I was going through some of my random circuit boards and their schematics and came across one that said it used a 74HC154. I am somewhat familiar with these chips and was accustomed to their "wide package" design. As I looked at the circuit board, I noticed that there weren't any chips that resembled a 74HC154. There was an EPROM and some SRAM, but nothing else close to the size of the 74HC154. I checked the schematic to see which chip was supposed to be the 74HC154, which was U11. I then found U11 on the board. The silkscreen claimed that it was in fact a 74HC154, but it was just a typical width chip, not a wide chip. I did an internet search and found that they did in fact make a 74HC154 in a thinner width design. Great and wonderful; the mystery is solved, right? Not exactly. The chip itself is not labeled 74HC154 at all. I will take a picture of this tomorrow and upload it (if I remember), but until then, this is what the chip says:

(Motorola "M" with a circle around it) 4767635 XE
A24410 8544 DK

I've tried searching the top line and bottom line and neither of them yield any legitimate results. Is this some kind of custom chip? Is it programmable? Does anyone know anything whatsoever about it? I assume it has identical pinout as a "real" 74HC154, but neither my Chinese EPROM programmer or Chinese IC tester are able to test 74HC154, so I can't verify this, but I'm very intrigued to see if anyone knows anything.

 

Could be a house marked part. I have hundreds of parts that have HP part numbers and, aside from the ones manufactured by HP, all were relabeled by the original manufacturer. HP has a cross reference back to the manufacturer part number, with a caveat that the part may have had special testing and using the generic part should only be a short term fix until an HP part can be obtained.

 

Could be a house marked part. I have hundreds of parts that have HP part numbers and, aside from the ones manufactured by HP, all were relabeled by the original manufacturer. HP has a cross reference back to the manufacturer part number, with a caveat that the part may have had special testing and using the generic part should only be a short term fix until an HP part can be obtained.

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Hmm maybe so, but don't you think I'd at least be able to find some sort of reference to the part number listed on the chip itself?

 

Hmm maybe so, but don't you think I'd at least be able to find some sort of reference to the part number listed on the chip itself?

No. The manufacturer relabels the part with the house number for the customer. In the case of HP parts, there is no remnant of the original part number.

 

No. The manufacturer relabels the part with the house number for the customer. In the case of HP parts, there is no remnant of the original part number.

Oh ok, I think I get it now. Interesting. Guess that (probably) solves that mystery. Thanks!