low voltage to radio?

[Andy Schor]

> [Original Message]
> From: Will Ng <wng-audi at verizon.net>
> To: <walbum at earthlink.net>; <quattro at audifans.com>
> Date: 1/9/2005 3:32:10 AM
> Subject: Re: low voltage to radio?
>
> At 03:17 PM 1/7/2005, Andy Schor wrote:
> >My aftermarket Blaupunkt radio sometimes won't play when turned on.  The
> >lights light up and it cycles through all of the functions on the screen
> >(without being prompted) while the faceplate is attached and the unit is
> >turned off.  When I press the power button, it lights up but there is no
> >output (sound).  The CD player shows the track and time displays, still
no
> >sound.  The red power lead is connected to the relay panel
> >up under the dash (behind knee bolster), the yellow lead is connected to
> >the yellow in the harness.
> >I'm not an electrical engineer, but is it possible that there's enough
> >juice to turn the unit on, but not enough to power it?
> >Something else?
> >
> >Andy Schor
> >'91 200q20v Avant
>
>
> Check you grounds. The GND wire from the radio may be loose or not
grounded 
> to a good source.
> The radio may be getting a poor ground from the antenna lead's shielding.
>
> Most modern 'high powered' stereo head units use the constant +12V input
to 
> not only preserve clock and station memory functions, but can be part of 
> the tuner's power circuit.
> True of Concord stereos of old.
> Some high end head units are wired like amplifiers. The high amperage
+12V 
> input is a constant, and the on/off by ignition switch is served by a 
> switched +12V input. True of current Eclipse models.
>
> HTH,
> Will
> 1990 200q PITA

I have suspected a possible ground issue, will have to pull the stereo and
trace the wiring.  The condition is the same regardless of source (radio or
CD).  When turned on the lights and output meter displays work as if
nothing is wrong, but there is no sound.  When I turn the unit off it first
displays the clock, then cycles through screens for all features (such as
Bass, Treble, Clockset, CD functions, "Blaupunkt Advantage", etc.).  The
condition used to occur sporadically but when it worked, it worked just
fine.  Sometimes it would come on after shutting off and restarting the
car,  now even that doesn't work (yet I keep trying).  Is it possible that
the tuner/CD player is getting power but the amplifier section is not?  Is
that what you suggested Will?  It isn't a fancy high end audiophile unit,
it has an internal amplifier.  Unlike Brett's radio, mine would work fine
(not shut down) until it or the car was turned off.  It just wouldn't come
on the next time.

Andy Schor
'91 200q20v Avant