[Coco] More MPI mischief...

[Robert Gault]

Brian Blake wrote:

>> From my under-educated point of view, it appears to me that I am looking at
> only a few possibilities possibilities: Broken trace on the MPI (would that
> prevent the music from actually starting)? Weak power supply in the MPI
> (doesn't makes sense if the FD-501 works fine)? Piece of debris shorting
> pins 33/34 to pin 35? (I would assume grounding out pin 35 would kill all
> sound from the CoCo, this does not happen as I can play games loaded via the
> MPI and still have sound).
>
> Any other thoughts or suggestions?
>

Make sure that the Orc-90 is actually sending out sound by putting an AC 
voltmeter on the output RCA jacks or connecting them to a sound system. If these 
have sound, then there may be a problem with the Orc-90 opamp IC6 or the Coco 
DAC is not getting sound from the CART input.
You may be able to test the Orc-90 IC with the pak open so a meter reading at 
IC6 pin1 can be made.
If you have some other sound source that you can safely connect to the CART port 
pin 35 even through the Orc-90, you can test the Coco side. Just remember to 
turn on the Coco sound and point the MUX at the CART.