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Working on a mid-80's engine control unit, I have spent the better part of two days finding datasheets/pinouts for two mystery chips. I originally thought they were 4000 series logic chips, but no such numbers exist.

The unit is from a gen and appears to be a Ford EEC-IV controlling throttle body injection, on an accessory board labeled "FBC", for "Feedback Carburetor"

The were apparently made by Signetics (now NXP) - due to the S on the chip. However, I cannot find any datasheet for either the 4501 or 4514 part:

enter image description here enter image description here

The full markings are:

IC1: 4501 8408 S 005BB

IC3: 700002BB 8422 S 4514

I was able to determine that:

IC1 has +5V on Pin 3 & GND on pin 12

IC3 has +5V on Pin 4 & GND on pin 8

I suspect that 8408 / 8422 are date codes. IC3 smells like some sort of OpAmp with nonstandard pinout!?

For what it's worth, here are schematics I drew of the periphery around them:

enter image description here enter image description here

Any hints, however silly, are appreciated!

UPDATE After getting my hands on some high resolution images of other boards, some of them have:

IC3 = S4501 = S4017 = RCA 340; but they are all marked (70)005BB

IC1 = S4514 = S4513 = S3501; but they are all marked 700002BB

It appears that this is the "true" model number of an ASIC possibly. I have not found any cross mappings of internal part numbers to real part numbers as for the other board yet.

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  • \$\begingroup\$ 7422 , 4 input NAND gates maybe, 8 version for higher temperature range in this case \$\endgroup\$
    – user208862
    Commented Mar 12, 2021 at 18:53
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    \$\begingroup\$ The 7422 doesn't have GND on Pin12; I suspect the 8422 being a date code. \$\endgroup\$
    – namezero
    Commented Mar 12, 2021 at 18:59
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    \$\begingroup\$ It is often very useful to be able to determine which pins are ground and which one is the power supply to identify a device. Your schematic doesn't seem to give information about that. \$\endgroup\$
    – Kevin White
    Commented Mar 12, 2021 at 19:42
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    \$\begingroup\$ Most likely ASICs. Looks like a Signetics logo on there. The best way to figure out a little black box is to measure inputs and outputs and have a guess at the function. If you need to replace them, that's going to be hard. \$\endgroup\$
    – ScienceGeyser
    Commented Mar 12, 2021 at 21:40
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    \$\begingroup\$ +1 to OP - this is a great reference as to what a part identification question should look like for EE.SE. \$\endgroup\$
    – Adam Lawrence
    Commented Mar 15, 2021 at 16:08

1 Answer 1

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I believe to have identified the chips by elimination based to supply voltages, VCC and GND pins.

IC1 = LM339 or pin-compatible

IC3 = TI5534 or pin-compatbile

I have redrawn and simplified the schematics while hopefully making no mistakes and the circuits seem to become more understandable and sensible:

enter image description here enter image description here

For now, I won't accept it as answer, but wanted to provide it as potential answer. Should anything change about my assumptions, I will update the post.

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