ID UV erasable PROMS used on an IBM PC board?

D. Resor organlists1 at
Tue Mar 22 04:40:34 CDT 2022

There are a few other problems.
The power supply does not power up.  Three of it's four voltages are missing
(+5vdc, +8.5vdc, +13vdc).  With no connections to the power supply board,
the +5vdc measures 4.92vdc while the other two voltages are still zero
The second issue I found upon removing the driver and processor board is
moisture had entered the typewriter's electronics and the connector between
the two boards has corrosion on many of the pins and on the PWB near the
I do not have access to a microscope.
I know it has been explained to me elsewhere that UV exposure from
florescent lamps can erase the proms.  The way I understand is the glass of
the florescent lamp filters out any UV radiation (as does the piece of glass
mounted in front of quartz halogen lighting).  In order that a UV lamp can
operate correctly the tube must be made of quartz, not glass.
Am I wrong here?  
Don Resor
From: dwight <dkelvey at> 
Sent: Monday, March 21, 2022 4:50 PM
To: 'General Discussion: On-Topic and Off-Topic Posts'
<cctalk at>; D. Resor <organlists1 at>
Subject: Re: ID UV erasable PROMS used on an IBM PC board?
The dies look to have consistent wire bonding. That would mean they are one
of the standard EPROMs made by Intel, just preprogrammed by Intel before
shipping. The numbers wouldn't be intel numbers they would be IBMs inventory
numbers. My guess is that they are 2732s. You might use a microscope and
look at the edges of the dies. They often have the die type in the metal
layers around the edge some place. Avoid using florescent ring lights as a
large amount of UVC leaks from these. White LED are or incandescent lights.
Also power it up and note which pins look to have signals. if any of the
lines have what looks like a constant voltage measure it to the nearest .01
volts if you can. That will help determine if it is driven by a signal or a
hard tied wire. Lower left and upper right should be ground and power pins.

From: cctalk <cctalk-bounces at> on behalf of D. Resor via
cctalk <cctalk at>
Sent: Sunday, March 20, 2022 6:53 PM
To: 'General Discussion: On-Topic and Off-Topic Posts'
<cctalk at>
Subject: ID UV erasable PROMS used on an IBM PC board? 
I cannot find a datasheet by any of the numbers silkscreened on these ICs.
Could these be proprietary IBM P/N numbers?
No need for a Dropbox account, close the login pop up and you can view the
Don Resor

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