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I inherited three of these Texas Instruments vintage ICs, marked N286 (regular size) and M26 (unusually large). The smaller pairs of digits on the right hand side, 74 and 18, are, I assume, the manufacturing date. Does anyone have any info on what these are?

I assume the date code is 18th week of 1974. They are in a standard 16 pin plastic DIP. I can't find any information about them, and the format of the marking isn't one I've come across before: enter image description here

The underside is more than normally verbose too, marked E175A2M, in case that is of any help: enter image description here

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    \$\begingroup\$ In case anyone wonders if it's a 7418, that's a dual 4-input NAND gate with Schmitt-trigger inputs - in a 14-pin package. \$\endgroup\$
    – Andrew Morton
    Commented Nov 10, 2020 at 15:46
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    \$\begingroup\$ Can't stand not knowing what it is. I wonder if TI would answer if I opened a case with my TI account and asked them. \$\endgroup\$
    – ocrdu
    Commented Nov 10, 2020 at 16:30
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    \$\begingroup\$ Couldn't decide on which forum to ask so ... Case details: Number CS0326496, State Open. Now, we wait. \$\endgroup\$
    – ocrdu
    Commented Nov 10, 2020 at 16:55
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    \$\begingroup\$ @ocrdu ah well - thanks for trying! I've not seen any other TI DIP with this style of marking even... \$\endgroup\$
    – Bav
    Commented Nov 21, 2020 at 21:56
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    \$\begingroup\$ If you decide to give up on using them, you could always ship them to Zeptobars and have them turned into beautiful pictures of the chips inside. \$\endgroup\$
    – Theodore
    Commented Apr 26, 2021 at 21:47

2 Answers 2

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I know this request is getting a bit old and on the chance you have not found your data yet, I have a couple of resources for you to check out.

First is the bitsavers TI section on archive.org. They have a number of vintage data books in searchable PDF. I used to have several of these books in cellulose but now rely mainly on these PDF when working with vintage devices

Second, you can try going directly to the TI sub folder on http://www.bitsavers.org/pdf/

Good luck.

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  • \$\begingroup\$ Thanks Doug, those are both good resources. I am still no nearer solving the mystery. I'll have a dig into the books and see what I unearth. \$\endgroup\$
    – Bav
    Commented May 6, 2021 at 16:37
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This kind of overprinting might indicate a programmable and programmed device, eg a PROM or PAL. Since a programmable device from 1974 that has no UV window is very likely going to be a one time programmable device, it is likely useless except as a spare part for the equipment it was programmed for....

Source: Similarly looking parts I found in equipment I was scrapping for parts, which however had the original part number still visible in addition. Which showed them as PROMs/PALs/PLAs...

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