aclbandit
Member
Sega System 18 (Moonwalker / Shadow Dancer) PCB problem
Been out of the hobby for half a year or more with work; finally trying to get caught up on some projects.
I've got a board repair that has me totally stumped.
Origin: a friend asked me to look at his Moonwalker because it had some graphics corruption issues. Basically a few of the sprites (for example, the children's "Help Me Michael!" text balloons) had this corruption pattern that I can best describe as "basket weaving."
So, the troubleshooting steps so far:
1) Eventually, I discovered that if I "pet" the EPR-13228 chip, the corruption wiggles (but doesn't go away).
2) Replaced all the big filter caps around the edge
3) Checked all ROMs, replaced one that only had correct data for some reads (new chip is consistent).
4) Replaced two encrypted ROMs with decrypted ROMs, replaced CPU with 'regular' CPU instead of battery-backed encrption CPU
5) Bought a Shadow Dancer PCB in desperation. Swapped stuff around between the two boards, and discovered that the issue follows the daughterboard, and has nothing whatsoever to do with the mainboard or the ROMs (both games work perfectly if ROMs are in the daughterboard from Shadow Dancer, regardless of motherboard on which the daughterboard is placed; both games exhibit the issue if their ROMs are placed in the daughterboard from Moonwalker, regardless of the motherboard on which the daughterboard is placed). The corruption issue affects Shadow Dancer in that the dog in the attract screen has the 'basketweave' pattern, and so does the control instruction sprites.
6) Reflowed solder
7) Replaced all the ROM sockets
8) Replaced the 74HC139 chip
The graphics corruption issue persists (and no additional issues encountered, so at least I haven't made it worse).
Anyone have schematics for these? Suggestions? Anything at all?
Been out of the hobby for half a year or more with work; finally trying to get caught up on some projects.
I've got a board repair that has me totally stumped.
Origin: a friend asked me to look at his Moonwalker because it had some graphics corruption issues. Basically a few of the sprites (for example, the children's "Help Me Michael!" text balloons) had this corruption pattern that I can best describe as "basket weaving."
So, the troubleshooting steps so far:
1) Eventually, I discovered that if I "pet" the EPR-13228 chip, the corruption wiggles (but doesn't go away).
2) Replaced all the big filter caps around the edge
3) Checked all ROMs, replaced one that only had correct data for some reads (new chip is consistent).
4) Replaced two encrypted ROMs with decrypted ROMs, replaced CPU with 'regular' CPU instead of battery-backed encrption CPU
5) Bought a Shadow Dancer PCB in desperation. Swapped stuff around between the two boards, and discovered that the issue follows the daughterboard, and has nothing whatsoever to do with the mainboard or the ROMs (both games work perfectly if ROMs are in the daughterboard from Shadow Dancer, regardless of motherboard on which the daughterboard is placed; both games exhibit the issue if their ROMs are placed in the daughterboard from Moonwalker, regardless of the motherboard on which the daughterboard is placed). The corruption issue affects Shadow Dancer in that the dog in the attract screen has the 'basketweave' pattern, and so does the control instruction sprites.
6) Reflowed solder
7) Replaced all the ROM sockets
8) Replaced the 74HC139 chip
The graphics corruption issue persists (and no additional issues encountered, so at least I haven't made it worse).
Anyone have schematics for these? Suggestions? Anything at all?
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