Troubleshooting a 286.. oscope level!

[Tothwolf]

On Sat, 3 Oct 2015, ethan at 757.org wrote:

> I might be able to get hold of the bios, but I'm worried about the 3rd 
> EPROM. It sits in the middle of a bunch of Yamaha branded chips. The 
> BIOS chips are in the middle of a Chips & Technologies 286 chipset 
> group. The people I find might be able to dump the BIOS via dos program 
> but not that 3rd IC. But at least if I could split the one I could 
> compare it.
>
> Here are mainboard pics I took when doing the cap replacement:
> http://imgur.com/a/CQHcy
> I might recheck that mess near C113

Did you only replace those small green Nichicon parts? If so, I would 
inspect/test the others as well. My experience with these type of early 
mixed SMD/through-hole boards is that some companies tried to reflow them 
with the small electrolytics already in place which would damage their 
seals and cause them to leak as they aged. It doesn't seem to be specific 
to any particular brand/series either as I've seen Nichicon, Nippon, 
Panasonic, etc all affected by this.

If a new set of BIOS EPROMs doesn't fix it, it might be time to look into 
an in circuit emulator for the 80286. PODs for LCC sockets do exist, 
although they might be harder to find than a POD for the PLCC or PGA 
versions.