Looking at a Yamaha M-80 today.

[avionic]

I opened up and M-80 a while back. It belonged to the original owner. Expecting to find the usual glue mess. Besides having a rather heavy coating of cigarette tar & nicotine on everything. I'll be damned that this one had no glue. Period.. But it did have a chernobyl'd channel.

 

[blhagstrom]

Don't you love fixin' these

One of MY favorites

Owner is "up" for repair.
Dammit

 

[avionic]

One of MY favorites

Owner is "up" for repair.
Dammit

I know. Been there and done a few myself.

 

[pustelniakr]

I opened up and M-80 a while back. It belonged to the original owner. Expecting to find the usual glue mess. Besides having a rather heavy coating of cigarette tar & nicotine on everything. I'll be damned that this one had no glue. Period.. But it did have a chernobyl'd channel.

Any idea what triggered the melt-down?

I have one awaiting recap and replacement of glue affected coponents, that I had to completely disassemble to get at for de-gluing. I'm a bit ambibalent about putting it back together and powering up. It worked, but would go into protection intermittently. I usually don't recap until I get full function, but ain't no way I'm taking her back apart to recap. Dang the torpedoes! Full speed ahead!

This model doesn't choke on a variac does it?

Enjoy,
Rich P

 

[avionic]

This model doesn't choke on a variac does it?

Shouldn,t. Check/reflow the solder connections on the TO-126 transistors on the main board.(8 total) And the TO-220 transistors hanging upside down on the thin narrow APS boards up top.( 2 per board ).

 

[whitrzac]

Why do the stock output relays have magnets on the side of them?
Do they need to be installed on the new relays?

 

[avionic]

Why do the stock output relays have magnets on the side of them?
Do they need to be installed on the new relays?

No. SWAG -- to deflect the plasma arc away from the contacts and reduce contact pitting.

 

[whitrzac]

New parts are in. Cleaned everything up. Double checked wireing/etc.

It didn't blow up, but it did pop both 10a 250v fuses...

 

[pustelniakr]

Bad news...Chernobyl-scale bad news.

Rich P

 

[avionic]

Bad news...Chernobyl-scale bad news.

Rich P

Well..Shit happens. Roll up your sleaves and start checking components.

 

[avionic]

New parts are in. Cleaned everything up. Double checked wireing/etc.

It didn't blow up, but it did pop both 10a 250v fuses...

Thats not a good thing.

 

[avionic]

New parts are in. Cleaned everything up. Double checked wireing/etc.

It didn't blow up, but it did pop both 10a 250v fuses...

Look for pinched/ chaffed wires around the power transformers.

 

[whitrzac]

On the power/capacitor board. The spot that the 2 black wires(BL-BL) land from the transformers are 0ohm to ground(heatsink) with the transformers disconnected.

 

[avionic]

On the power/capacitor board. The spot that the 2 black wires(BL-BL) land from the transformers are 0ohm to ground(heatsink) with the transformers disconnected.

Thats correct. Black wires are ground wires. Thats why you need insulators on the output transistors.

 

[avionic]

Does your unit have a silver(aluminum) heatsink or a black anodized heatsink. Silver are the multivoltage units. Black are not multivoltage.

 

[whitrzac]

Pulled everything apart again. Didn't find anything obvious....

It's a multi-voltage unit.

All of the insulators were on the outputs transistors. If one wasn't, would that give similar symptoms?

 

[avionic]

It's a multi-voltage unit.

Look for shorted wires around the voltage selector switch.

All of the insulators were on the outputs transistors. If one wasn't, would that give similar symptoms?

Oh yes. Did you check the 4 upper MT-200 rail switching transistors ?

 

[avionic]

Does your unit have the 4 fuses on the E-capacitor board ?

 

[whitrzac]

3 fuses on the power switch board. 1 fuse on the meter board.

 

[whitrzac]

Is there anyplace in the US to get mt-200 insulators?