GORF Repair - just died

flex

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I have a GORF which just died.
I'm hoping there's somebody that might have some insight to troubleshoot this game. I have both manuals, the original GORF and the Card Rack System to help lookup anything. I'm full of questions right now and not finding enough answers online.

I checked the power supply and all voltages are there, +5V, +12V and -5V. I even checked the +5V directly on the CPU card across the 0.1uf caps. The RESET line out of the power supply is a HI level = 5V. The schematic says this a an Active LO signal, meaning it should pulse LO to reset the processor and return back to a HI Level. But I don't see anything on the monitor screen. As far as I remember it's supposed to talk when the game is turned on, but it doesn't.

Wasn't there a website which provided some tips to troubleshoot bad problems like this in a systematic way to locate the bad card when you have several cards in a game ?

Does it really need ALL 6 cards just to bootup and display anything on the monitor ?

Is it possible to just plug in say the CPU card and RAM card to see something on the screen ?

I tried some extra card racks --untested after several years-- that I have here and they all exhibit the same thing - absolutely nothing at power on. I was hoping I would get different symptoms between them. Something that would get me started in repairing this game.
 
Did you coin up and see if its playing blind? It sounds like you have a monitor problem. You would likely get some kind of garbage on the screen at least.
 
I have a Gorf I just got running......I would agree it sounds like a monitor issue. Mine does not talk on powerup. Confirm that the monitor is working first......check for power, b+, neck glow, coin it up and c if there are any sounds? Lots of other trouble spots on these, but start there.
 
I did some checking in the meantime. Using the Card Rack System Manual, I checked the signats on the backplane. I noticed that the Processor was still running, it wasn't locked up, stuck in Reset or Halt. However without using a Logic Analyzer I couldn't tell where in the Rom Code it was stuck in a loop. So since it was basically running, I suspected that one of the Roms must be bad, so I swapped out the Rom card wiht one of my spares. It works after I tried a couple of spare Rom cards I have here. I'll have to check later which one of the Rom chips went bad.

I still have an issue with the voice. It tries to speak, but it has garbled voice during the game. One more thing to fix still.

One thing I noticed is that I have 2 different versions of Rom cards. One is part# A082-91364-A000 and the other is part# A082-91374-A000. I expect there shouldn't be a problem, probably some bug fixes in the new version.
 
I did some just other testing, to take some notes for future repairs. The Card Rack system needs only the CPU cad, Rom Card and the Game Card at minimum to bootup. The other 3 cards, Pattern Card, and the two Ram cards are not needed.

And by plugging in the Ram cards individually and the Pattern card separately, you can see the different behavior in the way the display screen is refreshed.

Of course, all you see is a raster screen with only red since the video sync is running properly. And it changes to the next screen properly, but with only a noisiey hash display since there's no background graphics available when the two Ram cards and Pattern card are unplugged.

Also, you still hear the background sounds, if you have that enabled on the Dip Switch. And it will coinup too to start a game. It's a good way to check if the game can still bootup. properly.
 
I did some checking in the meantime. Using the Card Rack System Manual, I checked the signats on the backplane. I noticed that the Processor was still running, it wasn't locked up, stuck in Reset or Halt. However without using a Logic Analyzer I couldn't tell where in the Rom Code it was stuck in a loop. So since it was basically running, I suspected that one of the Roms must be bad, so I swapped out the Rom card wiht one of my spares. It works after I tried a couple of spare Rom cards I have here. I'll have to check later which one of the Rom chips went bad.

I still have an issue with the voice. It tries to speak, but it has garbled voice during the game. One more thing to fix still.

One thing I noticed is that I have 2 different versions of Rom cards. One is part# A082-91364-A000 and the other is part# A082-91374-A000. I expect there shouldn't be a problem, probably some bug fixes in the new version.

One ROM card is "domestic".....the other is "foreign". The ROM chips between these two can not be mixed! On some of these, Midway used masked ROMs (all black, no quartz window). These always seem to have exteremly tarnished legs. They also become very brittle. Sometimes a good cleaning fixes you up.....but, sometimes the act of removing them from their IC sockets causes the legs to break off. Midway also used pretty cheap IC sockets. Your ROMs could be good....and just a bad IC socket. The 2114 RAM on the ROM board can also cause issues (bad RAM or just bad sockets).

Regarding your speech.....you could have a bad SC-01 speech chip (or a bad IC socket). Also, if I remember.....the SC-01 chip has a signal that runs through one of the custom input/output/audio chips. These are the two 40-pin chips...side by side. Swap them with each other and see if the issue changes. Once again, these could have a bad IC socket on the customs, too.

Edward
 
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