Date: Wed, 8 Sep 2004 19:56:44 +0000
Reply-To: Zach White <zwhite@DARKSTAR.FROP.ORG>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Zach White <zwhite@DARKSTAR.FROP.ORG>
Subject: Re: Using FM stereo for film soundtrack: tach effect
In-Reply-To: <vanagon%2004090813500103@GERRY.VANAGON.COM>
Content-Type: text/plain; charset=US-ASCII; format=flowed
On Sep 8, 2004, at 17:42, Scott Norville wrote:
> I sat down to ask a question and found this similar stream. I have a
> Panasonic CD player installed, it has a front-mounted aux. jack. This
> works
> great for the DVD on the iBook with the van parked, idling (or coasting
> downhill with the engine off...) but I get too much ignition
> interference
> (whine that increases frequency and intensity with with engine speed)
> with
> the engine running. Anyone know of any type of shielding for this
> function?
>
Scott,
That sounds to me like a ground loop (Not the right term when dealing
with a DC system, but same basic concept, IIRC). If you've never had
to track one down, you're in for a lot of rewiring. Even if you have
had to track one down, you may be in for a lot of rewiring. :)
The suggestion to try swapping the cables between the laptop and stereo
is good, as it's cheap and easy to do, but my gut feeling says that's
not the problem in this case. You should also try another audio source,
such as an ipod or portable cd player. Again, a long shot, but cheap
and easy to check. If the problem still persists, keep reading.
The first thing to do is to check all the connections on your stereo.
See where it's pulling power from, try running the stereo on only the
"hot" wire (the one that actually powers the system, not the one that
supplies constant power for the radio's settings). See if your speakers
are wired with a common ground or if they have a separate ground for
each speaker. Some stereos want the ground to each speaker separate,
some want it to be common. My van came with the speaker grounds wires
all tied together, I'm not sure if this is common in vanagons.
You may also try running the stereo directly off the battery, see if
that corrects the problem.
Replace the wires between the speakers and the stereo. This is not easy
to do in the case of the rear speakers, however. You might try running
just the front speakers, if the problem goes away, you know where to
concentrate on.
If none of that works, the next thing to check is your ignition system.
Make sure all connections (especially the coil to cap and cap to plugs)
are tight, the wires good, etc. While you're there, apply some
dielectric grease, which will help suppress RFI and help the connection
last longer.
If none of that helps, you have two possibilities. One is that your
stereo isn't properly designed to keep out RFI. It sucks, but it
happens. The other is that you have wires that are shorting somewhere
they shouldn't be, commonly a ground shorting to the chassis in the
wrong spot. Normal visual checks and troubleshooting procedures for the
electrical system apply here.
Finally, the problem may be poor ground connections. Check the ground
terminals behind the fusebox, make sure they're clean and you're
getting good ground there. Run the ground for the stereo straight to
the battery, sometimes that will clear up the problem. Some people
don't recommend this for various reasons, but sometimes it works, and
personally, I can't see any reason why you shouldn't do this. (Someone
please correct me if you know _why_ I'm wrong, here.)
This probably isn't what you wanted to hear, but installing "shielding"
is actually harder than this, when done right. Plus, the stereo is
already shielded, but because something in the wiring is wrong, the
shielding is being bypassed. More shielding won't really help.
-Zach
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