Earlier this year, I bought this '67-'69 Univox U305R: twin 7591s, 6CA4 rectifier, two channels; 3X12AX7s; input/volume, tremolo oscillator, and output driver, and a 6AN8 and a 6AV6 for reverb drive and recovery. The reverb, like an Ampeg, is resistor/capacitor-coupled not transformer (Fender/Gibson) or speaker (several Guild models) coupled.
Schematic - Shows 6973s but 7591s in this model:
Tube deck view - note exposed lugs on output transformer in the left-center, a tell for off-shore gear. US mfrs always have bell ends on transformers with leads coming out. Reverb to / from pan in lower left; we appreciate the big cut-out that the transformer straddles because .....
Without it, there would be no access to the printed circuit board traces below. These were the achilles heel of many of the later 60s amps. Even if a bad part was identified, getting it off the pcb and a replacement in depended on getting lucky; that you could get a soldering iron on the trace side to disconnect and replace the defective part. If that wasn't possible, then all of the lateral connections on one side had to be disconnected to flip the pcb up on its side. Not hard to imagine how many repair estimates were refused because of several hours of labor being needed to replace a $.15 part. Note open lugs on power transformer at right of pic.
Bonus! 15" Jensen/Muter C15PS Special Design speaker. The frame side was coated today with Metal Ready; a solution containing phosphoric acid to prep rusty metal for painting; in this case, some mild rust on the up-facing side of the frame, otherwise in fairly good condition. These were standard-grade commerical speakers of the day; popular with many manufacturers; dates to 15th week of 1967, probably, but not necessarily, original. Cone and gasket in good condition.
Right now, you're probably asking yourself 'why on earth would anybody screw with one of these?' ... it's a reasonable question. Our BBer matsickma is a big fan of the 7591 tube as are Gilded and Mad Dog who both own/have owned Ampeg 7591 amps at one time or another. The thing is that there are no Guild or Ampeg 7591 amps here in the rock 'n roll wastelands of south FL which means that, in addition to buying an amp unplayed, it'd cost another $100 in shipping just to spin the wheel of fortune.
This one showed up on Craigslist and, in addition to the 7591s, I got reverb and a 15" speaker for an hour's drive up the coast to Fort Pierce. I also lucked out in that, right after I got it here, a dual Univox footswitch showed on eBay so it's got all its pieces and parts and, although you can't really tell by the pics so far, it's in pretty good condtion ... be nice if it sounds good too. I've had it running and it passes a signal; needs a reverb pot, both reverb tubes, and the unavoidable power supply and cathode caps; all the parts here, no biggie but but but but but.....
May have been played by Elvis!!
That's right folks! Tom Petty was born in N. FL in 1950; was 17 or 18 about when this amp was manufactured. Somebody ... maybe Petty-Daddy ... used one of those electric etching pencils to inscribe the name 'Petty' into the back chassis panel. The seller told me that the guy he bought it from told him that the amp had been Tom Petty's.
Being a Guilder, I discounted the claim but, at some point, I'll probably see if I can contact him ... who knows, if it was his, he might like it back ... In the meantime, I'll have something cleaner and brighter for the Rickenbacker to work with; ok w/ the Gibsons at low volume but when pushed ... the Rickenbacker bite gets lost in the Gibsons' distortion ... it sort of mushes out... so ... we'll see ... anyone got Tom's name in their address book? :lol: CJ
Schematic - Shows 6973s but 7591s in this model:
Tube deck view - note exposed lugs on output transformer in the left-center, a tell for off-shore gear. US mfrs always have bell ends on transformers with leads coming out. Reverb to / from pan in lower left; we appreciate the big cut-out that the transformer straddles because .....
Without it, there would be no access to the printed circuit board traces below. These were the achilles heel of many of the later 60s amps. Even if a bad part was identified, getting it off the pcb and a replacement in depended on getting lucky; that you could get a soldering iron on the trace side to disconnect and replace the defective part. If that wasn't possible, then all of the lateral connections on one side had to be disconnected to flip the pcb up on its side. Not hard to imagine how many repair estimates were refused because of several hours of labor being needed to replace a $.15 part. Note open lugs on power transformer at right of pic.
Bonus! 15" Jensen/Muter C15PS Special Design speaker. The frame side was coated today with Metal Ready; a solution containing phosphoric acid to prep rusty metal for painting; in this case, some mild rust on the up-facing side of the frame, otherwise in fairly good condition. These were standard-grade commerical speakers of the day; popular with many manufacturers; dates to 15th week of 1967, probably, but not necessarily, original. Cone and gasket in good condition.
Right now, you're probably asking yourself 'why on earth would anybody screw with one of these?' ... it's a reasonable question. Our BBer matsickma is a big fan of the 7591 tube as are Gilded and Mad Dog who both own/have owned Ampeg 7591 amps at one time or another. The thing is that there are no Guild or Ampeg 7591 amps here in the rock 'n roll wastelands of south FL which means that, in addition to buying an amp unplayed, it'd cost another $100 in shipping just to spin the wheel of fortune.
This one showed up on Craigslist and, in addition to the 7591s, I got reverb and a 15" speaker for an hour's drive up the coast to Fort Pierce. I also lucked out in that, right after I got it here, a dual Univox footswitch showed on eBay so it's got all its pieces and parts and, although you can't really tell by the pics so far, it's in pretty good condtion ... be nice if it sounds good too. I've had it running and it passes a signal; needs a reverb pot, both reverb tubes, and the unavoidable power supply and cathode caps; all the parts here, no biggie but but but but but.....
May have been played by Elvis!!
That's right folks! Tom Petty was born in N. FL in 1950; was 17 or 18 about when this amp was manufactured. Somebody ... maybe Petty-Daddy ... used one of those electric etching pencils to inscribe the name 'Petty' into the back chassis panel. The seller told me that the guy he bought it from told him that the amp had been Tom Petty's.
Being a Guilder, I discounted the claim but, at some point, I'll probably see if I can contact him ... who knows, if it was his, he might like it back ... In the meantime, I'll have something cleaner and brighter for the Rickenbacker to work with; ok w/ the Gibsons at low volume but when pushed ... the Rickenbacker bite gets lost in the Gibsons' distortion ... it sort of mushes out... so ... we'll see ... anyone got Tom's name in their address book? :lol: CJ