Univac panel and mystery TTL chips

[Joe R.]

At 07:46 PM 10/6/05 +0100, you wrote:
>> >Then you might be abloe to identify some pins as definite inputs (driven 
>> >from totem-pole outputs on known ICs), others as definite outputs (only 
>> >go to known inputs). 
>> >
>> >If all else fails you may have to desoler the IC, power it up on a 
>> >breadboard, find outputs with a logic probe, try the inputs, and so on.
>> 
>>    I used to have an article out of one of the electronics magazines that
>> told how to identify various pins on ICs using an ohm meter. Input pins,
>> output pins and power and ground pins all have different characteristics.
>
>Be warned that this sort of test depends critically on the particular 
>logic family, and the type of ohmmeter in use.
>
>As you hace the chip on a circuit board, you can easily find pins that 
>are tied to +5V or ground (you _must_ be able to find those 2 rails on 
>the board, if nothing else by starting from a chip you know the 
>number and pinout of). OK, there may be pins other than the Vcc and Gnd 
>pins that are connected to those points on the unknown chip (e.g. unused 
>inputs), but I think you should be able to indentify the actual power and 
>ground pins fairly easily.
>
>> Unfortunatly I lost the article. Does anyone have any info on how to go
>> about doing this?
>
>How about starting with a known IC of the family you're interested in and 
>recording the results for your meter between various combinations of the 
>pins? 
>
>> 
>>    But all in all I like Tony's Suggestion of looking for the parts with
>> dual markings and make a cross reference list. When you get done, post it
>> on the net to benefit everyone. Spere has a good start on HP and Tektronix
>> cross reference on their website.
>
>I know for a fact that some of the IC's on that HP list were indetified 
>by finding dual-marked ones on HP boards. And others were indentified by 
>finding inputs and outputs and indentifying the functions. I know this, 
>because I did it :-)

   They also got a good number of the crosses from instrument service
manuals. Unlike the calculator manuals, the instrument manuals usually gave
the HP PN, manufacturer code and manufacturer's PN. I supplied a lot of the
instrument part number listings to Sphere also some of the numbers from the
dual marked parts.

>
>There was a good HP equivalent list published _by HP_ in Bench Briefs at 
>one point.

  Bench Briefs published a series of issues with cross references. I don't
remember if each one carried a different range of PNs or if they broke them
up by equipmnet useage or what but I know the cross reference was spread
over a good number of issues. I had a fair number of BBs but never had the
whole cross reference.

   Joe


 It was half a dozen pages, 3 columns, fairly small font. I 
>haev it, but I know it wouldn't stand scanning or copying, and I don't 
>feel like typing it all in.
>
>-tony
>