I received a copy of Mega Man 2 all the way from Italy yesterday. Should be some good fun when I shove it in the console and turn it on. The catch is, it looked like an Atari 2600 game when running!
While it plays fine, the music is fine etc., the graphic tiles seem to only be loading at a quarter of their actual size, but still stretched to fit the 8x8 tiles (see photos; apologies for the 1MB file sizes, they are straight from the camera). The PCB does have some corrosion but there seem to be no bad traces or solder joints, and the pins are spotless. Any pointers on what could be causing this weird graphical glitch? It doesn't go away when moving the cartridge around either (I have tried this in two NES consoles, and all of my other games work, including my first copy of Mega Man 2).
When the game is powered on for the first time, the graphics is garbled; resetting the console, letting it run the attract loop by itself or hitting Start and going to the stage select screen makes the graphics clean.
U1 PRG: NEC UPD23C2013ACZ-W03
U2 CHR-RAM: Hyundai HY6264P-10LL
PCB: NES-SGROM-04
Would a bad RAM chip cause this or is it a bad address/data line? I'm really hoping that the game ROM isn't toast, as it would be good to have this game restored.
And for those interested, it does have a cap on the board; a tiny 22uF/6.3V Panasonic CE (85°C). When tested it returned 28uF/2.2Ω. Positive goes to pin 1 of the Hyundai RAM chip, negative goes to ground (pin 72 of the NES connector).
Earlier this year (or was it late last year?), I successfully repaired two Sega Mega Drive (aka Genesis) cartridges, both games would refuse to boot due to high ohms (I think it was) on one of the pins, leaving the games dead and a black screen on the TV. Adding a resistor between the offending pin and ground fixed this problem and the games now work perfectly.
Multimeter Diode Test
I have just checked the game ROM with the same "diode test" as with the Sega games (put positive lead on GND, negative on every other pin), and all pins besides ground (pin 16) are roughly 600-700 ohms, with the exception of pins 30-32, which are tied together and 445 ohms. I'm hoping this means the ROM chip is fine, as the two Sega games were open (showed a 1 on the multimeter) on the one pin where they needed a resistor.
Testing the RAM chip returned the same result: no open-circuit or weird numbers besides 0 (GND) or 445.
Testing the CIC chip (aka 10NES), pins 6 and 7 are open. Pin 6 goes to pin 71 on the NES connector; pin 7 goes to pin 70. The game boots on an NES, so it can't be the CIC or else the console would keep flashing on and off.
Testing the MMC1 chip, pins 15, 17, 20, 21 and 23 are open. There is also a small mark on the top of the chip right above pin 15.
Testing the 72-pin NES connector, pins 14, 29, 38, 41, 50, 57/58 (NC; joined), 64, 70 and 71 of the NES connector were all open.
While it plays fine, the music is fine etc., the graphic tiles seem to only be loading at a quarter of their actual size, but still stretched to fit the 8x8 tiles (see photos; apologies for the 1MB file sizes, they are straight from the camera). The PCB does have some corrosion but there seem to be no bad traces or solder joints, and the pins are spotless. Any pointers on what could be causing this weird graphical glitch? It doesn't go away when moving the cartridge around either (I have tried this in two NES consoles, and all of my other games work, including my first copy of Mega Man 2).
When the game is powered on for the first time, the graphics is garbled; resetting the console, letting it run the attract loop by itself or hitting Start and going to the stage select screen makes the graphics clean.
U1 PRG: NEC UPD23C2013ACZ-W03
U2 CHR-RAM: Hyundai HY6264P-10LL
PCB: NES-SGROM-04
Would a bad RAM chip cause this or is it a bad address/data line? I'm really hoping that the game ROM isn't toast, as it would be good to have this game restored.
And for those interested, it does have a cap on the board; a tiny 22uF/6.3V Panasonic CE (85°C). When tested it returned 28uF/2.2Ω. Positive goes to pin 1 of the Hyundai RAM chip, negative goes to ground (pin 72 of the NES connector).
Earlier this year (or was it late last year?), I successfully repaired two Sega Mega Drive (aka Genesis) cartridges, both games would refuse to boot due to high ohms (I think it was) on one of the pins, leaving the games dead and a black screen on the TV. Adding a resistor between the offending pin and ground fixed this problem and the games now work perfectly.
Multimeter Diode Test
I have just checked the game ROM with the same "diode test" as with the Sega games (put positive lead on GND, negative on every other pin), and all pins besides ground (pin 16) are roughly 600-700 ohms, with the exception of pins 30-32, which are tied together and 445 ohms. I'm hoping this means the ROM chip is fine, as the two Sega games were open (showed a 1 on the multimeter) on the one pin where they needed a resistor.
Testing the RAM chip returned the same result: no open-circuit or weird numbers besides 0 (GND) or 445.
Testing the CIC chip (aka 10NES), pins 6 and 7 are open. Pin 6 goes to pin 71 on the NES connector; pin 7 goes to pin 70. The game boots on an NES, so it can't be the CIC or else the console would keep flashing on and off.
Testing the MMC1 chip, pins 15, 17, 20, 21 and 23 are open. There is also a small mark on the top of the chip right above pin 15.
Testing the 72-pin NES connector, pins 14, 29, 38, 41, 50, 57/58 (NC; joined), 64, 70 and 71 of the NES connector were all open.
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