Help with Donkey Kong cabinet

[naujoks]

I bought a Donkey Kong cabinet, that's been converted to jamma, with a 60 in 1 board.
The original DK PCB is still in place, and I'd like to get it to work again.
The original monitor has been replaced by a different one, the seller told me its a NOS 19" arcade monitor. It works well with the 60 in 1 and has a beautiful bright and clear picture.
I learned that due to the new monitor there will be no sound with the original DK board, as the original monitor had the sound amplifier built in, so I would need to install an extra bit of circuitry for sound.

When I put the jamma connector from the 60 in 1 onto the DK board, I was able to make out some picture, but turning the knobs on the monitor, I was not able to get a clear picture, there was lots of distortion, rolling etc.

My question is if this new monitor in theory should be able to display the picture alright, so could it be that I need to tweak the knobs some more, or of course there might be a fault on the DK board.
What would be my next step in fault finding?

[Ken Layton]

The original DK board is NOT JAMMA. You'd need to get a DK-to-JAMMA adapter board.

Also, the original DK boards produce "INVERTED" video and don't work on standard monitors. The original SANYO and SHARP monitors which were built special for Nintendo accepted inverted video signals.

[naujoks]

Thank you, it's a bit of a learning curve for me, I'm completely new to this.
I imagined that the previous owner soldered his own JAMMA connection, that's why there's cables directly soldered to the finger connectors on the DK board leading to another finger board, which can be plugged into the JAMMA harness.
Judging from the distorted picture off the original DK board I could see that the picture has the right orientation though, so perhaps the monitor does the inversion?

[behrmr]

Your pics aren't very helpful and can't make out monitor type.  Post up some pics of the internals as well as the 60-1 board you had in there so we can see what your settings are.  You may have a VGA monitor which won't work with a DK board. Again hard to tell from the pics you posted.

But, assuming you do have a standard res. raster monitor.  And assuming you have a DK two board stack.  And assuming your cabinet is currently wired standard JAMMA:  then all you need is Mike's arcade Nintendo to JAMMA adapter.  That will invert the video, provide the sound amp, and be JAMMA.

[PL1]

Judging from the distorted picture off the original DK board I could see that the picture has the right orientation though, so perhaps the monitor does the inversion?

Inverted video "flips" the voltages on the R, G, and B lines which changes the colors, but not the orientation of the picture.
- With normal video a higher voltage on the R, G, or B line = more of that color. (brighter)
- With inverted video a higher voltage on the R, G, or B line = less of that color. (dimmer)

Most PCBs send a normal video signal that will work with either a normal monitor like yours or a video inverter (normal video in ==> inverted video out) + an inverted-video monitor like the original Sanyo.

Some PCBs like DK send an inverted video signal that will work with either an inverted-video monitor like the original Sanyo or a video inverter (inverted video in ==> normal video out) + a normal monitor like yours.

There's a great description of video inversion on this page at Mike's Arcade.   


Scott

[naujoks]

Mike said that my DK board has the inverter built in (and sound amp).
He thinks the pots on the board might be kaputt, so I'll swap them and see if that fixes the picture.
Still no sound though, and the dropped coins don't get recognised so I still can't start a game, but I'll check if everything is alright with the cabling.