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

[Brian Blake]

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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