[Coco] Erratic MPI Behavior

[Ray Watts]

Boisy G. Pitre wrote:

> Folks,
>
> I have a 26-3124 MPI, upgraded for the CoCo 3, that behaves in the 
> following manner:
>
> 90% of the time, with a working disk controller and DOS in slot 4 and 
> the switch at that position, the CoCo 3 fires up in ECB, not Disk 
> BASIC. If I turn the CoCo and MPI off and on enough times, it will 
> eventually fire up into Disk BASIC, but a power cycle usually results 
> in the ECB screen again.
>
> This is a major annoyance.  Another MPI of the same model, also 
> upgraded, works consistently in place of this one.  Something is wrong 
> with this Multi-Pak.
>
> I've scrubbed both sides of the card edge connector with an eraser 
> thinking that dirty leads might be the cause.  Still, the same 
> behavior persists.
>
> Does anyone have any possible ideas on what this might be?
>
> Boisy
>
>
That's interesting, Boisy, because I have been having the same problem 
for several years ... except that it ONLY happens when connected to a 
5.25" drive and NEVER when connected to a 3.5"drive.  I have 34 
conductor pigtails coming off each size drive so I can switch drive 0 on 
that system. I just assumed the 5.25" connector was a little flakey and 
was too lazy to remake it.  But the symptoms are identical to yours. 
 What makes it more difficult for me is that it is the system with a 
pair of ST-225's and I have to bring the system up in order to shut them 
down.  I sometimes get results by ***gently*** jiggling the floppy and 
HD controllers in the MPI sockets, but it might just be random luck. 
 I'll look into it a little more thoroughly and let you know if I find 
anything.

Griz