Missing capacitor on a MV-1A

[Mishran]

I recently won an MV-1A board on eBay for $17.50 that had a Backup RAM error. Two jumper wires later, I got a working board! It looks like someone ran a sharp object along the bottom of the board and severed two of the traces.

Anyway, back on topic... I also noticed that a surface mounted capacitor is missing on the underside of the board that is marked PC32. Could a regular type of cap be soldered in its place? If so, how would I know what farad value to use since it isn't marked? Would I need to factor polarity into it?

The reason I'm asking is (I haven't tried a cart in it yet) at the cross hatch screen the image "wobbles" slightly. At the top of the screen the hatch bends slightly to the right completely cut from the top line. If that makes any sense. I'm bad at explaining things. If a pic would help with my description I can post one.

Thanks in advance.

 

[Xian Xi]

It's just a bypass cap so it should be 0.1uf. You can use a regular cap if you want.

 

[Mishran]

I couldn't find a 0.1uf cap in my stash, so a tried a .22uf temporarily and it didn't make a difference with the display issue anyway. Back to the drawing board I guess. Thanks alot for the response though.

 

[Born Full Grown]

The cap missing wont stop it working, i wouldnt go without it though.

 

[Mishran]

This is what the cross hatch screen looks like.

If you look at the white bars throughout the middle, you can see where they "shift" from the wobble. At the top of the screen is the bend to the right.

Inserted games give the same effect, just more noticable. I haven't found any other severed traces on the board, the caps all look good, and no corrosion anywhere. Anyone have any ideas? I'm stumped.

 

[Born Full Grown]

Yep, try another display for starters, hard to say if thatll be it or not, but that being a digital display was never designed to take a 15kHz 240p signal.

 

[Mishran]

My other boards show up fine on that display. Only the 1A gives that problem.

It's a 19" tv with VGA input. I hook my supergun to it all the time and the image quality is pretty good. I use a VGA converter with it.

 

[Born Full Grown]

Yep, its good to rule out all possibilities when diagnosing an issue, unless someone comes along and knows exactly what it is. Til then, try these simple things, no matter how trivial they may seem to you, cause it could be one of them, and they are easy to try.

After that, follow the sync back from the edge connector and see what parts it goes through and look at testing them.

 

[Mishran]

Stupid me for not trying this earlier, *sigh* but I plugged it into my cab and it had none of those screen issues. It would seem the board just dislikes my supergun setup for some reason. Regardless, I got me a good working board for cheap with just a little leg work on my part. I'm thrilled! Oh and it's a 1AX, not a 1A... its got the BIOS soldered on. Thanks for the time and responses guys, much appreciated as usual!

 

[Xian Xi]

It's not the supergun, the TV just doesn't like the signal.

 

[Mishran]

Perhaps, but why just that board? My two 1FS, two 1FZ, and 4 slot all work with the supergun on that very same TV and without issue. Even my Hyper 64 works without issue.

 

[Born Full Grown]

Different board, different set of problems

 

[Mishran]

Yeah, but more like finicky little bastard...