help with sunn beta lead

[seadflo]

Ive had a sunn beta lead for a while now.
and recently, it suddenly lost all power unless the drive and level is turned all
the way up.
now, it still sounds VERY crunchy and loud, but i really liked it for the clean sound.
and it used to sound VERY loud and clean at 2 on the level with barely any drive.
Anyone have any leads on this.?
While I am by no means a genius in repair, i dont want to ditch this amp or just use it as an oversized distortion box.
I really like the amp.

Local repair says its not worth fixing..meaning..alot of money on their end.

but..
yeah.
any input for my ignorant self would be greatly appreciated..
thanks.

[Enzo]

What do they mean not worth fixing? A basic bench fee should cover at least the diagnostic. They are just being lazy telling you that up front. Did they even consider what might be wrong with it?

Plug a spare cord from send to return on each effects loop. If that helps, then the return jack needs service.

[loudthud]

First step: Try a different speaker to confirm it's the amp.
Second step: Download and print the service manual pages here:

http://sunn.ampage.org/site/svcmans/beta/

Go to ebay and print out the auctions where a beta 2x12 lead recently sold for $400+ and a beta lead head without box got a bid for $300 in the first 2 hours of the listing.

Take everything back to the tech and if they still think it's not worth fixing, find someone else.

[Don Moose]

I sent you an email offering a manual with schematics if you'd find that useful.

In addition to the jumper-past-the-loop connections trick, try each of the send jacks to some other amp's return (or even input). If the preamps aren't good, I'm going to suspect one of the low-voltage power supply connections (or rails). If it's just the power amp ... well, let's hope Enzo can help (again).

In fact, you should probably search on Beta or Solid State and Enzo.

Hope this helps!

[Enzo]

These are pretty conventional amps, my experience is nothing special, it just seems not many around here want to dig into solid state.

[Don Moose]

seems not many around here want to dig into solid state.

Or have the confidence to try to bridge their tube experience to silicon.

[Enzo]

When I train technicians, one thing I try to drum into them is that troubleshooting is troubleshooting. A tube amp blows fuses, what's the first thing to mind on a short list? Output tubes, rectifiers, caps? And yet the same guy facing a SS amp blowing fuses won't consider output transistors, rectifiers, and caps. Output devices, power supply. And in both cases, way down the list - transformers.

Same thing with the signal path. Every stage has an input, an output, and a power supply. Does it matter that much whether the stage is a 12AX7 triode or a 4558 op amp? Signal comes out of it or not. Signal reaches it or not.

[Don Moose]

It's the SS amp's habit of continuing to fry outputs when a driver is toasted - the nearest tube equivalent is a leaky PI coupling cap - and the inconvenience of testing soldered transistors vs. socketed tubes.

... and my impatience.