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Odd M60 Problem

UPDATE:

I got my order so replaced the rest of the zeners, brought it up and no dice.
Taking voltage measurements I found that a lot of the points had higher than the high rail voltage so I checked the schematic and found the HB+/- is 60v.
Why not desolder the leads (there's a two pin connector going in by the Auto A stuff) and see what happens?
I powered it up on the DBT and it came out of protection. I jumped when relay closed because I thought something had popped, ha.

So, with the HB leads disconnected the amp is powered up and out of protection. Now I just need to see what the heck is shorted causing the HB+ voltage to go all over the place.
 
Still pretty stumped with this one.
I have pulled to check and/or replaced every single device on the bad channel and also compared visually with another M60 and I still have no clue what can be wrong. I figured I may have put a transistor or diode in backward but as far as I can see everything is as it should be.

Basically it's got 60v running all over the place including to the input of the speaker relay if the small two pin HB+/- lead (right behind the two 1000uf caps) is soldered in. If I disconnect this it comes out of protection and my voltages are sane and somewhat close to where they should be (obviously will be off as it's missing the outputs and is on a DBT).
If anyone has any idea what in the world could be wrong/where to poke next I'm all ears. I won't be able to get back to it for a few days but I'm definitely open to suggestions.
 
APS transistors (TR147-149 and TR155-157) are ON or OFF? They should be in OFF state.
 
I had some time to get a few measurements tonight and here's what I came up with

TR147-149 I have E 54v, B 55v, C 55v
TR 155-157 I have E -32v B 55v C -31v
TR159 ECB 55v
TR 161 E 44v C 0v B 53v

TR159 and 161 have been replaced so should be good. The old ones also tested good. The 12V zener D133 has been replaced, old one also tested good. It has 54v at one end and 44v across.
As I said before I've replaced or checked every single device on this channel. Now I've even gone so far as to pull most resistors and check them just to be sure none of them are open.
Also, as I mentioned before it will happily come out of protection if I pull the small HB+\- leads off the board and all the voltages are more or less correct.

I'll edit to add that:

TR 127 ECB ~50v
TR 129 E 51v, C 16, B 51v
TR139 ECB ~50v
TR141 ECB ~50v
TR143 ECB ~50v
TR145 B 55v, C -8v, E 55v (good according to schematic)


Ideas?
 
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I'll look tonight. I believe they've all been changed.

I will check voltages across these diodes and their corresponding diodes on the other channels and maybe I can find where the problem pops up.
 
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I ran out of troubleshooting ideas so jumped in and went point to point comparing resistance from the good half to the bad half and found R117 and R119 to be showing 1k rather than 220ohm as the good side and the manual called for.
I pulled them and they were 1k fusistors where the good side had 220ohm fusistors. I replaced them with 220 ohm flameproof and it popped right out of protection. Showing around 3mV of offset on the repaired amp.
So, um, I guess I fixed it. This thing had obvious work done before and all of the replacement parts were the same numbers and most likely factory stuff so maybe it was just a really poor job done by a Yamaha service center?
I'm still not exactly sure why the added resistance would cause those crazy voltages I had all over the place. I mean the thing must have run after having them installed? I really have no clue.
 
That's awesome you got it going again!
Were the markings on them consistent with 1k as well?

Great news anyway. Tried her out yet?
 
Yeah, the resistors read 1k on the bands and on my meter. I actually checked them before but called them good because of that. I only noticed they were incorrect when comparing to the other channel and then the service manual.
It makes me feel slightly better that it took me so damn long to figure out what what wrong because that was something that I'd never normally consider. Oh well. I'm just glad it's running.

I haven't tried it yet. I've still got to replace the micas and paste, replace the protection relay, recap and put in some Bournes trimmers before this parts amp resurrection is complete. I am guessing I should also replace replace the small signal transistors in the other channel to match the repaired channel?
 
Well. It sounds promising. Keep plugging away at it.
OMGCat! said:
I am guessing I should also replace replace the small signal transistors in the other channel to match the repaired channel?
Click to expand...
I wouldn't think that would be necessary.
 
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