Troubleshooting a 286.. oscope level!

ethan at ethan at
Sat Oct 3 23:10:32 CDT 2015

> 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.

I only replaced the one style that was leaking on the mainboard, there is 
also a bunch of others I think that are smaller.

On the driver board that runs the LCD I recapped it as well. I'll go back 
and look at the smaller caps. I put the oscope on the power lines and 
didn't see crazy ripple, but I only used an analog 20mhz tektronix not the 
crazy heavy old HP thing with the high frequency.

> 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.

Hmmm that would be cool :-)

Hopefully it doesn't get to that though.

Ethan O'Toole

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