More Apple II fun - 4116s...

Ethan Dicks ethan.dicks at
Thu Apr 30 14:15:25 CDT 2009

On Thu, Apr 30, 2009 at 2:57 PM, Mr Ian Primus <ian_primus at> wrote:
> --- On Thu, 4/30/09, Ethan Dicks <ethan.dicks at> wrote:
>> Is this hack as simple as
>> eliminating the -5V and +12V to the socket...?
> Yup. That's _nearly_ all there is to it. You need to change the +12v into +5v...

Ah... that makes perfect sense.

> and disconnect the -5v entirely.


> You can modify a single chip by bending pin 8 up and folding it over and soldering it to pin 9 (may need a bit of wire), and clipping off pin 1 completely.

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

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.

I think I can find the used 4164s I removed from my DEC Professional
350 when I upgraded it to two banks of 41256s.  I think that would be
a suitable source of parts to upgrade a PET - a donation from another
classic machine.

> You can also modify the board. If you tie pin 1 of the sockets either high or low, you can also use 41256's.

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


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