8250LP problem

From: Nicolas Welte (welte_at_chemie.uni-konstanz.de)
Date: 2000-10-11 21:25:35


someone sent me a 8250LP for repair, and I'm somewhat confused with this
device. This device is equipped with Speeddos ROM replacements
(seemingly having 2k instead of 1k Controller ROM, on a special RIOT
adaptor board that also puts the CPU onto the adaptor), but that
shouldn't matter. Before I fixed that adaptor board, the drive reported
five blink codes (Controller failure, 6502 or 6530), and now it reports
just one blink code (zeropage, 6532 failure). But both 6532 are good, as
well as both CPUs. The ROMs also should be good, I put in known good
ROMs but the blink code remains. So which other components can cause
this blink code? I'd also like to know if it is true that the drive
processes blink codes from the end, because it reverts to five blink
codes as soon as I remove the controller CPU or RIOT. This would mean
that there's only this one problem left.

I'm pretty clueless now, I'd start trying to replace the LS157
multiplexers, and maybe some stuff like LS04 and LS42 that addresses the

Once the drive is working again, I'm very interested what effect that
Speeddos has. (Yes, I'm going to upload it then). Maybe a PET Speeddos
is also needed, but I'm pretty sure I also got the ROM dumps of that
somewhere. Now I only need a PET to install them :-)

Thanks, Nicolas

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