Re: '90 Coupe Quattro stereo

[Andrew Duane USG/PE <duane@zk3.dec.com>]

Hairy green toads from Mars made Phil Payne say:
> 
> In message <941210190133_76030.63_HHB25-1@CompuServe.COM> "Timothy P. Gallagher" writes:
> > I experience engine noise through my 1990 Audi Coupe Quattro
> > factory-installed AM/FM/cassette stereo;
> 
> My first question would be: engine noise or alternator noise?  Sharp rattling 
> spikes or an intrusive whine?  What does the noise sound like?

I have a similar problem in my '89 100Q, but with the aftermarket CD
player I installed.  My noise is a whine that matches engine speed. The
whine increases greatly under heavy electrical load: A/C, rear window
defrost, high beams, etc.  I assume this is alternator noise.

The installer added a line level adaptor to raise (lower?) the signal
level at the rear speakers, which helped a lot, but didn't cure it.
Since the noise is pretty much the rear (amplified) speakers only,
I assume the amplifiers are picking something up from the +12VDC.

> Audi in Germany used to publish a very helpful and very simple little leaflet 
> on "Funkentstoerung in Audi Fahrzeuge" or some such.  There was a companion 
> leaflet entitled "Kurzwellenempfang in Audi Fahrzeuge".  They were very 
> good. I've forgotten the exact check order, but it was basically ignition 
> suppression, alternator suppression, radio power lead choke, engine bay 
> grounding straps, motor hood grounding strap (extra) and then various small
> and cheap suppression capacitors.
>  
> But they both made the point that most users will find Audis perfectly
> suppressed - adequate even for sensitive amateur radio equipment.
> 
> Your comment about "wiring filter" raises a minor concern.  This sounds like
> a choke in-line in the radio's power lead.  It's a band-aid to circumvent a
> problem - and in my (personal) experience it's never completely satisfactory.
> It's much better to identify the source of the signal - Audis are generally
> very well suppressed and most radios won't pick up a glimmer of a problem.

Do yuo have those booklets, and could you post some of the things
to check? I'm going to go through and make sure all of my connections
in the engine are clean and tight. Any specific ones to look at?

-- 

Andrew L. Duane (JOT-7)			duane@zk3.dec.com
Digital Equipment Corporation		(603)-881-1294
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Only my cat shares my opinions, and she's clean, but not wrapped too tight.