I just finished replacement of the electrolytic capacitors in one of my two (yes, two) Yamaha M-85 amplifiers. Installed a fine bunch of Nichicon KYB, Muse, and Fine Gold. During this procedure I also removed the dreaded Sony bonding glue. I also replaced a zener (D119) which appeared questionable due to possible corrosion from the glue.
At final inspection, I was pleased with the capacitor solder joints. I was not so happy with the D119 solder joints, but they refused to look much prettier after a few attempts at touch-up. In hindsight (always 20/20), I should have desoldered completely, cleaned, and soldered fresh. But I didn't.
I connected the M85 with master volumes set at minimum. I powered up. All was good, and I heard the speaker relay click as expected. I then increased masters slightly and heard good music. Followed by a crackle. Followed by a puff of smoke. I immediately powered down - and I think I heard (hope I did) music still coming from both channels as power was switched off.
It appears R125 may have baked. That is the area served by the zener D119.
While I can solder quite well and have successfully completed a number of high-parts-count kits, I am not a techie with troubleshooting skills.
I welcome any and all input on the matter of how I might determine what other parts may have been damaged and how I may reasonably easily diagnose. Bear in mind I have my second M85, untouched, and fully operational to compare against. I do also have a variac and nice DMM.
I have done some searching and found some posts that might suggest R125 gave up the ghost and saved other components. But I don't know.
Help?
At final inspection, I was pleased with the capacitor solder joints. I was not so happy with the D119 solder joints, but they refused to look much prettier after a few attempts at touch-up. In hindsight (always 20/20), I should have desoldered completely, cleaned, and soldered fresh. But I didn't.
I connected the M85 with master volumes set at minimum. I powered up. All was good, and I heard the speaker relay click as expected. I then increased masters slightly and heard good music. Followed by a crackle. Followed by a puff of smoke. I immediately powered down - and I think I heard (hope I did) music still coming from both channels as power was switched off.
It appears R125 may have baked. That is the area served by the zener D119.
While I can solder quite well and have successfully completed a number of high-parts-count kits, I am not a techie with troubleshooting skills.
I welcome any and all input on the matter of how I might determine what other parts may have been damaged and how I may reasonably easily diagnose. Bear in mind I have my second M85, untouched, and fully operational to compare against. I do also have a variac and nice DMM.
I have done some searching and found some posts that might suggest R125 gave up the ghost and saved other components. But I don't know.
Help?
