HELP: Space Encounters RAM test results and questions

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I found the following information on how to test the RAM from a Space
Invaders (or in my case a Space Encounters) motherboard PCB so I
decided to give it a try since my Space Encounters cabinet does not
work yet.

<START QUOTE>
TESTING RAM:

To fix Space Invaders family of game boards, first remove ALL the game
ROMs, then turn the game on. You should see a repeating pattern of a
thin and fat lines across the screen. Next close the Slam switch for a
moment, this pattern should change, but still be solid lines (thin or
fat doesn't matter, but they repeat). Now if any lines are flickering,
or there are dots on the screen that are sometimes covered by lines
but reappear when you "Slam" the switch, then you defiantly have RAM
problems. Next, try momentarily shorting pin #7 of each RAM chip to
ground until you find the one(pair) that when shorted either make
solid the flickering line or cover the dots. Now you just have two
suspects to replace. Sub one at a time, then alternate. It is only one
of the two Ram chips that share the pin #7 output that should be bad.

If you've got a completely blank screen with all of the ROMs removed,
then you have a more root cause of your problem than just bad RAMs.
Check your clock generation circuitry with a scope first; have you
checked the power supply yet? Also try swapping out the 8080; it
should be socketed.
<END QUOTE>


I performed the RAM test with the daughter board (ie: gameLogic PCB)
still connected ... is this correct or should I have removed the
daughter board before testing occurred?

I also verified -5V, +12V and +5V were being applied to all the chips
on the motherboard PCB, daughter board PCB and sound PCB, so I believe
my power supply is alright.

Basically, what I did was to remove all of the ROM chips and then
turned on my Space Encounters machine. The monitor looks like a
white screen with alternating thin and fat lines which seem to be
shaking or flickering. I do not have a functioning coin door (thus no
slam switch), however, I simply connected the yellow and red wires
from the molex which should be used for connecting the coin door to
simulate the slam switch being closed. I know these are the correct
colored wires to use since someone who has a Space Encounters cabinet
emailed me a photo.

Anyway, when I connected the slam switch wires, all movement (ie:
flickering) stopped on the monitor display..... everything was simply
"still". Since nothing moves on the display when the slam switch is
closed, then does this mean I have a RAM problem or not? I was
confused by the "TESTING RAM" directions (see above) in regards to
this step. I was not sure whether the flickering should stop when the
slam switch was closed or whether the flickering should start when the
slam switch is closed.

Just for the sake of proceeding to see what would happen, I decided to
continue testing the RAM chips. Just to let you know, the slam
switch was open for the next tests. I took a paperclip and touched
pin#7 on the RAM chip with one side of the paperclip and touched
pin#22 (ground) with the other side of the paper clip. I did this to
all 16 RAM chips but there was still flickering on the monitor display
no matter which RAM chip I tested.

Any ideas what is going on or what to try next? Am I doing the test
correctly? Do you think I need to replace the CPU chip?

Thanks for your input,
UncleT