Gorf graphics issue

Gump79

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My Gorf decided to take a crap on me. I had it playing in the garage and when I came out the voice just kept repeating and the graphics were garbled. I pulled the rack and found a buch of the prom legs looked corroded. When I was pulling them out the legs were falling off so I ended up burning a set of ROMS and replacing the bad sockets. The same problem occured. I burnt a ROM to check the DRAM and SRAM and both test good. I rechecked all voltages from the power supply and they are dead on. Any ideas? Bad Pattern Board?

 
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My Gorf decided to take a crap on me. I had it playing in the garage and when I came out the voice just kept repeating and the graphics were garbled. I pulled the rack and found a buch of the prom legs looked corroded. When I was pulling them out the legs were falling off so I ended up burning a set of ROMS and replacing the bad sockets. The same problem occured. I burnt a ROM to check the DRAM and SRAM and both test good. I rechecked all voltages from the power supply and they are dead on. Any ideas? Bad Pattern Board?


Try switching the 2 smaller RAM boards around and see if the pattern changes. They might just need to be reseated in the cage but it could also be the pattern board. That's why its nice to have a extra set of working boards so you can swap them around and find the bad board.
 
It was a few years ago but I remember now I had a bad pattern board and I found the screen shots of the problem. Mine looks worse than yours but similar.
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I did swap ram boards and it stayed the same. Anybody out there have any experience repairing the pattern boards? Going to order a logic probe but, where do I start?
 
Cold solder joint and other maladies

Looking at the image, it looks like you have a cold solder joint on one of legs of a chip, or corrosion in the socket.

Where is the game at? (e.g., basement, sun room, garage?) High humidity can wreck havoc on the old chip legs and sockets, which seem to corrode if you look at them wrong.

If you have the patience, I'd suggest using an ohmmeter on an unplugged board, and go from the top of each chip leg to the trace, on the lowest reading ohm setting (generally, 1 ohm) that you can read. If you find a high leg, you may have found the culprit.

You can also try pressing on the tops of the chips, in case one of your chips is delaminating due to age, and the leg has gone intermittent to the interior. Pressing on the top of each chip while either having a friend watch the display for changes, or using a mirror so you can see them yourself, can help you to identify the errant device.

It gets more complicated from there.

Be careful with a logic clip, if you buy one. If you accidentally put it across a regulator, you'll let the smoke out toot sweet, and really have problems.
 
issue fixed?

you ever fix the issue?
what was the fix?
 
pattern boards are disposable. There may be some masochists that will fix these, but Id rather have those goofy ear guage holes then try to fix one again.
 
Sometimes its easier to just shotgun the pattern board. There's not *that* many parts on it, and it doesn't take that long to replace them all.
 
what is shotgunning?

So I guess I'm not very slick. I'm just learning...what does shotgunning mean?

I have a similar garbled screen. I have partial sound (speech side / right side of speaker)

My biggest biff is the garbled screen. I swapped a couple ram cards and pattern cards without success, but who knows if those ram cards / pattern card actually work. I need to verify at some point.

I did however run the game without the pattern board to see what it would do...it does the same thing...repeats speech over and over, occasionally I hear other sounds.

I need to figure out how to measure the resistors and caps on the boards. I have a new meter and I put it on cap setting. The smaller caps on the ram cards were around 12-13 on the meter, though sometimes they wouldn't read. The ones on the top don't read anything. I'm not sure what they are for or if I'm even measuring them right.

Ugh
I wondered if this guy from the post ever fixed his issue. It looked very similar to mine.
 
So I guess I'm not very slick. I'm just learning...what does shotgunning mean?

When we refer to "shotgunning" a board or area, we mean to replace everything there (kind of like blasting the problem with a shotgun). The idea is you will replace the defective part without knowing which one it was but it will be fixed all the same.

Sometimes the extra money spent on replacing all of the parts is worth the time you will save by not doing extended troubleshooting.

Brian.
 
i'm mental

I guess i'm just mental and want to know what is broken. I assume even if I get a working board, i'll be wondering...what was wrong...

I don't know how to determine if a resistor, cap or diode is bad...or how to determine if a chip is bad. :)

All my voltage is good...checked that today.
 
In this case without KNOWING the pattern board is the problem, shotgunning involves replacing up to 43 14 pin sockets:

Then populating them with
(2) MC14068B
(12)MC14516B
(4)74LS257N
(2)MC14572UB
(1)MC14555B
(2)74LS175
(6)MC14175B
(1)74LS161N
(2)74LS367
(2)MC14008B
(2)74LS04
(1)74LS00
(1)MC14174B
(1)74LS74
(1)74LS157
(1)MC14013B
(1)MC14081B
(1)F 45398 (7905)
And that doesn't even cover the resistor list.

So yea, take that list and then attempt to run equivalents. There's not THAT many components right? Running a shotgun on this would be foolish without even knowing in fact that the pattern board is at fault.
 
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