C-Audio schematic?
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From: Gareth Magennis on 2 Jul 2008 05:42 "Joe Kotroczo" <kotroczo(a)mac.com> wrote in message news:C490438C.5B21A%kotroczo(a)mac.com... > On 1/07/08 14:02, in article 486A1CB8.A7839A4C(a)hotmail.com, "Eeyore" > <rabbitsfriendsandrelations(a)hotmail.com> wrote: > > (...) >>>>> And: does anybody happen to have a schematic for a C-Audio ST600 >>>>> amplifier? >> >> Well I did once. God only knows where it is now after 3 company moves. >> >> >>>> 2u job ? With one puny fan at the back blowing blistering hot air over >>>> the >>>> reservoir caps at the front ? >>>> >>>> If it's the model I think it is, I could tell you a thing or two about >>>> that. >>> >>> It's a 2U job, with a single fan in the back, but the front half only >>> contains a big transformer. >>> >>> It's this one: http://www.gbaudio.co.uk/data/st600.htm >> >> That's the one ! I'll save the story of shame for later. > > I've put the pictures here: > http://homepage.mac.com/kotroczo/PhotoAlbum62.html > > Am I right in assuming that the left side should be the same as the right > side? Same value resistors? It looks like that, but I'd rather be safe > than > sorry. > > -- > Joe Kotroczo kotroczo(a)mac.com > Those 3 power resistors that look burnt are possibly part of the Zobel network. If you simply replace them they may just go again until you find why they burnt, which may be RF oscillations. Check also the capacitor(s) in this network, or better still just replace it as well. And the one on the other side for good measure. The old C Audio RA series used to sometimes suffer from RF problems and subsequent burnt Zobel networks, I heard it was some kind of poor grounding design, maybe someone else here could elaborate on causes and/or cures. Gareth.
From: Eeyore on 2 Jul 2008 14:31 Phil Allison wrote: > "Eeysore" > > > I see they've changed the internal layout a bit too, replacing the more > > durable metal can output devices with plastic encapsulated ones. > > > > Check for symettrical clipping btw. They EAT output devices by running > > them too hot > > which then fail 'open' so it's not initially obvious. > > ** Plastic pack lateral MOSFETS do not fail open - since there are no > fusible drain bonding wires as in the TO3 kind. You know, I did wonder when I mentioned that. I'd originally imagined it was a die failure mode thing. So, did Hitachi simply use wimpy bonding wire compared to say Motorola ? Of course the big MOT devices used those damn 'prongs' didn't they. Geaham
From: Eeyore on 2 Jul 2008 14:36 Gareth Magennis wrote: > "Joe Kotroczo" wrote > >"Eeyore" wrote: > > > >>>>> And: does anybody happen to have a schematic for a C-Audio ST600 > >>>>> amplifier? > >> > >> Well I did once. God only knows where it is now after 3 company moves. > >> > >>>> 2u job ? With one puny fan at the back blowing blistering hot air over > >>>> the reservoir caps at the front ? > >>>> > >>>> If it's the model I think it is, I could tell you a thing or two about > >>>> that. > >>> > >>> It's a 2U job, with a single fan in the back, but the front half only > >>> contains a big transformer. > >>> > >>> It's this one: http://www.gbaudio.co.uk/data/st600.htm > >> > >> That's the one ! I'll save the story of shame for later. > > > > I've put the pictures here: > > http://homepage.mac.com/kotroczo/PhotoAlbum62.html > > > > Am I right in assuming that the left side should be the same as the right > > side? Same value resistors? It looks like that, but I'd rather be safe > > than sorry. > > Those 3 power resistors that look burnt are possibly part of the Zobel > network. If you simply replace them they may just go again until you find > why they burnt, which may be RF oscillations. Agree 100%. Or inadvertent 'RF' on the input. > Check also the capacitor(s) > in this network, or better still just replace it as well. And the one on > the other side for good measure. Not quite sure why you suggest that, unless they're physically burnt. > The old C Audio RA series used to sometimes suffer from RF problems and > subsequent burnt Zobel networks, I heard it was some kind of poor grounding > design, maybe someone else here could elaborate on causes and/or cures. Well, I always thought they were a bit over-rated. I know someone who was involved in designing the early ones and he wasn't what I'd call an analogue design guy. Graham
From: Eeyore on 2 Jul 2008 14:38 Phil Allison wrote: > "Gareth Magennis" > > > > Those 3 power resistors that look burnt are possibly part of the Zobel > > network. If you simply replace them they may just go again until you find > > why they burnt, which may be RF oscillations. > > ** RF oscillation - BOLLOCKS !!! > > Supersonic frequency oscillation is the only cause. Ultrasonic. Come one - we're saying the same thing here. Don't argue over it. Please ? Graham
From: Eeyore on 2 Jul 2008 14:39
Gareth Magennis wrote: > By the way, "supersonic" is a bit last year, don't you think? Concorde's no longer in service ! :-( Graham |