Is it savable?

[petehall347]

that used to be a relay ..
best guess is the amp is shorted at the output . i fear someone has been let loose with a screwdriver in there .
it looks fixable though . new parts needed .

 

[Lets Go Back]

Screwdriver, big hammer or whatever else they thought may work.

 

[elnaldo]

Well I was thinking about starting on the 9090 this weekend and was gathering a list of items that I would have to get from storage, While checking the connecting points of the cut black wire I came across this on the protector circuit board. Any ideas on how to repair this new nightmare.?View attachment 1028731

Just remove that broken relay and get a new one. RL01 in the schematic or service manual. I'd redo the whole protection circuit (new capacitors and transistors)

 

[Ds2000]

What the hell are folks thinking when they do this to a part inside of a unit? I mean that someone couldn’t have thought doing that would help.

 

[elnaldo]

Using my "reverse thinking engineering" I guess the relay didn't engage so somebody decided to hard-wire the contacts. And the problem got worst.

 

[Lets Go Back]

Using my "reverse thinking engineering" I guess the relay didn't engage so somebody decided to hard-wire the contacts. And the problem got worst.

Yes worse for me...Probably started out as needing a couple resistors replaced, now a complete rebuild is what I may have to do.

 

[Lets Go Back]

So getting back to the 9090db I have been slowly recapping and rebuilding the unit. Including repair of the bad traces and cut wires I found totally shattered diodes, toasted resistors and today I tested the output transistors and all seem to be bad as well. My question is what is available replacement for these. Looks like these are available on mouser, MJ15025G, MJ15024G. Thanks for the reply and help.

 

[OMGCat!]

Good job on spending the time to get it back into shape again. I've had a few projects that "weren't worth fixing" that I spent a bunch of time on. I had fun and learned a lot which was more than worth it to me. Getting a great vintage unit back up and running was just a bonus.

I'd do a search for '9090DB output transistors audiokarma' in google and see what pops up. I believe those MJs are the go to replacements for nearly everything these days needing TO-3s.

 

[Lets Go Back]

Thanks for comment I will be ordering today.

 

[larryderouin]

Although the Mj21194G and MJ21195G look like mirrored pairs, they actually aren't. Correct pairing is MJ21193G with MJ21194G, OR MJ21195G with MJ21196G. The spec's are virtually identical, but to be safe use the correct pairing.

 

[Lets Go Back]

Although the Mj21194G and MJ21195G look like mirrored pairs, they actually aren't. Correct pairing is MJ21193G with MJ21194G, OR MJ21195G with MJ21196G. The spec's are virtually identical, but to be safe use the correct pairing.

Thanks for the heads up, appreciate the info.