Help reviving M-80
- Thread starter RayN
- Start date
+45 and - 45 vdc?
Check the 33Ω resistors circled in red as well as the 220Ω circled in red.
http://sportsbil.com/yamaha/m-80-s-with TSB66H.pdf
The 33Ω resistors are on the narrow strip, APS circuit boards up topside.
http://sportsbil.com/yamaha/m-80-s-with TSB66H.pdf
The 33Ω resistors are on the narrow strip, APS circuit boards up topside.
How are you testing these?
In circuit or out?
RayN
Active Member
OK, thanks, I'll have to track these resistors down. I really appreciate your help!
The only thing you have to remember is it is the front pair of emitter resistors for each channel. M-60/65/80/85. That photo I posted earlier was and M-65.
Hoping you get this baby going again.
RayN
Active Member
Did some sleuthing this morning. I found 2 33ohm and 1 220ohm resistors on each of the two transistor connector boards on the top. Are those the ones in question? One of the 33ohm guys is open, the rest test out fine. I also went through all the vertically installed resistors on all boards and, while I didn't necessarily test for value, none are shorted or open (I tested in circuit). It makes sense that the failed transistor in the left channel and the failed resistor in the right may be what I'm dealing with.
RayN
Active Member
Me too! It looks a bit sad like this.
Attachments
RayN
Active Member
Found one more casualty, it's one of the transistors on the main board with a resistor attached to the base. The resistor is good but the transistor is completely shorted. This is marked A1352 which is a PNP. Can I replace this with a higher rated PNP transistor, such as a MJE15033G (I have those in stock)? I assume not, but I thought I'd ask.
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Those TO-220 would be a pain in the ass. Twisting leads around and way overkill.
These are easier to deal with...
https://www.mouser.com/datasheet/2/308/KSA1381-1301132.pdf
B+D Enterprise may even have the real thing 2SA1352.
