On Nov 24, 7:25*pm, "Arfa Daily" wrote:
"Eeyore" wrote in message

...







Arfa Daily wrote:

Does anyone have a set of schematics for the C-Audio RA3001 that they
could
let me have fairly urgently please ?

It's not a 'head', it's a 19" rack mounting pro power amp with line level
inputs. What do you want to know btw ? They are notoriously unreliable.
First
job is to replace all the PSU caps that have been cooked by the hot
exhaust air.
Then check how many mosfets are open.

I know an awful lot about it, having rejected it as an ODM product for
Studiomaster. I think *it was that model.

The links to the service manual on the supposed C-Audio 'website', just
seem
to take you round in ever decreasing circles via other third party
vendors
of everthing you can imagine.

Harman UK bought them. And I could tell you a story about that too ! Ask
there.
Except it's not Harman any more it seems but google that for starters.
They've
moved to Letchworth. I think most of the C-Audio parts ended up shuffled
into a
corner (I could tell another story) so they might be willing to get rid of
some
unwanted and unloved bits. Unless they already put them in a skip
(dumpster for
USAans)

Graham

The guy who owns the shop where all this stuff comes from, and who is a
musician himself with 'many years in', tends to call anything that's rack
mount, line input and 'power', a "head", as opposed to an "amp" for an
instrument level standalone unit like a Marshall, or a "combo" for the same
thing with speakers built in like an AC30 or Fender Twin. I just follow his
lead, and call them the same. What do you describe as a "head"?

Anyways, as to what's wrong with it. The "A" channel has an *extremely*
asymmetric output. On a sine wave, looks like the output from a half wave
reccy with no filter cap on the end. It also 'bounces' in amplitude when the
input level, or front panel level, is varied. The problem is right up the
front end somewhere. There are pukka sine waves around the TL074 input amp,
but soon after, the signal has taken on this asymmetry, which is then
faithfully amplified by the output stage. The "B" channel works perfectly,
so I guess I can start comparing between the two. Just would have been a lot
easier with a set of schematics to see where exactly the signal goes. It's
got that nasty 'feel' about it, that says it's going to be something like an
o/c resistor, which looks perfect to the naked eye ...

I see a couple of bunches of four TO92 transistors, so I think that may be a
good place to start looking.

Arfa- Hide quoted text -

- Show quoted text -

On the western side of the big pond, "head" can mean what you folks on
the eastern side, I believe, call the "Loo". Think it comes from
nautical background when the in-ship toilet was at the front/head of
the ship/boat.

Bob H