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

[Gene Heskett]

On Thursday 21 June 2007, Brian Blake wrote:
>John,
>
>Yes I do.
>
>Not having a service manual for this paricular unit I am currently thinking
> one of the IC's is bad, just had not gotten the scope out to look at any of
> the outputs. Just don't know where to start looking at this moment...
>
>George,
>
>Again, I haven't actually got the scope out to look, but, the DMM isn't
> picking up anything greater than .001vac. I'm not thinking that's enough to
> cause these problems, but, again, I've only recently got back to CoCoing...
>
>
>Thanks guys, keep the good info coming!!!!
>
>Brian  (<- not an expert ;) )
>
A couple more things to check Brian since these things are nearly old enough 
to vote.

1. clean up all the blackened coating on the card edge connector that plugs 
into the coco.  Get brutal, as in a small piece of 0000 steel wool and some 
contact cleaner & make it shine on both top and bottoom, and that includes 
those 'ears' on each side as they are the main ground connection between the 
coco and the mpi.  Just don't power it up till all the steel wool has been 
removed.  That black stuff is just as good an insulator as that same black on 
a battery post of your car battery.  I got so tired of that that I sawed it 
off, found a pc card with a gold plated finger pattern, and transplanted it.  
That very tedious job was 15 years ago, and haven't had any problems with 
that since.

2.  If that mpi has not had the usual jumpering of all the card socket pin 8's 
together, there is a probable problem there because the slot selection switch 
has become oxidized and needs to be given a shot of cleaner and exercised.  
Lots of exercise, then a couple more shots of contact cleaner.

Gene, a C.E.T.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
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- Joe Crowe