Replacement for a DEC 7474 Chip

John Robertson jrr at
Sat May 14 12:41:34 CDT 2022

On 2022/05/14 10:11 a.m., Rob Jarratt via cctalk wrote:
> Hello,
> I have found a bad DEC 7474 chip on my M7133 board. Clearly it is a
> 74<something>74 D flip flop. The problem is I don't know which modern series
> would be the best one to replace it with. I am sure I have seen a list
> somewhere of modern equivalents for some DEC chip numbers, but I can't
> remember where.
> If it helps at all, on the PDP 11/24 printset it is E78 on page K6 of the
> schematic (p157 of the PDF).
> Picture of the failed chip here:
> Can anyone tell me what the best modern equivalent is likely to be?
> Thanks
> Rob
You are stuck with using an original 7474 family assuming this is 
driving other early TTL. 74LS74, and others simply don't have the drive 
capability to work. You can use 74S74 or 74F74 as they have the same 
output current, the "S" is Schottky, and the other is "F"aster.

I find that https:/// is a reliable source of TTL.

John :-#)#

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