Posted By
Hans
on 2012-07-15
15:36:51
|  Re: Getting a pair of 1551s
Hi Richard,
It's many years ago since I looked into the bowel of a 1551. From your report I assume that the faulty chip in question is socketed and not soldered to the board directly?
So my humble guess is that somebody has been playing around with it and probably made a mistake during erasing and/or burning. If I remember correctly, not all of the homemade eprom burners for the Plus/4 did provide a correct / stable burning voltage (wasn't it 21 VDC like as for the 27256 type? Can't remember exactly).
At any rate, it's naughty to have remarked the chip from "OK" (yellow) to "BAD" (black) but not to indicate this on the clad.
Isn't that very, very Ebay-like?:
"...unit powers up and the pilot lits... can't test it further...".
Regards,
Hans.
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