IBM 5160 oddball fault

[Jules Richardson]

On 04/23/2015 04:55 PM, Jules Richardson wrote:
>> Have you tried the CGA card in different slots? Just in case it's a bad
>> contact
>> on the edge connector.
>
> Yes - the same thought had occurred to me.

Aha! I'd tried it in slot six (originally it was in seven) with the same 
result, and then I gave it a go in slot five too, just to confirm that it 
wasn't 'luck' that two slots were bad - the problem remained.

Now while I had the system board out of the machine (as it makes it easier 
to poke around the bus signals without a riser card / extender), I figured 
I'd try the other slots just to verify that they were all bad.

Well, it worked in slots 2 and 3 (I didn't try 1 as I've got a hazy memory 
telling me there's something different about that one), but was failing in 
slots 4 and up.

There was no visible damage to the PCB, but checking with a meter showed 
there to be a break in continuity on A11 between slots 3 and 4, so I've now 
bridged them with a wire, and all is now working OK :-)

cheers,

Jules







Checking with a meter, it seems that I've got a break in the PCB track for 
A11 between slots three and four. There's no visible damage

> I'll take a look at the address lines (albeit just with a DMM, but that
> will hopefully be enough if it's a stuck bit)
>
> cheers
>
> Jules
>
>