[Coco] MPI problem or ...???

[mike delyea]

Just my 2 cents but wouldn't the DECB 1.1 problem be on the floppy
controller?  Thats where the DECB ROM is.

On 6/19/07, Brian Blake <random_rodder at yahoo.com> wrote:
>
> Okay some more testing done...
>
> I changed around the devices and the slot number the switch is set to and
> got the same results. Then I took everything except the FD-502 and also
> plugged Mega_Bug into slot 1, with the switch set to 4, and it booted to
> DECB 1.1. Turned everyrthing off and put the switch on slot 1 and Mega-Bug
> started fine. The only pak that seems to allow proper booting is the SS/C.
>
> I opened up the case, and there has been a mod that looks like a PAL
> upgrade. I did loosen up the transistor, made sure there was no oxidation
> and re-tightened it. The big cap looks fine, no swelling or leaking visible.
> I didn't take the board all the way off and check all of thw solder joints,
> figured I'd do that next weekend. In the mean time, any other suggestions?
>
> Thanks for the help guys,
>
> Brian
>
>
>
> ----- Original Message ----
> From: Brian Blake <random_rodder at yahoo.com>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Sent: Tuesday, June 19, 2007 11:43:50 AM
> Subject: Re: [Coco] MPI problem or ...???
>
>
> Mark and Robert,
>
> Thanks for your replies. I will look for both of these problems tonight.
>
>
> Thanks again,
>
> Brian
>
>
>
>
> ----- Original Message ----
> From: Mark Marlette <mark at cloud9tech.com>
> To: coco at maltedmedia.com
> Sent: Tuesday, June 19, 2007 11:13:52 AM
> Subject: Re: [Coco] MPI problem or ...???
>
>
> There is also a large electrolytic cap that after 10-20 years might be
> a bit dry.......
>
> Mark
> Cloud-9
>
> Quoting Robert Gault <robert.gault at worldnet.att.net>:
>
> > Brian Blake wrote:
> >
> >> Greetings all. I ran into a problem with my MPI this weekend.
> >> <snip>
> >> Then, I tried another 512k CoCo 3. First, with just the FD-502 and
> >> everything works fine. Next, the MPI and FD-502 in slot 4, everything
> >> worked. Then the SS/C in slot 3, everything works fine. Next up was
> >> with the O-90 in slot 2. Not fine... I noticed immediately that it was
> >> booting to DECB 1.1 instead of 2.1. ><snip>
> >
> >  This type of problem looks like a power supply defect in the MPI. Load
> > up enough devices and the MPI flakes out.
> >  A good test for this is to change the order of paks and their
> > positions in the MPI. For example, what happens with an MPI, a disk
> > controller in slot1, the ORC-90 pak in slot4, and the MPI switch at
> > slot1? If the Coco will power up in DOS 2.1, the problem is not with
> > the ORC-90 pak. It will either be a non-modified MPI or power supply
> > problem.
> >  A test of modified vs non-modified, is to start a Coco3 without an MPI
> > and PEEK $FF90-$FF99, see what the values are, plug in the MPI and see
> > if the values change. If the values change, the MPI most likely is not
> > modified for Coco3 use.
> >  Power supply failure normally is a loose or oxidized contact on the
> > main power transistor. This is caused by a screw making a bad contact
> > with the transistor case. Loosen the screw/lock washer and re-tighten
> > it. That should improve the situation.
> >
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > http://five.pairlist.net/mailman/listinfo/coco
>
>
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