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

[Mark Marlette]

I know on the 26-3024 the cap is 10,000uF 35V. Can't miss it. :) Or  
you can get a cold solder joint. I had one that I couldn't find the  
problem and after about 6 months or work/no work, I had it pin pointed  
to the cap, just touch it and you would get different results.

Mark
Cl.oud-9

BTW: There is no such thing as a bad CoCo device!!! We fix them all. :)



Quoting Brian Blake <random_rodder at yahoo.com>:

> 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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