On 2022-Feb-24, at 11:32 AM, Paul Berger via cctalk wrote: > On 2022-02-24 14:16, Brent Hilpert via cctalk wrote: >> On 2022-Feb-24, at 8:29 AM, Clemar Folly via cctalk wrote: >>> I'm looking for information about Texas Instruments TB-759933 IC. >>> >>> Does anyone have the datasheet or any other information about this IC? >> >> A search shows this question was posted over here, with a picture: >> >> https://atariage.com/forums/topic/331769-unknown-cart-ic-please-i-need-some-help/ >> >> It looks like a home-made board for a plug-in ROM expansion for >> we-are-not-told. >> The "TB 759933" is 14-pin DIP, dated coded 7226, has a house number of "239 >> 2100", but it's on a board with a 27256 from 1985. >> It looks like somebody hacked up this board with on-hand parts. >> >> 60 seconds of reverse-enginerring from the limited view in the picture >> suggests it's likely involved in the address decoding to select the on-board >> EPROM. The 759933 interconnects with a 74LS10. The LS10 appears to have >> connections to the chip-select and output-enable of the 27256 EPROM. >> >> TB 759933 is not a standard TI number but TI sometimes identified parts they >> were second-sourcing by embedding the original number in an expanded number. >> >> So a guess is this is a 933 DTL dual 4-input (AND function) expander, being >> used not-strictly-correctly to drive a TTL input. >> >> The 933 should be basically 2*4 diodes. >> >> A complete reverse-engineering of this trivial board would likely explain >> the overall intended function.
> 2392100 Look like an IBM house number for a 7400 quad NAND > > Paul. Glad you said that, I wondered whether that might be IBM, but I'm not very familiar with their numbers and don't have a xref. 7400 makes some sense with the board: pins 1&2 and 4&5 are blobbed together, i.e. acting as inverters; and the interconnections with the LS10 as far as can be seen appear to then make sense as outputs-inputs.