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Author Topic: Zig Zag (Dig Dug bootleg)  (Read 2885 times)
tim
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« on: November 20, 2005, 04:41:10 PM »

Symptom 1
Game goes through self test, reports RAM OK, ROM OK, then the grid. After that, it either hangs
there or resets again. Sometimes after the ROM OK, ROM OK, it also shows a bunch of input port
stats that change randomly.

Tests
Inspection of the board revealed two empty sockets. Looking closely, I could see "2114"
silkscreened under the sockets.

Fix 1
Stole a couple 2114's from a Qix board. Game boots. A little research determines that this is the
RAM for the Z80 that the bootleggers added to replace the custom I/O chip that a real Dig Dug has. That's
why the self test did not complain about this RAM being missing. It doesn't test for it because it's not supposed to exist.

Symptom 2
Game now appears to work. Hook up sound. No sound. Playing with volume pot produces scratchy, faint sound. Grinding pot
increases volume of scratchy sound, which erraticly cuts in and out. A piece falls off the pot.
Sound no longer works. Replaced pot. Still no sound.

To do
Make an audio probe to see if an audio signal is getting to/from the amp.
Logged
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