SWTPC 6800 issues again
ajp166 at verizon.net
Mon Nov 28 10:51:59 CST 2016
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?
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.
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