Update and upgrade Peavey Century

[phydauex]

Howdy All,

First off, I've been coming here for info for awhile and decided to get on board.  Thanks to everyone in the past for the great advice & insights.

My current project in front of me is an older Peavey Centry (200 series),  that I've worked on before had a couple blown output devices (original RCA 62792)  with weird noise and shorting problems.  Turned out to be broken leads on the driver transformer, and several burned resistors that i think fried when the trans shorted. 

Got that dealt with and replaced the blown outputs.  Six months later, it's back with 2 more blown outputs, one on each side of the transformer.  One of them was another old one and one of the new ones I replaced (2n3055 from RatShack).  With those out the amp turns on and plays ok with the remaining two outputs, albeit at half power.  I know I probably should have replaced all four, but I didn't, lesson learned.

I said all that to say I'd like to use a more reliable higher rated transistor than the  2n3055, and I know from digging that there are options.  From a design standpoint, should I look for something that has a higher voltage rating (MJ15015), but simiilar current & HFE ratings, OR  a device that has higher specs in every catagory (ie MJ15001, MJ15003)? 
I want this to be more reliable for the player and not have it back every 6 months to replace the outputs.  As far as I can tell nothing else looks out of place voltage wise, and I'm chaulking this up to marginal parts.

Any thoughts, suggestions?
Sorry, I can't seem to find the schematic on line.  I have a paper copy in front of me***

[phydauex]

Just looking at it again and one pair of outputs is running 67v on the collector.  This is supposed to be a 60v device, maybe a little too close for comfort?

Popped in a couple replacements , seems stable, not lighting up my bulb limiter at all.

Still has the original giant cap in power supply (3500uf/80v).  I have no idea what kind of life span those computer grade caps have, seems to filter the b+ pretty good, little ripple.

Matt

[J M Fahey]

Use the beefiest you can find.
Enzo usually suggests MJ15024.
Replace all 4 and sleep like a baby.
You can scan the schematic, either at home, or school or cybercafe and post it here.
Check that the small print stays readable..
Schematics are always welcome.

[Enzo]

I like the MJ15024, but certainly the MJ15003 is more than enough transistor here as well.   I see no problem with the MJ15015,either, but I don't happen to stock them.  I do stock the others, they are common in amps, or were.  OEMs are getting away from TO3 trasnsistors these days.

[phydauex]

Thanks,  I have a set of MJ15003's on order.  Good to have a resource to ask questions of, while I figure this stuff out.
Matt