Troubleshooting a 286.. oscope level!

[Zane Healy]

On Oct 2, 2015, at 10:21 PM, ethan at 757.org wrote:

> Hello everyone,
> 
>  I'm working to troubleshoot a 286 laptop style computer. I've kind of hit the end of my knowledge and wondering if anyone has any insight.
> 
>  The computer in question I've never seen run. So I don't know normal behavior. There were a few caps inside that were leaking electrolyte, I cleaned it all up and replaced them. A few traces look a little bit corroded but test fine.
> 
>  First thing I'm thinking, is did the BIOS eproms loose a bit or two of data from age? Bit rot? I did read off the two BIOS chips (high and low pair I assume.) I can see text like Copyright Pheonix Technologies 1988, but I can see that for instance the first character of the text Copyright is wrong, it's a P in one file and 9A in the other.
> 
>  Second thing I hooked up Oscope and cut on computer. It never does a floppy seek. When I poke around the 27c256 EPROM I see constant activity on all address lines, and all datalines. This includes the OE pin as well. Would a normal runnng computer hit the BIOS that much?
> 
>  Any thoughts appreciated!
> 
> --
> Ethan O'Toole
> 


When you drop into BIOS, is anything actually set?  Can you set the time, and get it to stick?

I have a Twinhead 386sx/16 I bought new, the only thing I've used it for in the past 20 years is a serial terminal, and every time I go to boot it, I have to drop into BIOS, and configure things, as the BIOS battery is long dead.

Zane