Power Transistors

[Pure_Brew]

I think the PS Audio I have uses the same devices as the big PL's. Those hard to come by these days? Seems discontinued and I see working pulls out there. Are you substituting?

 

[laatsch55]

Yes and have been. What's the numbers Joe?

 

[Pure_Brew]

Amp is at work at the moment 555/600 I think , can't remember the letters off hand. Built by NEC

 

[laatsch55]

Yep, 2SD555's, 2SB600's. Complimentary pairs froma lot of amps in the 70's and 80's , very reliable, well built.

 

[Pure_Brew]

What do you substitute with?

 

[laatsch55]

MJ21195, MJ21196

 

[Pure_Brew]

Good to know. Unfortunately, while the amp still has its merits, one of the main boards has a hot spot on it. Likely that will be the end of it at some point. One of the traces lifted right off before I got it. It has since been reinforced. There are no replacement boards.

 

[laatsch55]

Can you take a pic of the board??

 

[Pure_Brew]

I will when I bring the amp home.

 

[laatsch55]

Cool.

 

[Pure_Brew]

Not a PL, but is there a WO possibility for something like this????

 

[laatsch55]

Ya mean a board replacement?

 

[Pure_Brew]

Yeah I think so.

Maybe.

I really think based on the history of these, the boards could not deal with the heat coming off one of the devices (not the power transistors, maybe some sort of regulator). This would require some kind of modification, or maybe a daughter board at the very least
[attachment=0:3hvws9xf]Other PS Audio 200c(x).jpg[/attachment:3hvws9xf]
This is not my amp but similar. I still have to bring mine home.
It's kind of interesting the way the output devices are using the buss bars for ground (and heat!), and the rest of the buss bars drop down and go across the caps.

The damage on my amp would be on the flip side of one of the boards.

 

[laatsch55]

Joe can draw up a board in a hurry, especially if he has an example to go by. He did one for me on an industrial timer board and I couldn't be happier.

 

[Pure_Brew]

I think he's only like an hour and a half from where I live actually.

 

[Pure_Brew]

I'm likely going to back-burner this in light of other things going on. It's randomly popping and crackling loudly on the right channel after it's been on a bit. It popped loudly on some 901's I was messing with and boy was that loud!