Northstar Computer, was Re: S100 spares needed - repairs almost done

From: Marvin Johnston <marvin_at_rain.org>
Date: Thu Jan 9 21:52:00 2003

"Richard A. Cini" wrote:
>
> Anyway, I'm having diskette issues. I have two theoretically good
> single-density controllers and disk drives, and Don Maslin made replacement
> boot disks for me. These disks don't boot, although the controller attempts
> to access them. It may be that the replacement SD disks were made from a DD
> controller, but I don't know for sure.
>
> So, I have two choices -- obtain SD boot diskettes made with an SD
> controller or get a N* DD controller (MDS-AD|AD2|AD3). Any other thoughts or
> recommendations appreciated. Thanks.

I have a similar problem with three of my N* computers, and finally
decided to find out what was going on. The DC voltages were okay and
there only appeared to be about .2 VAC ripple on the line; I think that
is okay. By doing board swaps, I found out the CPU and MDS cards were
good and the disk light would come on w/o any memory installed.
Interesting! One of the memory cards appears to be bad. Doing board
swaps to a good machine and everything works. I am down to one of two
things, either the motherboard has some problems, or the memory card is
bad. I was using 64K RAM boards, and since I didn't pull out the docs to
double check, it is possible the "bad" ram card had the E800 segment
turned on (that is the location of the N* boot routines.) Yes, I did
swap disk drives also in the process.
Did I mention that I heard a couple of "pops" on the CPU card when
apparently the tantalum caps shorted and exploded :). One of the CPU
cards had a trace burn off when the cap went.
Received on Thu Jan 09 2003 - 21:52:00 GMT