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M-80 and it works! For now anyway

avionic said:
Sorry but thats not me... I'm only on a couple other forums and hobbymachinist is not one of them.
Tapeheads ,DIYaudio,The carversite, and Phoenix audio. 99.9% of the time here on AK.

I was backshop TEWS for F-15C ,D & E models. 20 yrs.
Click to expand...
That's quite the bird....
 
I've decided to sell this one. Prior to listing I wanted to make sure it sounded good and discovered that the right channel is a bit weak. This one has not had any updates done to it but I did replace C111, 112 with Nichicons based on another thread I found. No difference. This one has very little glue and what was there was easily removed with no apparent damage. Long back story but it's time to start thinning the herd. I'd greatly appreciate any ideas for a hopefully easy fix so I can pass it on to another fan. My original plan was to restore this one since cosmetically it's beautiful and it works. Thanks
 
I'd replace the electrolytic caps on the main board & X-power boards and troubleshoot from there. 34 caps. Most easy solution I can offer. The caps are dead from age, or dying. I wouldn't even turn the power on without replacing them considering the age.
EDIT: meant APS boards vice X-power boards. The 2 little boards on top of the heat sinks close to the top cover. Either way, re-cap the old bitch and it might just work or will find the issue in the process. Look for loose board grounds & bonds while going through it.
 
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I'm in the process of replacing caps and found that C164 has a 100uf 25V black gate installed. Soldering on the board definitely didn't look OE. I'm installing the correct bipolar 47uf 25v piece. Hopefully I get this right channel back up to snuff.
 
There was an article titled " an M-80 that no longer lives up to it's name" awhile back and the gentleman referred to the APS boards as the "X" power supply. That's what I thought they were until you corrected it. I'm sure lots of folks read that one and assumed that to be correct. If not too much trouble, could you point out the difference between APS and X power? Thanks again.
 
APS -- ( power supply board # 4 ) Controls the upper 4 MT-200's.. For high speed rail switching " on demand " transistors. Switching +LB to +HB as well as -LB to -HB when needed.
 
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R221 & R222 might be corroded. C137 & C138 might be corroded too. Plus the little jumpers in between. Check for loose board screws too. One of them will be a chassis ground screw, loose= bad but also= easy fix. Good luck.
 
The weakest & poorest factory soldering I've seen on those is at the diode farm by D113. All those diode solders were cracked on mine. Piss poor soldering was also found at the jumpers adjacent to the big transistors. J229 &J230 for example.
 
This one seems good now. I just ripped out every cap and replaced with Nichicons and went over practically everything that has solder. It was either a cap or maybe a bad solder someplace. It's cosmetically pretty nice and had good binding post mods when I got it. Kinda want to keep it but I've got too much stuff and still have an 80 and an 85 to fix. Step son just bought a beat up MX-1000 but no protection light so hopefully a thorough rebuild keeps it alive. Thanks guys, I appreciate all the help.
 
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