ID UV erasable PROMS used on an IBM PC board?

[dwight]

Years ago when I was at Intel, they would take EPROMs that had only a few defects and attempt to program them with specific applications. They would then usually paint the window black and put on that particular product number. When we needed EPROMs in the lab, we would take a pile of these that were no longer used and scrape the paint off the window. Some would take the desired program and some wouldn't.
I suspect that they can fuse identify specific bad EPROMs to use for such harvesting. The fused value may be laser blown as well. My guess is that that is the reason for the different ID number. If it will take pre-programming with a particular data, it is worth harvesting.
This way they can find value in an otherwise unsellable product. I doubt the harvesting methods have changed much over the years.
Dwight
________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Paul Berger via cctalk <cctalk at classiccmp.org>
Sent: Tuesday, March 22, 2022 1:14 PM
To: D. Resor via cctalk <cctalk at classiccmp.org>
Subject: Re: ID UV erasable PROMS used on an IBM PC board?

I can tell you what some of the chips are on the power supply board, but
the list I have is mostly TTL parts

1582684 LM324
1582606 74LS74      F/F D-TYPE DUAL +E/T
2392122 7417        BUF/DVR HEX O/C (TPD0 30NS)
8272147 74LS05      INV HEX O/C

Aside from the house numbering of parts which is not unique to IBM, IBM
had their own foundry for many years so you will encounter custom  parts
for which there is no industry equivalent, this is also not unique to
IBM, I have some HP computers that many of the parts are house numbered,
and HP also manufactured their own chips so there are some parts that
are unobtanium as well.

Paul.

On 2022-03-22 06:40, D. Resor via cctalk wrote:
> 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
> volts.
>
> 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
> connector.
>
> 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 hotmail.com>
> Sent: Monday, March 21, 2022 4:50 PM
> To: 'General Discussion: On-Topic and Off-Topic Posts'
> <cctalk at classiccmp.org>; D. Resor <organlists1 at sonic.net>
> 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.
> Dwight
>
>
>    _____
>
> From: cctalk <cctalk-bounces at classiccmp.org> on behalf of D. Resor via
> cctalk <cctalk at classiccmp.org>
> Sent: Sunday, March 20, 2022 6:53 PM
> To: 'General Discussion: On-Topic and Off-Topic Posts'
> <cctalk at classiccmp.org>
> 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?
>
> https://www.dropbox.com/s/f6rvemx9ldbbv5x/EPROMS1.jpg?dl=0
>
> No need for a Dropbox account, close the login pop up and you can view the
> image.
>
> Thanks
>
> Don Resor
>
>