SWTPC 6800 issues again

[allison]

On 11/28/16 11:22 AM, Brad H wrote:
> Hey guys,
>
>   
>
> You might recall a while back I was having issues where I'd have to power
> up/power off multiple times before I'd get the 6800 to start up correctly
> and give me the SWTBUG prompt.  What I did was remove an overwrought
> modified RAM board and replaced it with a more basic 4K board set to the
> $A000 range.  That worked great for a while, but not we're getting back to
> the situation where I power up many times and get either ? marks, a string
> of 4s, or some other random character.  I have to power off and on several
> times before I get the $ prompt.
>
>   
>
> I figured out how to run a proper RAM diagnostic and no errors came back.  I
> wasn't sure how to properly test the $A000 board -  I assumed I couldn't let
> the test test the address space used by the test program itself, so I set it
> to run from A07F to AFFF (I think I did that right, I set the MSB in A002 to
> A0 and LSB in A003 to 7F, and for the upper limit MSB in A004 to AF and A005
> to FF).
>
>   
>
> I'm wondering now if this is really a RAM problem or maybe something else.
> I don't think it's the serial card.. I've tried both the MP-C and MP-S and
> no change.
>
>   
>
> I have an NOS MP-B2 motherboard here.  The 'check pins' on the molex
> connectors for the cards haven't even been cut.  I could set that up for
> testing although, being totally unused I'm hesitant about altering it.  What
> do you think on that?
>
>   
>
> Brad
>
>
Before you do anything try this.  Remove and reinsert each card and see 
if the system behaves normally
afterward.  If it does you have crusty/corroded connectors!  This was a 
problem with those molex pins
at times.  If that's the case a good cleaning may insure that does not 
reappear, for a while.

it can also be one or two pins that have cracked solder joints and are 
in need of resolder.

Allison