fender frontman 212 distorted output

[pontiacpete]

Haven't replaced Q9 or 10,
Is there a good sub I can use, I have lots of transistors but no 2362s I believe
but looking

[Jazz P Bass]

For whatever reason, they used a high voltage part.
120V C to B.
The pinout is E C B looking at the flat face.

http://81.233.9.161:800/_pdf/2SA/2SA1016.PDF

[pontiacpete]

Could I get away with a low voltage sub?

[Jazz P Bass]

To try?
Certainly.
It's working off of a +42 volt rail.
Keep in mind the tail is ultimately connected to the -42 v rail.

[pontiacpete]

I once rebuilt a polytone and used two 2N5210s in a similar application, a sub for Q1 an obsolete part PT1583
Will those work here?

[olddawg]

I'm back to working on this amp. Fortunately it does not belong to a customer. After changing out U6 and the amp worked I put it under my bench with plan to post it for sale and finally get rid of it. Then one of my customers comes by I take it out to demonstrate it's wonderful sound and it's back to sounding like it hell. So I put it back under the bench with the hope of returning to it.
The weird thing now is that I'm finding that if I touch my probe on one of the leads of the diodes in the string D21-23 the amp works correctly, distortion gone.
If i randomly probe components around the area the distortion comes back and the bottom half of the wave goes askew. Can't seem to be able to do this on command but I can correct the problem by touching one of the diodes.
Any one want to take a stab at this.

Have you tried tickling components in that area with a can of freeze mist and/or a heat gun?

[g1]

The weird thing now is that I'm finding that if I touch my probe on one of the leads of the diodes in the string D21-23 the amp works correctly, distortion gone.
If i randomly probe components around the area the distortion comes back and the bottom half of the wave goes askew.

Maybe there is an oscillation that the probe placement is "curing" ?

[pontiacpete]

havent' tried the freeze yet

I was thinking there might be an oscillation, also

[bobloblaws]

havent' tried the freeze yet

I was thinking there might be an oscillation, also

Hi Pete, did you ever get this resolved? I'm having almost the identical problem with my FM 212. It works OK most of the time but randomly makes a crackly sound when it feels like it and goes into a distorted output state from time to time. I have the exact same experience where I can "fix" it (until it does it again some time later) by touching touching my probe to D21 or in that vicinity. I started a new thread earlier today for it.

[pontiacpete]

I'm sorry to say that I haven't yet figured this one out. I have the chassis sitting at the end of my bench vertically for the longest time. I've been following a recent thread about this amp with the hope that I'm might get some insight as to the problem.
Yes, it was weird that it would work fine until touching a probe around in that same vicinity. But now I"m getting very little sound out of it.
I was tracing a signal the other day and found that I could see a signal into the power amp but haven't gotten much further.
I hope you can find something to help me out.

[bobloblaws]

I'm sorry to say that I haven't yet figured this one out. I have the chassis sitting at the end of my bench vertically for the longest time. I've been following a recent thread about this amp with the hope that I'm might get some insight as to the problem.
Yes, it was weird that it would work fine until touching a probe around in that same vicinity. But now I"m getting very little sound out of it.
I was tracing a signal the other day and found that I could see a signal into the power amp but haven't gotten much further.
I hope you can find something to help me out.

Can you send me a link to the recent thread you mentioned?

[pontiacpete]

here ya go,

https://music-electronics-forum.com/...ad.php?t=49822

[bobloblaws]

here ya go,

https://music-electronics-forum.com/...ad.php?t=49822

Thanks, Pete!