concert poweramp...........

[matthias]

Hey Folks,
Can anyone tell me if the concert slave is the poweramp used in the concert lead or bass amps?
Seems my reforming didn't work and now I'm out 3 of the of the 5 power transistors.
Also, how important is it to match these, seeing as they are all transformer coupled?
If Important, where can I source a matched set of 3055's?
also, where can I source the big ol' single unit can caps so I can use the existing mounting rings?
every thing else "looks" good but I have yet to remove and measure all remaining components.

LETS HERE IT FOR SUNN FOR USING SOCKETS FOR THE POWER TRANSISTORS!
-Matthias

[JoeArthur]

The concert slave is the same poweramp as used in the concert lead/bass - year for year.

Reforming?

If you have an electronics place by you they could probably match up a set of 2N3055s... for a price, and if you tell them what to match.

Personally I wouldn't bother.  2N3055s are plenty cheap since they've been considered obsolete for several decades.  Still one of the best power transistor out there IMHO.

You could upgrade.  Just cross-reference them to your favorite xsistor manufacturer.  I wouldn't do this either unless I had a strong desire to pay more.

Check Mouser for caps.  A new mounting kit isn't that much.  You can go over capacity but make sure you don't go under voltage.

[matthias]

Thanks Joe,
By reforming I meant the Filter Caps. they were close to shot, putt putting and all.
My feeble attempt was just that, I believe.
On actual power up I heard them cooking (transistors) a faint ping and popping, almost a sizzle.
a funny smell when I got got my nose up on the vents (after powering down) feeling the the dust covers I felt the heat.
A huge mighty "aw shucks" bellowed forth and I pulled and tested the transistors..........
thats where you came in.
So, after the other components check out, do you suggest to just pick up a dozen or so and try 'em out?
-matthias

[JoeArthur]

Well, you could. 

I would buy 5 and stick them in.  Transistors have such a wide parameter spread matching would be a waste of time, and if you are just going to judge them by ear - why bother.  Your ear (as well as mine and 99.999% of people on this planet) won't be able to tell any difference.  Perfect matching is only good for Hi-Fi anyways and a Concert ain't a piece of Hi-Fi equipment - it is meant to produce a sound, not to reproduce a previously produced sound perfectly.

I said 5 because if I have to replace one, I replace them all.  New micas and grease as well.  The 5th is the transformer primary driver operating in class A, but you already knew that.

Replace them only after replacing the other components, like caps.  Otherwise you could wipe them out and wind up replacing them again.  Lucky they is cheap!!

And give the amp a good dusting out because dust accumulations after years can get to be real foul smelling if not downright conductive.  Check the thermal cutout also - clean it and re-grease.  If you don't solder the lug connections between everything, give them a real good cleaning and re-tension the connections.

Good luck!!

[matthias]

Hey, thanks again Joe!
I hope to go through this tommorow.

  The 5th is the transformer primary driver operating in class A, but you already knew that.

Not exactly, Well I wasn't sure but now I have a more concrete answer.
-matthias

[matthias]

New caps, new 3055's.
Everything else checked out.
It's doing it's thing, so far.
still on the light bulb limiter.
Practice tonight so I'll really put it through its paces.
thanks for the help.
-Matthias