Mysterious brown substance

[Erik S]

Transistor fluid?

This is the inside of a non functional yamaha stereo pre-amp.

These two heat sinked transistors are surrounded by brown gunk

I would have guessed it was capacitor puke, but I can’t spot any culprits.

 

[LukeFRC]

most things turn to fluid at high enough temperature

 

[Erik S]

most things turn to fluid at high enough temperature

Facts.

 

[jwin615]

Old thermal compound would be my suspicion. Or old wrong thermal compound

 

[Harry Klippton]

Old thermal compound would be my suspicion. Or old wrong thermal compound

Came here to say this

 

[Erik S]

Old thermal compound would be my suspicion. Or old wrong thermal compound

Maybe.

The transistors unexpectedly both tested okay on my tc1. And the compound joining them to the heat sinks looks okay.


The goop ate a resistor, so I’m gonna throw a couple resistors in it and see what happens.

 

[spi]

The mojo spilled out

 

[Erik S]

It lives!

Still no idea what the gunk was, but it’s making sound now which I’m excited about.

 

[ICTRock]

should have been replaced with flameproof resistors of a higher wattage rating with an air gap between the resistor and the board

 

[Erik S]

should have been replaced with flameproof resistors of a higher wattage rating with an air gap between the resistor and the board

Maybe. But for now 1/4w tayda blues are going to have to do.

 

[music6000]

A great result considering it looked beyond repair, just some surface rust!

 

[Nostradoomus]

 

[derevaun]

Looks like a party I’d have liked to been at

 

[Erik S]

Looking back at this a day later, I think it was glue. There’s some tell tale stringing in the first pic.

I replaced some caps on a crate amp a while back that were glued to the pcb, and I googled what kind of glue I should use for the repair. There was something about some kind of glue or silicone that might become corrosive over time.

Those big heat sinks are pretty wiggly just supported by the transistor pins, so it would make sense to tack them down with some glue.

 

[darwin999]

Looking back at this a day later, I think it was glue.

Agreed, that's what it looks like to me, too.
But you should win some sort of prize for this thread's title.
"Mysterious brown substance" gave me a laugh!

 

[Erik S]

you should win some sort of prize

I accept.