From: Joe Kotroczo on
On 2/07/08 11:42, in article FdOdnT9R57Xo0PbVRVnyugA(a)bt.com, "Gareth
Magennis" <sound.service(a)btconnect.com> wrote:

(...)
>>
>> 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. 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.

Thanks for the info.


--
Joe Kotroczo kotroczo(a)mac.com

From: Joe Kotroczo on
On 2/07/08 2:32, in article 486ACCB1.9ACB46A(a)hotmail.com, "Eeyore"
<rabbitsfriendsandrelations(a)hotmail.com> wrote:


>> 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.
>
> I'd say that's a pretty safe assumption. Odd parts to burn out though, tends
> to suggest 'RF' oscillation on that channel perhaps, or RF on the input.
>
> 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.

Thanks.


--
Joe Kotroczo kotroczo(a)mac.com

From: Phil Allison on

"Rupert"

'Ultrasonic' would be the correct term. Common mistake just like
calling 'infrasonic' "subsonic." No such thing as a subsonic filter,


** Wot idiotic pedantic twaddle.

What IS common usage IS correct !!!!

The terms " supersonic oscillation " and " subsonic filter " ARE the
correct terms cos they are part of audio electronics jargon.



...... Phil



From: Phil Allison on

<bob(a)yeruncle.com>
>
>
> To be technically correct, RF would apply to any frequency capable of
> generating
> radio waves,


** WRONG.

The context being * audio amps * makes it wrong usage.



....... Phil






From: Phil Allison on

"Eeysore rabid fuckwit and lying charlatan "

>
>> Well actually it was to clear up whether "RF" is the correct term for the
>> frequencies involved or not.


** The * correct term* is the one in common uses for the matter.


> Yes, you can safely ignore Phyllis on this point.


** Very bad advice - from a very arrogant and stupid charlatan.


>> I have often heard such oscillations to be termed RF,


** By the terminally ignorant.


> Well, most ppl say 'RF' and leave it at that.


** Not where I live nor any audio electronics text I have seen.


>> Actually, it really doesn't matter that much, does it.


** The potential for misunderstanding the cause is ENORMOUS if you use the
term RF - cause that will get associated with radio mics and or radio / TV
broadcast signals being the cause of amplifier smoking.



....... Phil



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