Hello, I have a C-Audio TR850 old-timer on the bench for a quick tidy-up following a bodged repair by another. After resoldering a detached bus capacitor (the original complaint had been a snapping sparking noise!) and applying solder to the legs of one output transistor (it had been removed and replaced without solder by someone!), I'm now in a position to check the Quiescent Currents and Offsets. (the pots are chewed up as though someone's been having a merry old time with them!).
Does anyone know the correct procedure? Thanks in advance!
Kevin
Does anyone know the correct procedure? Thanks in advance!
Kevin
Well would you believe it's still on the repair bench, there's a weird fault I can't bottom out without schematics. When switched into standby, various relays drop out as I assume they should, then after a couple of seconds or so start to creep back in with a gradually louder buzzing noise. I've changed various electrolytics and drive transistors but this part of the circuit is very complicated and dodges about all over the place.
A while ago! But I have schematics if you need them. Just refurbished a TR850 myself. Very good amps. The soft start circuit is a little over complex IMO, and prone to failure by the sound of it. I designed a simpler one in place of it, quite a lot of effort, but all working now.
Hi Jim, thanks for the offer. I have the diagrams, in a fashion, although the standby switching part of the circuit is different to the one I have here; there have been several circuit revisions in its lifetime and the rest seems the same, just the part that is giving the trouble!!
Yes..it's still here; the customer is no longer interested in getting it fixed but it would be nice to sort it as a spare amp for my own use.
Yes..it's still here; the customer is no longer interested in getting it fixed but it would be nice to sort it as a spare amp for my own use.
Haha... ok, yes my one stayed on the bench for several years before I got around to it 
How interested are you in getting this going? I could maybe sketch the mods I did to mine on top of the C Audio schematics.... it did involve basically removing all of the soft start control circuitry and replacing it with a different, simpler circuit to drive the relays.
How interested are you in getting this going? I could maybe sketch the mods I did to mine on top of the C Audio schematics.... it did involve basically removing all of the soft start control circuitry and replacing it with a different, simpler circuit to drive the relays.
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