Re: 8250LP - fault, how to fix?

From: Adrian Vickers (
Date: 2002-02-13 20:58:58

Thanks to everyone for the suggestions, etc.

I've just tried chip-swapping most of the pluggable ICs - one at a time - 
with a board I've got for an 8250 (regular, not LP). Unfortunately, most of 
what I assume are version numbers are different, so how accurate a test 
this is I've not been able to determine.

Anyway, the end result is zilch: The drive still reports "Zero Page" on 
powerup, regardless of whether it's connected to anything or not.

It may be time to get the oscilloscope out & have a poke around looking for 
dodgy logical highs/lows where there should be waveforms, etc., does anyone 
have any suggestions as to what chips/pins I should be paying particular 
attention to, and what patterns I should see? I ask because I'm very much 
at the bottom of the learning curve regarding that kind of electronics.

Also, there are several "unique" chips on this 8250LP (i.e. which don't 
appear on the straight 8250). These are marked:

251166-01 (UV erasable eprom)
251165-01 (UV erasable eprom)
251167-01 (EEPROM? No UV window, but similar package to above two)

There's also one on the 6530 daughterboard marked 251474-01B (also EEPROM?).

Does anyone know what these are, and whether a failure in one of those 
might cause the zero page fault?

Thanks again!
Cheers, Ade.
Be where it's at, B-Racing!

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