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RE: Strange Car Stereo Problem

To: <triumphs@autox.team.net>
Subject: RE: Strange Car Stereo Problem
From: "Randall" <tr3driver@comcast.net>
Date: Fri, 7 Oct 2005 08:24:32 -0700
> It will also
> take a significant amount of time for the small amount of current that input
> uses to discharge the cap so the radio will continue to play after the key is
> switched off (although GM has made this a feature).

Except that GM still lets the engine shut down.  On your TR, the cap will also
supply power back into the ignition circuit, so the engine will also continue to
run until the cap is discharged.  But because of the current the engine is
drawing from the cap, it won't be long.

> Check the radio specs but usually this input is only a control signal and the
> main power comes through the constant feed.

Neither of my modern stereos specifies current draw at all, let alone which
power lead draws the most.  But one of them seems to draw most of it's power
from the switched input.  The more expensive, motorized one seems to draw mostly
from unswitched.

>  If the current is low enough a
> small resistor, say 22 ohms or so may be a good idea.
>
> On the other hand, if htis is only a control signal input it may be
> impervious to noise anyway.

True enough, it was just something to try.  OTOH, the fact it crashes implies a
bug of some sort, and fast noise and/or spikes above supply voltage might be
what it's sensitive to.

Randall


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