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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

Bav
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    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. – Andrew Morton Nov 10 '20 at 15:46
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    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. – ocrdu Nov 10 '20 at 16:30
  • Can always try asking on https://e2e.ti.com/ – Tom Carpenter Nov 10 '20 at 16:34
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    Couldn't decide on which forum to ask so ... Case details: Number CS0326496, State Open. Now, we wait. – ocrdu Nov 10 '20 at 16:55
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    @Bav: TI responded; they can't find it and don't know what it is. No idea how much effort they put into trying, though. – ocrdu Nov 20 '20 at 20:56
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    @ocrdu ah well - thanks for trying! I've not seen any other TI DIP with this style of marking even... – Bav Nov 21 '20 at 21:56
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    Are these possibly old RTL (resistor transistor logic) or DTL (diode transistor logic) chips?--if so you'd need a special databook to identify them. I inherited a bunch of these in a grab bag many moons ago and cleaning them out was kind of annoying because of the non-standard markings. – Andrew Lentvorski Dec 20 '20 at 10:51
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    Possibly, although would this be likely in 1974? I'm still no nearer solving this mystery! Wondering if TI made anything else in DIL packages in that era... – Bav Dec 21 '20 at 19:07
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    RTL/DTL would absolutely still be around in 1974--certainly for a military supplier like TI. Westinghouse only cleared out their last RTL/DTL chips circa 1980. – Andrew Lentvorski Dec 21 '20 at 22:48
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    "M26"... could it be Mystery chip #26? – rdtsc Feb 26 '21 at 13:29
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    Maybe these are ASICs? If so, they wouldn't be in any data book, and the markings would have been determined by the customer. – Theodore Mar 23 '21 at 14:35
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    The only time I seen IC screen printed like this is when I was component level troubleshooting an early 80's Rockwell 8086 based computer. I think they are ram chips. – David Mikeska Apr 20 '21 at 11:00
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    If you decide to give up on *using* them, you could always ship them to [Zeptobars](https://zeptobars.com/en/) and have them turned into beautiful pictures of the chips inside. – Theodore Apr 26 '21 at 21:47
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    I wasn't aware of Zeptobars. That's another interesting website I've learned through this question, even if we're no nearer solving the mystery! – Bav May 06 '21 at 16:43

2 Answers2

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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.

SamGibson
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dougp01
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  • 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. – Bav May 06 '21 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...

rackandboneman
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