Re: System Bad 01010001

["Mark Cummings" <NOTfigjams@primus.com.au>]

If it is a RAM fault, and I suspect it will be by the checkerboard
description, the board is certainly fixable.

I also got my first (and only) ROM-3 that was a no-goer.

The symptoms were:
1. Failed to boot.
2. No Post beep (from the speaker)
3. Random graphics on the screen. (I think they were flickering too, but
can't remember for sure)
I did not get a System Bad error (or at least could not read the screen to
see if there was one)

Using a circuit diagram I discovered the IRQ-L line was stuck low. This is
abnormal. Since the IRQ-L was connected to several VLSI surfave mounted
chips I could not isolate the problem.

After swapping the few socketed chips without success, I decided to exchange
all the DRAM chips with know good chips. This required desoldering all the
RAM chips. I did a few at a time.
At first I tried the Standard RAM at UK1, 2, 3, & 4 by trying them in a
socketed //e. they were OK.
Then I tried the Sound RAM at UK5, & 6 in a socketed //e.
Then I tried the FAST RAM at UE9, 10, & 11 in my 4MB GS Juice Plus (in
another GS), they were OK.
Finally I got lucky with the FAST RAM at UE8 which failed in the 4M RAM
card.
Replaced that chip with one from an old PC ram card, it was a
KM41C1000AP-10.

That fixed the ROM-3.

If I had to do another one I'd start at the FAST RAM as this is the most
likely cause of the problem. I don't know why I did the sound RAM, just a
bad hunch.

Also because the DRAMs are soldered onto a ROM-3, I would suggest you
replace them with IC-Sockets as you go, and get an experienced electronics
tech with a professional desoldering tool to remove the old chips, because
they can be reused if removed carefully. also the board is easily damaged if
appropriate care is not taken.

hope that helps,

I you were in Oz, I'd be happy to assist in the repairs. Postage from
overseas would be prohibitive.

Mark



"Herbert Fung" <lemonherb1@netscape.net> wrote in message
news:6qGa9.215059$Ag2.11116788@news2.calgary.shaw.ca...
> Well I bought a second hand ROM 3 motherboard that was untested as is.
>
> When I turn it on I get a checkered screen, and a four finger salute
yeilds
> a System Bad 01010001 error.
>
> Is there a way to decode the particular error to see if it's possible to
fix
> the board, or should I just turf it?
>
>