More Apple II fun - 4116s...

Mr Ian Primus ian_primus at
Thu Apr 30 14:36:09 CDT 2009

--- On Thu, 4/30/09, Ethan Dicks <ethan.dicks at> wrote:

> Hmm... I have so many 4164s that I'm not horrified to
> mod the chip,
> and I might have to do that if there isn't enough
> vertical clearance
> (not an issue in a PET, but might be an issue in the TRS-80
> Model
> III).

Yeah, and 4164's are pretty easy to come by. I don't worry about modifying the individual chips - but then again, I'm typically only using modified chips to replace individual failed 4116's.
> As for a socket mod, how does this sound? ...
> Take a 16-pin machined-pin socket.  Poke out pin 1 (-5V). 
> Poke out
> pin 8 (+12V).  Take another 16-pin machined-pin socket. 
> Remove pin 1
> on it as well.  Break off the pin tail from pin 8 so that
> it won't
> dangle into the socket below.  Install a jumper wire from
> the modified
> pin 8 to pin 9 (+5V).  Install that socket on top of the
> previously
> modified socket (the one with pins 1 and 8 missing). 
> Insert a 4164
> into the top socket.  Install the stack into a 4116 socket
> on the
> target board.  Repeat 7 times for a bank of 8.

Sounds like it would work perfectly. The only issue I would have with it is that the two machine pin sockets you would need cost more than the 4164's do, and you have to purchase those sockets new - whereas you can scavenge 4164's from junked XT clone boards. :)

> Good to know, but I have so many 4164s that I'm
> unlikely to use 41256s.

Yeah, and 41256's are much harder to get - I just brought it up as a just-in-case. I once spent an afternoon using a propane torch to scavenge soldered-in 41256's from scrap HP printer boards in an attempt to upgrade a Sun VME machine.

In many instances, it's actually easier to modify the board to take 4164's than it is to modify the chips or build adapters. But, again, that's not very original, and involves hacking the board. I typically only use these one at a time when necessary to replace bad chips (because I don't have any spare 4116's). I know a common modification on Wiliams arcade games like Defender or Robotron (which use piles of 4116's) is to simply replace all the chips with 4164's and modify the board (two trace cuts and one kludge wire) to take them. Or, in the case of the game, since nothing else on the board uses 12v or -5v, you can actually build an adapter for the power connector that disconnects the -5v, and routes the +5v to the +12v line - and then just plug 4164's straight in with no modification.

It really depends on your application, and how the board you're installing them in is set up. Do whatever works best for you and the particular machine you are repairing. But you can definitely, replace 4116's with 4164's with minor modifcations and expect it to work just fine.


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