3 Oct
2007
3 Oct
'07
9:28 a.m.
At 9:31 PM -0400 10/2/07, Allison wrote:
The two EPROM's in question are 27128's of different manufacturers.
The strange thing is both have the same pattern in them (I read them
in when checking). I did manage at the same time to erase a 27C128,
2 different 27C256's, and a 27256. Rather irritating as I'd prefer
to use either 27128's or 27C128's for the next step. Hopefully
either these two really are good, or the other two I have, and still
need to erase, are good. I won't be able to mess with this more
until at least tonight.
At 8:31 AM -0500 10/3/07, Phil Spanner wrote:
From:
"Zane H. Healy" <healyzh at aracnet.com>
How do you tell an over-erased EPROM?
I finally have my programmer and eraser, and just tried erasing 6
EPROM's. Four erased just fine, and two are showing weird patterns
of alternating blocks of 04/06 and 14/16.
I've seen that when the quartz window isn't really clean and the
UV hasn't quite done the full job. I have found some vendors
eproms need a little more time to cook.
Ove 26 years I think I've only seen one that really had a stuck
bit and that was a blown output pin. After erasing thousands of eproms, I have not
experienced a maximum
ttme. You can try to erase them again. I personally have left eproms
under an eraser for days, with no ill effects on the eproms.
If another tour under the eraser doesn't work, then you have two bad eproms.
Over the years, I made a living replacing defective eproms on
telecom equipment.
If they do erase, mark them, because my experience tells me they
will fail when trying to reprogram. Or they would be a good starting
point for board failure troubleshooting and repair.
One thing I've noticed is that my "dirt cheap" P.O.S. Chinese eraser
takes a lot longer than I would expect to erase chips. Here is what
I bought last week to erase EPROM's.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=140150073985
OTOH, the $50 Willem EPROM Programmer seems great so far.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=130156704118
Zane
--
| Zane H. Healy | UNIX Systems Administrator |
| healyzh at aracnet.com (primary) | OpenVMS Enthusiast |
| MONK::HEALYZH (DECnet) | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| PDP-10 Emulation and Zane's Computer Museum. |
| http://www.aracnet.com/~healyzh/ |