• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Yamaha "M" series and glue

avionic

avionic

" Black Knights " F-15 back shop EW avionics
Subscriber
Currently have a M-85 in for repair. Symptom : Low distorted volume on one channel.
Cause: Open signal path between the collector of TR113 and the base of TR123 via a 47 ohm resistor.The above board resistor leads were coated with dried up " Sony bond" ie, glue and had corroded the leads off the resistor.This particular amp had IMO 10 times more glue than required to do the job.Thus there was alot of corroded parts.Mostly resistor leads,jumper wires and DC bus strip.Took a little time to chip and scrap all the glue from around all the surrounding components.Replaced all the resistors,jumper wires and a couple zener diodes that were affected.Removed the copper bus bars and gave them a good scotchbrite treatment.
 

Attachments

  • DSC03203.JPG
    DSC03203.JPG
    109.5 KB · Views: 605
  • M-85 glue.JPG
    M-85 glue.JPG
    29.6 KB · Views: 528
Last edited:
Register to hide this ad
I had some "excess" glue in my Luxman. It made some of the resistors look burnt. Does acetone work on this kind of glue?
 
ryuuoh said:
I had some "excess" glue in my Luxman. It made some of the resistors look burnt. Does acetone work on this kind of glue?
Click to expand...

Not sure.I would imagine it would at least "soften up the glue" ..I used some "make up " fluid that softened it up and made for real easy removal.
 

Attachments

  • 5605G.jpg
    5605G.jpg
    42.8 KB · Views: 250
Have gone through this with four M-80, two A-1000, three C-80, one C-85, etc.

M-80's generally need about 10-12 resistors, 2 zeners, those caps you see, couple jumper wires, bus bars cleaned up, and that big 3.9K 3W resistor replaced.

DSC_6005.JPG
DSC_6006.JPG
DSC_6008.JPG
DSC_6102.JPG


A-1000

DSC_6090.JPG


C-80

DSC_9166.JPG
DSC_5987.JPG
DSC_5988.JPG
 
Last edited:
That M-80 looks real similar .. Red line points to the fouled up resistor that was causing the issues in this M-85..
 

Attachments

  • DSC_6006.jpg
    DSC_6006.jpg
    87.9 KB · Views: 446
Really? That's one of the transistors that has a resistor tied to its leg. They really overdid it with the glue on that one! Those are normally out of the blast radius on the M-80's.
 
ryuuoh said:
I had some "excess" glue in my Luxman. It made some of the resistors look burnt. Does acetone work on this kind of glue?
Click to expand...

If the glue is still somewhat flexible, acetone will help soften it. If it's really aged and brittle it may only help loosen its grip on the PCB.
 
brutal said:
Really? That's one of the transistors that has a resistor tied to its leg. They really overdid it with the glue on that one! Those are normally out of the blast radius on the M-80's.
Click to expand...

Yeah..the glue was all over those TO-126 transistors..Made them look like a blackened crusty moss was growing on them..:D
 
Last edited:
As amazing as all that stuff is new from the factory, it's even more amazing that people can get in there and fix things up.
 
yipes!

Mine is over at my friend Franks right now... 2 blown outputs on the right channel and a few other items found already. Waiting on the SM. Where do you source your outputs from? MCM cross ref. shows replacements as 2SC3858/2SA1494 while Sanken shows the replacement is 2 SC 3857.
 
Nice glue horror gallery guys~

@jeffe:
I have used ONsemi devices from Mouser or Digikey for my repairs.
 
jeffe said:
yipes!

Mine is over at my friend Franks right now... 2 blown outputs on the right channel and a few other items found already. Waiting on the SM. Where do you source your outputs from? MCM cross ref. shows replacements as 2SC3858/2SA1494 while Sanken shows the replacement is 2 SC 3857.
Click to expand...

Bdent has those 2SC3858/2SA1494 Sankin subs for around $5 each. I never trusted MCM's supply, seen many stories of counterfeit from them.

These Sankins are tough as nails. I replaced the mica/thermal grease with silpads on one amp and 2 of the outputs burned right through the silpads and shorted collector to ground, lifted a trace, but the outputs are still good. That's the last time I use silpads on anything but plastic cased trans. I just ordered 100 MT-200 mica insulators from fleabay.

On another amp, I managed to solder bridge one of the pre-drive trans to where it blew all four power supply fuses, but not one output was damaged. Fixed the fubar I made and she's singing again.
 
All the japanese units use this construction technique.To include SONY..
I've seen similar issues with Sansui,SONY,Pioneer, as well as others. Doesn't matter what its in , if I see it ,I irradicate it.
 
Last edited:
Just cleaned up a M-60 yesterday. It was not bad, and no damage had been done yet, but this glue has to be removed if you want these beasts to survive.
 
Last edited:
Avionic -- the Terminator

avionic said:
All the japanese units use this construction technique.To include SONY..
I've seen similar issues with Sansui,SONY,Pioneer, as well as others. Doesn't matter what its in , if I see it ,I irradicate it.
Click to expand...

The Terminator blows away the glue :yes:
 
avionic said:
All the japanese units use this construction technique.To include SONY..
I've seen similar issues with Sansui,SONY,Pioneer, as well as others. Doesn't matter what its in , if I see it ,I irradicate it.
Click to expand...

Sony Bond must have come late 70's, early 80's.

I just recapped a Pioneer SX-1500TD for a friend and there was glue, but it's less opaque and still very pliable. The SX-1500TD ran as TOTL, I believe, 1968-1971. I haven't found a reliable source.
 
You must log in or register to reply here.
Back
Top Bottom