Information about an unknown IC

[Brent Hilpert]

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.