starts with A9.”

    In the case of the Pro Reverb and a number of other amps a serial number that begins with A9 might or might not be definitive. The number of digits that follow that 9 is the defining point. A9xxxx on a Pro Reverb is a 1967 amp. If there are six digits in total, then it is also definitive...A9xxxxx is a 1979 number. as BobbyZ notes, the wattages number under the speaker jacks defines the UL amps.

    If one knows what one is looking at, then one should always want to see the circuit...as I noted above. If one does not know what one is looking at, then one is at the mercy of the seller unless one takes a knowledgable person along to vet the amp. I never buy a vintage Fender if I cannot see the circuit....unless a very low offer is accepted by the seller. I never lose money on one of these th8ngs due to my caution. Caveat emptor.....buyer beware.
     
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