nope...we replaced the plugs and wires here in the shop with resistor units
(after the noise started, but it didn't help). we're gonna test and replace
the capacitor soon (time is an issue for this customer) c'mon! no other
thoughts?

most of the noise faq's and such I've seen all focus and centre around
alternator noise. (arg!) I've done the "remove ground" and see what
happens, and the noise goes away, so its a power system issue...not being
induced in the signal (on the way in) or the speaker leads (on the way out).

?

Hamilton Audio
Car Audio, Security & Performance

"Kevin McMurtrie" wrote in message
...
In article ,
"Hamilton Audio" wrote:

Did a pretty simple install in a customers vehicle last week (decent
head
unit, large 4 channel amp, door pods with 6.5s, and a pair of 10's).
The
job went well till I fired up the engine!! The truck is a 1987 Chevy
reg
cab with carbed 350 and HEI ignition.

Its definitely not alternator whine. More of a loud "buzz" that varies
slightly with rpm. What I did:

-- pulled the alternator belt and unplugged it. ran the truck, no cure
(needed a belt change anyway!)
-- aftermarket tach disconnected (thought it was backfeeding), no cure
-- unplug the head unit, disconnect rcas, no cure. (obviously not
signal
related)
-- changed my 4 ga. ground to about 4 different solid points, none
helped
-- used jumper cables to ground back to the battery temporarily, no cure
-- changed out spark plugs and plug wires with fresh resistor type
units, no
cure

As a side note, this truck also causes interference in televisions as it
drives by, so its pumping off some extremely big rf noise! The last
thing
we're gonna try later on is replacing the capacitor in the distributor
that
the manual says is for nothing more than RFI suppression. Can anyone
suggest anything else to look at for ignition noise? The truck has no
computers or anything in it.

Perhaps this may help...a while back (with the stock system), the
alternator's regulator failed, sending the output voltage gauge off the
end
(over 18 volts). at that moment, the factory deck/speakers began
buzzing
painfully loud. turning the deck off didn't kill the noise. changing
out
the alternator fixed it, but we figure something else in the vehicle was
damaged/destroyed by the voltage spike, now causing the intereference.

any ideas??

Hamilton Audio
Car Audio, Security & Performance




An ignition problem would be my guess. Check the ignition capacitor, as
you mentioned. Also make sure that the owner didn't do anything stupid
like replace the resistor wires and plugs with solid conductor types.