Help fixing a faulty Sega Jamma I/O interface (rev. A)

Whats up everyone,

I've been working all weekend hooking up my world series baseball control panel, and have it working 95%. The HVolume pot on the player 2 analogue stick is the only one giving me problems. I tested out the pot, and its working just fine, and my wiring traces out fine with a multimeter as well.

I've isolated the problem to my I/O board. Unfortunately there is a short somewhere on it, and I'm not sure where. Pin 10 of the analogue port (where P2 HVolume goes) is getting crossed with ground. When I received the I/O, one of the fuses on the backside (right by the mask rom's socket) was cracked clear in 1/2 (only 1/2 was still on the PCB). I didn't think anything of it as the I/O functioned as it should. I'm not begining to think that the broken fuse is the source of my problems. I just removed what was left of the snapped fuse. Here's a picture for clarification:



My question is, can that fuse be the source of my problems, or is it possible that something else is at fault? Nothing else is effected except pin 10 is crossed with ground, I already tested all of the other analogue port's pins with my multi meter.

Someone please help
-Bill

If pin 10 is shorted then you simply need to trace the lines back to the components and check them. There's probably a diode, cap, resistor, and a chip in the line there somewhere... One of them will be shorted. Doubt it will be a resistor. Diodes, chips, and caps are your culprits for that.

Oh, and that part you showed wasn't a fuse, it was a coil. If it were a fuse, it would be labled with an F and not an L.

RJ

channelmaniac said:

If pin 10 is shorted then you simply need to trace the lines back to the components and check them. There's probably a diode, cap, resistor, and a chip in the line there somewhere... One of them will be shorted. Doubt it will be a resistor. Diodes, chips, and caps are your culprits for that.

Oh, and that part you showed wasn't a fuse, it was a coil. If it were a fuse, it would be labled with an F and not an L.

RJ

Click to expand...

The part I removed was a flat rectangular component, marked with what appears to be "20". It was black and very thin.

About tracing the pin down to the components... do you have tips for that? Am I checking simply for continuity with my multimeter? I'm a noob when it comes to higher level trouble shooting of arcade equipment.

-Bill