Karl's stereo interference

["Graham Hilder" <graham.hilder@domain.elided>]

Re Karl's query in No.1478, high-pitched interference in the stereo, I =
think this description sounds more like alternator whine than ignition =
noise,  although either can occur of course.  To fix it, usually the first =
attack is to simply make sure the orginal suppression components are still =
present on the alternator, and cleanly connected and serviceable - usually =
it's just a single capacitor somewhere at the alternator output. (Well =
that's how it is on all my older Alfas - modern ones may differ - can =
someone else help in that regard?).

If the alternator suppression is confirmed OK, next identify if your noise =
occurs on radio only, or tape only, or both.   If on radio only, it's =
probably coming in via the radio antenna, and I'd check out the antenna =
connections, both the live and the earth, and at both ends. Especially =
make sure the antenna coax braid is solidly and cleanly earthed. Sometimes =
it is also necesary to directly earth your stereo with a good short cable =
from the stereo's metal case to some nearby clean metalwork of car body.

If your noise occurs on tape only, or both radio and tape, it's probably =
coming in via the radio power input.  Many stereos have noise suppression =
filters on the power input, either externally or internally. Check this =
all present and correct.=20

Hope this helps.   Alternator whine isn' t usually a big deal to suppress. =
 Ignition noise can sometimes be a lot more difficult.  =20

Have you always had this problem or has it just developed?   If it used to =
be OK, then at least you know there's nothing fundamentally wrong with the =
car suppression or the stereo installtion, just a temporary fault to find.

Best regards,=20
Graham in NZ.=20
71 GTV, 78 Alfetta GT, 82-82-84 Alfa Suds=20

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