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M-80 Restore

I am about to start on my second M-80. It's serial number is 1836 and it has not had the TSB 66H applied. I'm pretty sure I can figure it out from the TSB, but does anyone happen to have any pics of the TSBs applied?
 
Asmodeus2112 said:
I purchased the 33000µF caps with the stud that are referenced on other threads here about M-80s. Cut the stud off. Also note that one of the caps listed has high screw terminals but the other has low. Space was very tight, but it fit. I was nervous about the stud contacting the chassis back panel. The stud is a negative terminal and on one of the caps will be -88V. I put a big square of Formex as an insulator on the back wall.

View attachment 2350748
View attachment 2350749View attachment 2350750View attachment 2350751
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Very nice work! What did you use to connect the main cap screw terminals to the power supply board?
 
Arc deTriamp said:
Very nice work! What did you use to connect the main cap screw terminals to the power supply board?
Click to expand...
Thanks. I used ring terminals that I bent 90 degree. On the cable side of the terminal I flattened the round crush tube and trimmed the sides so it was like a spade. That part is what went through the slots on the power supply board and was soldered.
 
My second M-80 needs the TSB applied. Working on the parts list. I am pretty certain that the resistors are 1/4W Fire Proof Carbon Film. But I am less certain about the capacitors. I am referencing the M-80 schematic that has the TSB marked up, it is linked to the main M-80 thread. It calls out capacitor types by the marks, so that is what I am going by. But I also noticed that the part numbers on the TSB have prefixes that coordinate with different types of capacitors on the SM parts list. I'm not sure which one to abide by.
upload_2021-12-13_21-53-42.png

Remarks on the schematic:
upload_2021-12-13_21-54-28.png

Anyone applied this TSB to an M-80? Can u help?
 
Mylar is a registered trade name for polyester film..

Polystyrene is not part of the TSB use polyester ( Mylar )

FE Mica -- silver mica ---> $
 
My other M-80 (Serial # 11454) does have the TSB. I'm going to pull it out of service and use it as reference to see how the TSB was applied there.
 
Of the changes listed on the TSB:

R151/R152 100 Ohm to 220 Ohm = I see that, no problem
C301-C304 .01 mf to .022 mf = I see those, no problem
R347-R350 33 Ohm = ? See #1 below
C347-C350 .01 mf/50V = ? No clue, but got stuck with R347-R350 so have not researched too much
C159-C160 = I see where those go, they are unpopulated on the PCB, so just populate them with the right caps.

#1 So, I pulled my newer M-80 that has had the TSB applied prior to my ownership. And the resistors on the TR's legs are 47 Ohm, not 33 Ohm as called out in the TSB. o_O

Also on the M-80 schematic with TSB's highlighted in red that is linked to some of the M-80 threads here, the R347-350 are shown on collector of TR 119 and emitter of TR125. And the TSB shows adding the C347-C350 caps in parallel? :confused:
upload_2021-12-21_21-56-58.png

But on my reference TSB'd amp there are 47 Ohm resistors installed on the legs of TR 117, 123. I also cannot find C347-C350 on the reference amp. I see that on the M-85 schematic there are 47 Ohm resistors R241/243 on the base of TR 117 and 123.
upload_2021-12-21_21-59-35.png

I will keep plugging away to try to understand what is going on, but some insight would sure be welcome.
 
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