Tech: Defender Ram Failure. yeah, I know, this one is different

[Pat D.]

Was going to try to sell my game to a fellow collector. Pull it out of the
dust and fire it up. Get a "Initial Tests indicate Ram Failure" message.
Hmm I say. I'll just go into the self-test to find the bad RAM.

Power off and reboot. Watching the LEDs, I get a flash of all 4 and then 2
and 4 stay lit. Nothing else. Same error message on screen. Try to enter
diagnostics but it will only go to step one, the coin counter mode. (This is
where it is different. I haven't been able to find this problem listed
anywhere on Google.) I cannot advance thorugh any of the diagnostics.
During one of the power ups, I see the coin chute counter lists coins as
2222 instead of 0000 but that is the only difference I have noted. I change
the batteries, clean the battery holder connections and still no help.

Am I correct in thinking that I need a good set of working batteries in
order to enter the diagnostics portion of the self-test? Could it be that
the battery holder is not supplying the correct voltage to to the board to
allow me to enter the diagnostic mode?

Here is what I tried after the batteries in this order:

1.. Replaced all RAM with 4116s from BigDog and still no help.

2. Swapped out a different ROM board (ROM conditions unknown) with the same
results.

3. Installed Bob Roberts switcher to rule out bad power even though all
three LEDs are lit.

4. Checked all voltages to all ram chips and they are all correct. (-4.9)
(+5.02) (+12.02).

Is it possible that I somehow fried the replacement ram chips by using the
old power supply before switching to the Bob Robert's switcher?

I haven't checked the old power supply output voltages as I have removed
them from the system. I guess I could see if they are way out of line and
possibly fried the replacements.

If I am missing something obvious here, would somebody please hit me with
the "clue" hammer so that I can get this gem out of here?

Thanks

Pat D.

[Chris Osborn]

In article <1Mk7d.54015$He1.7554@attbi_s01>,

Pat D. <patd...@NOSPAMcomcast.net> wrote:
>I cannot advance thorugh any of the diagnostics.

>3. Installed Bob Roberts switcher to rule out bad power even though all
>three LEDs are lit.

Did you run the ground wire from the coin door buttons to the ground
on your power supply? It runs through a different connector than the
one that plugs into the ROM board.

--
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Coming soon: An arcade cabinet made of K'nex!

[Derek J. Stutsman]

Pat, have you:

- Reflowed the solder points on the connecting pins (all boards?)
- Checked/replaced the ribbon cable between boards?

Good luck,

D

[Pat D.]

No, that was next. I just didn't want to pull all the boards if it was an
"easy" fix.

I don't have a replacement cable except for the one connected to the other
ROM board. Those things are a mother to take off without breaking the tab
on the connector. Looks like Bob Roberts is getting another order from me.

I will check the coin door ground also.

Pat D.

"Derek J. Stutsman" <dereks...@gmail.com> wrote in message
news:xIKdnajaMch...@comcast.com...