22 Nov
2006
22 Nov
'06
5:40 p.m.
Hi Tony
Yes, there is activity in the address lines at least.
I would beleive is gets hung on something. I can see
some activity for a breif period in different parts
of the board. like it was in self test. Then it looks
like it gets hung. Not sure what type of a Processor
it uses, but watching the address lines on the roms
it starts out Ok. With all of the Error codes in the
manual and none being displayed, It would have to be
a very low level problem.
It would be worth identifying the processor...
My experience is that if a peocessor-based system gets really confused
(as this one seems to be), then quite often the RAM or RAM control
circuitry is to blame (for example if the stack can't be stored correctly
in RAM, the system will go into lala land at the first RETurn
instruction). ROM and processor failures, while also possible, seem to be
a lot less common.
As Dave pointed out, it's not a true DEC item.
So with out much to go off of it would be a long up
hill battle.
Do the chips have recognisable numbers, or are they house-coded?
-tony