Re[2]: Radio or speaker problem

[jtessman@enron.com]

     Phil;
     
     I went through the same scenario with my V8Q, one of the rear 
     speaker/amp/eq systems went south. I hunted around town until I found 
     a shop with some experience on Bose OEM systems. They pulled the unit 
     (rears are very easy) and systematically swapped out the capacitors 
     until the problem went away. Heat and age seems to be the biggest 
     culprits in the demise of these electrolytic caps.
     
     The whole thing took 2 days and cost me $40! Problem hasn't reappeared 
     since. I would have done it myself with a handfull of caps from 
     Radioshack but they use a heavy adhesive to protect the parts from 
     vibration and it is tedious to remove. Anyway, it was the best $40 I 
     ever spent on an Audi!
     
     Cheers...jon
     
     Jon Tessman
     '90 V8Q
     '94 Miata M Edition
     '79 Moto Guzzi Lemans II


______________________________ Reply Separator _________________________________
Subject: re: Radio or speaker problem
Author:  Phil Rose <pjrose@servtech.com> at ENRON-Internet
Date:    7/31/98 9:39 AM


>Date: Thu, 30 Jul 1998 20:33:18 -0400 
>From: Mike Arman <armanmik@n-jcenter.com> 
>Subject: Radio or speaker problem
>
     
>This noise is called "motorboating" and usually appears when one of the 
>power supply filter capacitors has gone open. This applies to AC-line 
>powered radios, and I don't know what's inside the Bose - it might have an 
>inverter and some rectifiers if anything in the radio needs more than 12 
>volts.
>
>It isn't a speaker problem - sounds like a bad power amp chip if it is on 
>one side or one end of the car only, but if it is everywhere, it's the 
>power supply.
>
>Upgrade time . . . (boo!)
     
Mike,
Yes, "motorboating" is exactly the word I thought to use in my original 
post. You say "it isn't a speaker problem", but do you mean to rule out (as 
the problem) the amplifiers that are built into each speaker? If so, why?
     
Anyway, the noise is localized to the rear, but I haven't been able to tell 
yet if one or both sides are thundering (being at such low frequencies, it 
is hard to pinpoint the source 'till I disconnect some things).
     
BTW, I'm on record as being among the undiscriminating few who are 
reasonably satisfied with the OEM sound (gasp!) So I really don't welcome 
the thought of going through an "upgrade", although I have no doubt that 
the sound would be improved. (I'd rather see the upgrade money go into 
Eurolights or a chip).
     
Phil
     
Phil Rose               Rochester, NY 
'89 100
'91 200q                pjrose@servtech.com