MC7200 right channel out...

slimpikkins

Super Member
Hello, last night we had a freak April thunderstorm. Lightning hit a pole out side our home and took out our tv, phone and my Mc7200. The amp powers up, both meters jump a little at power up, power guard lights flicker as well. All is the same as before except there is no sound out of the right channel. I switch sources, speaker wires, exchanged left and right interconnects and have narrowed it down to my amp. I have the cover off and looked things over and of course everything looks fine.

There are only two fuses I see; one one the back next to the power cord and one top front right under the cover. Both are fine. Is there any other things I could check or test first before I take this to service. I own a meter and can do basic checks and am not afraid to take the amplifier boards out.
Thanks!
Jim
 
I think you've done everything......

Its most likely down to component failure so I would be off to the tech with it......
 
I pulled the schematic while at lunch. I would suspect an input IC, used for balanced input matching, could easily have taken a hit via the ground path.
 
I pulled the schematic while at lunch. I would suspect an input IC, used for balanced input matching, could easily have taken a hit via the ground path.
Thank you for going through the trouble pulling the schematic. I don't know what I'd be looking for there though. Not sure what an input IC looks like or even what board/s they would be on. I'm careful and pretty good at replacing parts on circuit boards but testing/trouble shooting is something I have to leave to the tech. I don't have the skills or equipment.
Jim
 
IF you have some XLR cables trying using those instead of the RCA input. This way you can see if RCA or XLR input section is bad. If so then use the unaffected one. Of course if the problem persists then it's deeper inside.

Just FFT.

Jimmy
 
I'll look at the schematic when I open the shop tomorrow. Most likely the op amps are Signetec 5532s.and are located in sockets on the input board.
 
I'll look at the schematic when I open the shop tomorrow. Most likely the op amps are Signetec 5532s.and are located in sockets on the input board.
Yes, it has those on the board behind the input sensitivity switch. I tried reversing those two to see if the problem went to the other channel. It did not work. There are several other op amps on the amp boards but I think you were pointing out the ones I reversed. Thanks again!
Jim
 
Well, we took a shot. Lightning does strange things, will take out one part and leave another adjacent part alone.

Time for a tech to take a hands on look.
 
Thanks a lot for your time. Its really a strange problem. It's heading to the shop in a few. I'll post here what the problem is.
Jim
 
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