Tech: more space invaders goodness.

Archived from groups: rec.games.video.arcade.collecting (More info?)

> On boot, things look good, and it goes to that garbled test pattern. after
> that, there appears to be a few blinking graphics (thin lines) at the top
> right of the screen, that are stationary. nothing else happens.

That's not a test pattern - it's just garbage. Space Invaders doesn't
have a built-in self-test.

> I removed the two game roms, and the thin and thick vertical test lines
> appear without a problem.

Although Midway tried to assign some meaning to those "test" lines, what
you are seeing is effectively meaningless.

> Does this mean my game roms are toast? or could there be something else I'm
> not seeing. Voltages to all IC's look good, and as far as I can see, things
> look good with a logic probe on most everything.

Possibly it's one or more ROMs, but there are still about a dozen other things that
could cause what you've described. It sounds like you're going to need more
sophisticated test equipment at this point. At least an EPROM programmer to
figure out if your ROMs are the problem or not. One hint I can offer - the Midway
documentation regarding the strapping of the boards for different ROM configurations
is misleading, so don't trust it any farther than you can throw it.

Alex
----
ayeckley@elektronforge.com
www.elektronforge.com

Archived from groups: rec.games.video.arcade.collecting (More info?)

> The symptoms you describe are typical of a PS thats lost -5 volts or
> +12 as the processor and associated TTL circuits try to run on the +5
> but critical voltages are missing from the RAM/ROMS and you *did* say
> you were working on two supplies missing voltages. Your not using these
> same supplies to test the boards are you?

I was having issues with the PS boards, but I'm using a proven supply for
testing purposes on the bench. All voltages have been checked at the edge
connector, and I'm getting plenty of juice now on all rails.

I'm about to swap chips with another board to see if that changes things.
The game seems like it wants to go, and I really haven't found anyhting out
of the ordinary, any loose connections, or any bad caps on this one.

Archived from groups: rec.games.video.arcade.collecting (More info?)

I appreciate all the help you guys have been. I really enjoy working on
this, but I have the feeling at least one of these boards might get sent for
repair. After swapping out parts between the two boards I have (both are
deluxe) here's where I'm at:

Both sound boards appear to be good as far as I can tell.

Both EPROM's do the same thing in the semi functioning board. to me this
seems like a good sign for them.

Both strapings are identical on each board, and appear original. The EPROMs
appear that way too.

One logic board shows good voltage on my test supply. I'm getting +5.1,
+13, -6 at all test points. This is the logic board that shows the flashing
lines in the upper *left* (I miss located before) corner of the screen. It
boots to the garbage, and then stays on the flashing screen. If I take the
tilt switch off ground it does freeze, which to me would say that things are
kind of working. I have +5 volts at all ICs, and no broken lines or bad
solder joints. I'm going to start a chip by chip examination for proper
operation next. seems tedious, but hey, I'm learning. I also have an EPROM
reader on order.

The other logic board does NOT boot, and does have a voltage drain whether
the sound board is attached or not. I end up with .9v on the 5 v line.
Haven't gone to far with that board yet.

That's about it. If anyone can offer any more suggestions, please do. If
not, I'll still post progress for anyone following this.






"Tony Tumminaro" <TonyTumminaro@comcast.net> wrote in message
news:a7SdnR-rII8i5XPfRVn-tA@comcast.com...
>> The symptoms you describe are typical of a PS thats lost -5 volts or
>> +12 as the processor and associated TTL circuits try to run on the +5
>> but critical voltages are missing from the RAM/ROMS and you *did* say
>> you were working on two supplies missing voltages. Your not using these
>> same supplies to test the boards are you?
>
> I was having issues with the PS boards, but I'm using a proven supply for
> testing purposes on the bench. All voltages have been checked at the edge
> connector, and I'm getting plenty of juice now on all rails.
>
> I'm about to swap chips with another board to see if that changes things.
> The game seems like it wants to go, and I really haven't found anyhting
> out of the ordinary, any loose connections, or any bad caps on this one.
>
>
>