Yamaha M-2 R channel out trouble - help needed PLEASE!! ** Update - Success!
Hey guys, I could really use some extra help on this one.
I have an M-2 with the R channel out.
Question for the gurus; Can I leave the final output transistors out of circuit and test anything so I'm not blowing $20 worth of parts while troubleshooting?
After going through it initially, I ordered enough output devices (on-semi MJ15001/MJ15002) per another suggested thread as replacements for the SA1051/SC2461 (TR509-TR514). Ordered SA1837/SC4793 pairs as replacements for the SA968/SC2238 pairs (TR508/TR507).
It had also dropped TR501, an SA914 so I got some SA1142's (had some SA914/SC1953 pairs, lost them) Everything else seemed (haha) in order. All parts came from Mouser.
I also found a few of the VD1212 (MV12) varistors (D505) and replaced them with series 4148's as a matter of course. There were 2 on the pre-drive board, one on the driver board.
I installed the new new devices, and POOF! Not only did it take out almost all the outputs and TR508 again, but it popped the AC fuse this time. WTF? Although I may have cracked the fuse glass on the bench, who knows.
I went through the amp board a little better this time, pulling all the fusistors and all but one of them (FR503) are open. Not sure if they were the first time around - if I didn't check well enough - I pulled them from the circuit this time to check...
I've checked all the caps parallel to these and they seem OK. I intend to replace all these fusistors now with flameproof resistors of the same value and sufficient wattage and replace TR508 again.
Again, my question is this; can I leave the outputs out of circuit and test anything so I'm not blowing $20 worth of parts while troubleshooting?
Any help with answer, or any other suggestions on this amp are greatly appreciated.
[ edit ] I don't know why this post lost the attachment, but I've re-uploaded it.
Service Manual
Cheers!
Hey guys, I could really use some extra help on this one.
I have an M-2 with the R channel out.
Question for the gurus; Can I leave the final output transistors out of circuit and test anything so I'm not blowing $20 worth of parts while troubleshooting?
After going through it initially, I ordered enough output devices (on-semi MJ15001/MJ15002) per another suggested thread as replacements for the SA1051/SC2461 (TR509-TR514). Ordered SA1837/SC4793 pairs as replacements for the SA968/SC2238 pairs (TR508/TR507).
It had also dropped TR501, an SA914 so I got some SA1142's (had some SA914/SC1953 pairs, lost them) Everything else seemed (haha) in order. All parts came from Mouser.
I also found a few of the VD1212 (MV12) varistors (D505) and replaced them with series 4148's as a matter of course. There were 2 on the pre-drive board, one on the driver board.
I installed the new new devices, and POOF! Not only did it take out almost all the outputs and TR508 again, but it popped the AC fuse this time. WTF? Although I may have cracked the fuse glass on the bench, who knows.
I went through the amp board a little better this time, pulling all the fusistors and all but one of them (FR503) are open. Not sure if they were the first time around - if I didn't check well enough - I pulled them from the circuit this time to check...
I've checked all the caps parallel to these and they seem OK. I intend to replace all these fusistors now with flameproof resistors of the same value and sufficient wattage and replace TR508 again.
Again, my question is this; can I leave the outputs out of circuit and test anything so I'm not blowing $20 worth of parts while troubleshooting?
Any help with answer, or any other suggestions on this amp are greatly appreciated.
[ edit ] I don't know why this post lost the attachment, but I've re-uploaded it.
Service Manual
Cheers!
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