Re: Did my Apple iiGS Die?

[Delfs <eeastman@gmail.com>]

> Yes. Can anyone suggest which component to replace? Ic, capacitor, resistor? I'm handy with a soldering iron but don't know which component to replace. I posted pictures of the motherboard earlier in the thread.

OK cant find my schematics, so I looked online.  Thanks to
ReactiveMicro :)
http://www.downloads.reactivemicro.com/Public/Apple%20II%20Items/Hardware/IIgs/Schematic/

Long and short is that I only see the Rom3 schematic, and all I have
for reference is the Rom1 main board to eyeball.  No worries though,
I've studied both boards and schematics on both for years trying to
overcome the speed bottleneck and they are virtually identical except
for the address lines on the ROM 3, it has more memory.

Back to what you need to know.  Chip UE9 next to the game socket
connector is what actually does the button signal to the data bus.  It
is a 74HCT251 chip with inputs and outputs.
http://www.datasheetcatalog.org/datasheet/philips/74HC_HCT251_CNV_2.pdf

The following points are the same electronically:
Open Apple/Paddle 0 = Game Connector pin 7 & Game socket 16 pin DIP 2
& ADB chip Pin 39 & Chip UE9 Pin 2
Closed Apple/Paddle 1 = Game Connector pin 1 & Game socket 16 pin DIP
3 & ADB chip Pin 40 & Chip UE9 Pin 3
All of these points should be high logically (5Volts or so) unless it
is being pulled low by the press of a button on the joystick or
keyboard or the ADB controller chip. (Apple Desktop Bus chip is a
keyboard/mouse interface chip.)

TROUBLESHOOT IT:
I would like you to plug in the empty (naked) IIgs main board to power
only, /nothing else/.  Then take a volt meter to pins 2 then 3 of the
UE9 chip.  Are they high or low?

They should be high on both 2 and 3.  If they are Low (about zero
volts) then something is drawing it low, either a short on back 9 pin
port or the 16 pin dip socket for the game controller, or the ADB chip
may be bad.

If the signals are high, then it is most likely the 74HCT251 chip at
EU9.

Plug in a joystick or keyboard and press the Open Apple button/ Button
0 a few times and see if the voltage changes on that line. Then try
the closed Apple button/ Button 1