Re: Setup of the Apple 2 16K memory card - anyone know??

[Rubywand <rubywand@swbell.net>]

CuteGirl writes ...
> 
> Hello there,
> 
> I have an apple II with a 16k card. The card used to work ONLY after
> being in the computer for an hour or so (to warm up?!) and now does
> not work at all. There is a variable resistor ('pot') on the top that
> can be moved 1/2 turn, labled VR1. Is there any setup for this card
> with this or other parts? I have a full lab available with 'scope, but
> have no idea where to begin, and just maybe there is some instructions
> outthere. Otherwise, maybe I can find someone with one to sell in the
> Toronto area
 ....

     Your 16k 'Language Card' sounds like it may be an early model. I do not know
what the  "VR1" pot near the top is for. (If the card includes a voltage regulator
IC, like a 7805 or 79xx-- may look like a small power transistor-- the pot may be
for adjusting an on-board voltage.)

     The one hour delay you mention could, as you suggest, be for 'warming up' an
IC with a temperature-related flaw. (Some early IIgs's have a similar problem with
an ADB IC.)


     The most likely source of problems is gunking or corrosion of IC pins. One or
more of the IC's on the board are making poor contact with socket pins. The delay
could reflect the time needed to 'pump up' the charge on a some chip's pin through
a very high resistance in order to reach a satisfactory voltage-- like to reach a
'logic 1' on a high impedance input.

     With power OFF, disconnect the cable and pull the board. First, wipe/blow
away any dust and clean the board's contacts with an alcohol wipe. Next, scootch
up and resocket each IC in a socket. The idea is to have the socket contacts
scrape gunk/corrosion away and reestablish good contact with chip pins. 

     Reinsert the board in Slot 0, reconnect the cable, and turn ON the computer.
The above procedure often fixes problems on a Slot card; so, there is a decent
chance that the board will work.


     Another possibility is that you have a bad connection on one of the lines in
the cable which runs from the board to a RAM socket on the motherboard. This does
not seem very likely; but, if the above fix does not work, you could check
continuity for each line from plug pin to board.


     I don't know what the VR1 pot does. If nothing else works, you can always try
marking the pot's position, giving it a squirt of Control Cleaner, and then
diddling it back and forth. Set the pot to its original position and give the
board a try. (If the board still does not work, you might consider pulling and
replacing the pot.)



Rubywand