Hi All,
I posted about an unusual 845 amp here: https://www.diyaudio.com/forums/tubes-valves/358486-re-unusual-845-amp.html
I couldn't get it to not oscillate. I've gutted it since those pics to try the Grover Garland 6sn7-EL34-845 circuit folks have extolled over on AA. I know this is dangerous at my knowledge level. B+ is running about 850V under load. At least I added bleeders!
While I await the Mouser order, anybody have thoughts on what those giant transformers could be? They are about 6x6x4 inches, potted in wax. They fill the bells. No markings. EIGHT leads. I'm thinking red and brown are the primary, and then black, brown, yellow, green as secondaries. Maybe brown is 4 ohm, yellow is 8, and green is 16? And then another winding with black/yellow and brown/yellow ....
I'm curious not only because I'd love a conclusive wiring diagram and the spec'd output impedance, but also because it would be interesting to know where they came from.
Cheers,
Paul
I posted about an unusual 845 amp here: https://www.diyaudio.com/forums/tubes-valves/358486-re-unusual-845-amp.html
I couldn't get it to not oscillate. I've gutted it since those pics to try the Grover Garland 6sn7-EL34-845 circuit folks have extolled over on AA. I know this is dangerous at my knowledge level. B+ is running about 850V under load. At least I added bleeders!
While I await the Mouser order, anybody have thoughts on what those giant transformers could be? They are about 6x6x4 inches, potted in wax. They fill the bells. No markings. EIGHT leads. I'm thinking red and brown are the primary, and then black, brown, yellow, green as secondaries. Maybe brown is 4 ohm, yellow is 8, and green is 16? And then another winding with black/yellow and brown/yellow ....
I'm curious not only because I'd love a conclusive wiring diagram and the spec'd output impedance, but also because it would be interesting to know where they came from.
Cheers,
Paul
Measure windings' DCR. Apply 10 VAC from wall wart to winding with highest resistance, then measure AC voltages across other windings. This will give you the idea of ratios and winding termination. Then measure primary inductance, and you will have a rough idea of what this transformer is.
Yeah--I put a signal on the secondary and calculated to the turns ratio a couple of months ago. But that won't let me figure out which secondary tap is which, will it? And even with all the taps identified, I'd still like to know who made it.
Paul
Paul
Doubt anyone cares, but I think these came from an early Cary 805. They not only look identical on the outside in pics, but some available under-skirt shots show the same secondaries: 4 ohm=yellow, 8 ohm=green, 16 ohm=brown. (Wrong above, which was just a guess. I measured before finding the 805 pictures).
Unless these were available to the DIY market, curious to think about what circumstances would have led one to gut a pair of Cary's in favor of a DIY amp!
Still not sure what the winding is that is neither the primary nor the secondary. (Brown/yellow and black/yellow). Maybe a different primary? The ones I'm using are fairly low impedance (I think around 6750) for an 845 amp, but that is getting me plenty of power (20W) despite a relatively low (900V) B+.
Paul
Unless these were available to the DIY market, curious to think about what circumstances would have led one to gut a pair of Cary's in favor of a DIY amp!
Still not sure what the winding is that is neither the primary nor the secondary. (Brown/yellow and black/yellow). Maybe a different primary? The ones I'm using are fairly low impedance (I think around 6750) for an 845 amp, but that is getting me plenty of power (20W) despite a relatively low (900V) B+.
Paul
Attachments
Cary had a penchant for beating the living guano out of vacuum rectifiers, with excessively large filter capacitors.
There was a sister company selling cary transformers to the diy market. I can't recall the name right now but I seem to remember them selling transformers for transmitter triodes.
Audio Electric Supply? The prices looked decent but I never bought any. The website seems to have been lost to time.
Of the lowest DCIR coil, the highest votlage will be the 16R, root2 or 3/4 of that voltage will be the 8R tap, and half its voltage will be 4R. Maybe a FB coil for the third, or perhaps a CFB coil?
Douglas
Douglas
Close! Audio Electronic Supply
The 805 transformers were expensive but probably reasonable for what they were
Could be another secondary intended to be paralleled with the tapped one. Easy enough to find out, the same method used to calculate nominal primary impedance.
YOS,
Chris
Not the case here--the 805s were/still-are-after-30-years SS rectified. And still a mere 2 feet long per monoblock ....
Paul
I didn't realize they sold OPTs standing alone! Pretty sure this is them based on looks, though the catalog says 5.25x5.25x4 and mine are a solid 6x6x4. But, they also changed the case at some point (later ones appear stamped from one piece as opposed to folded and welded like the early ones/mine), so it is possible they were once a bit bigger. The specs otherwise match up. I can confirm mine are wax potted, same taps, same colors, etc.
This is neat to know! I suppose I have plenty of transformer if I decide I need to drive the 845s into A2 in pursuit of power, either with an IT ala the original or George's powerdrive.
Paul