Mine was bullet proof, taking command of all my 92 dB and up speakers. Very stable, I killed mine through stupidity, not amps fault. Testing "repair I have attempted, some of the pads from Q1 and Q2 vaporized. A few more parts were burnt in this channel than the other one. figuring that out cost a few sets of Q1 and Q2, and I wore the pads out. The other channel fixed great, came right back. We will see.
New R24 and transistor sandwich
Russellc
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^ R24.... that number sounds very familiar...
The problem I have with the 252, specially in SIT form, is that it never sounds loud. even thought it IS playing loud.
IT's a very clean sounding amplifier and it goads into cranking it up. I did this into the 90db/w speakers.
The MOSFET version is more evil, also really nice sounding but lots more power so I put it against the 83db/w speakers. Thank God that protection circuit works.
I suppose the MOSFET version with speakers with greater than 90 db/w is the solution... or limit yourself to baroque chamber music.
BTW, I did try the 252SIT on the Maggies and it blew my mind... it sounded fantastic, just don't play rock and roll or Mahler through that combination.
The problem I have with the 252, specially in SIT form, is that it never sounds loud. even thought it IS playing loud.
IT's a very clean sounding amplifier and it goads into cranking it up. I did this into the 90db/w speakers.
The MOSFET version is more evil, also really nice sounding but lots more power so I put it against the 83db/w speakers. Thank God that protection circuit works.
I suppose the MOSFET version with speakers with greater than 90 db/w is the solution... or limit yourself to baroque chamber music.
BTW, I did try the 252SIT on the Maggies and it blew my mind... it sounded fantastic, just don't play rock and roll or Mahler through that combination.
Repair went not bad, now to check continuity from each of the legs of Q1 and Q2 to where traces did exist and hopefully good to next connection.
I have noted on this pic of the schematic. If continuity, great, if not I left the legs long on back side for attaching some 22 gauge solid core for repair.
Most of the locations have at least one pad on one side or the other, a few have both, one has lost pads on both sides. I let a small amount of solder go down the leg into the leg hole. Once continuity is established, hook up the variac and bang it!
I have noted on this pic of the schematic. If continuity, great, if not I left the legs long on back side for attaching some 22 gauge solid core for repair.
Most of the locations have at least one pad on one side or the other, a few have both, one has lost pads on both sides. I let a small amount of solder go down the leg into the leg hole. Once continuity is established, hook up the variac and bang it!
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Hmm... in a previous iteration.... see the smoke trail on the board?
I can't complain, we're part of the R&D. And it was fun, didn't burn the house down...
OH NO! Now ZM will be mad at me, and every body will warn me "don't burn this one!! "
Now you know why I don't want to build big amps... little ones that I can run way from.. OK... big ones that might immolate me.
BTW, I was playing Offenbach's Can Can when that damage occurred. Don't play exuberant French music, that's my story. I just couldn't help it.
https://www.google.com/search?q=can...ate=ive&vld=cid:6f5ff1ea,vid:4Diu2N8TGKA,st:0
As you can understand, with that exhuberance, i cranked it to onze.... tout devrait bien se passer, non ?
You know, if you're gonna smoke an amp. I can't think of better than this.. perhaps the finale for the 1812 Overture? But this is IMMOLATION at its finest... just as the band finishes.... "Daddy, do you smell smoke?"..... You know, that amp kept playing until the end. Bravo! Good Show!
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My amps failure was totally on me. It never balked and slammed all my speaks unmercifully. Then I sent a giant transient, through 62 dB phono pre, to pre to unsuspecting xa 252.... unfortunately the preamp was set to "phono" no less. Boneheaded move on my part....
