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My Amp is Broken - Not Sure What to Do - Any Recommendations?

I went to turn on my Audio Research SD135 amplifier the other day, but it will not turn on. According to the Audio Research service technician I spoke to, the problem is a broken Thermal Trak module chip. He said that it is a temperature sensing component, and that replacements are no longer being manufactured. He said that it is a known problem, and that Audio Research will give me credit to purchase an Audio Research amplifier from an Audio Research authorized dealer. 

I was wondering if Audio Research makes anything powerful enough to drive Vandersteen 3A Signature speakers (which need between 100 - 200 watts of power)? I am using an Audio Research SP8 Mk II as a pre-amp.

I don't really have much of a budget and am not sure what to do. I would appreciate any advice. Thank you.
distortions

Showing 3 responses by atmasphere

atmasphere's avatar
atmasphere
12,010 posts
 
I would look at the spec sheets of the new and old parts. The things to look for are maximum current, breakdown voltage, hfe. If those three things are right, then its likely no worries.

Obviously there's a little bit of engineering to do all this, but its not rocket science. Any tech (not engineer even) that actually went to school should be able to do it. Matching shouldn't be a huge deal.

If you get it right, the sound won't change. This is mostly a reliability issue. BTW $50/hour sounds cheap!

Regarding reliability of the replacement parts, ARC may have the same concerns as you; if this were my amp I would share that concern!
atmasphere's avatar
atmasphere
12,010 posts
 
Hm, The output section is right out of OnSemi's application notes.

Devices like this give me the willies, since so much relies on them. If it were me, I would be tempted to test the transistor portions to see if they are still good, and if so, perhaps see if a diode applied the transistor could sub for the diode portion of the device. If the amp heats up or has crossover/notch distortion issues, then a bias scheme would have to be employed.
But of course outfitting it with new devices seems the preferred method. This just doesn't seem like it would be that hard to sort out.
atmasphere's avatar
atmasphere
12,010 posts
 
So- the chip can't be bypassed?
If its a fire concern, couldn't a thermal fuse be installed?
*IF* that's all that's wrong, sounds like a simple matter to sort out, if all that is needed is to just get it running again.
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