🚀 go-pugleaf

kent@wonderhog.eng.ufl.edu (Kent Phelps) writes:

>OK - here is the info you guys asked for.  To upgrade the Zenith 1 Meg card
>to a 4 Meg card do the following steps:

>		1) remove all the 256k memory chips
>		2) remove the memory chip sockets VERY CAREFULLY.
>		3) remove the solder from the holes for the 18 pin
>                   sockets ( the 18 pin holes are offset to the left )
>		4) install the 18 pin sockets
>		5) change U464 from a 444-558 to a 444-529
>		6) change U470 from a 444-559 (or a 444-670) to a 444-530
>		7) move R405 to R404
>		8) move R406 to R407
>		9) remove R410
>		10) 33 ohm resistors should be added at R14, R15, and R16
>		11) install the 1 Meg DIP chips

>Suffice it to say this modification is not for the light at heart.  Removing
>36 16-pin sockets and clearing the holes for 36 18 pin sockets should only
>be attempted by someone who is very familiar with proper soldering techniques.
>The 444-529 and the 444-530 can be purchased from ZDS and I assume any ZDS
>dealer.  You might even be able to get them from Heath.

This sounds very close to what I had done, but not exactly (and my system DOES
work and runs OS/2 2.0 fine) The minor difference is that rather than "adding"
the resistors in step 10, I moved them from their existing sites to the new
ones mentioned (or at least I presume Kent got the numbers right). So steps
7,8,9 follow correctly (by my method), except the resistor removed in 9) is
moved to another spot on the board, and I added no new resistors.

If there is sufficient interest, I can unearth the written instructions used
for my board. 

Note also that this, or a similar method, was published in the Zenith Users
Group magazine a little over a year ago. I can also get that reference out (I
think I know where it is). 

Kent is absolutely right, this operation is physically quite tricky. Removing
the dram sockets from the board is NOT easy. My board was damaged by using
brute force rather than finesse, and it took a while (along with knowing the
pin-outs for the drams) in order to put the patch wires on the back of the
board to make up for broken traces on the front! The board is multi-layer, and
it's quite easy to damage the traces.

--
chad
price@helios.unl.edu
cprice@molecular.unmc.edu