Donkey Kong 2-board black screen (dead CPU?)

mecha

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I got my wiring harness in the other day and converted my DK cab over from 4-board to 2-board and tried running the 2-board set I had laying around. I was a little disappointed that I went from one set that would randomly freeze (probably due to the standard switching PSU mod that was done on it vs. running an actual Nintendo unit) to one that doesn't even work.

it makes the startup sound, but just a black screen, which by my guesstimation means the sound chip is good and the main CPU is bad. I tested for voltage at the CPU and got nothing, and a healthy 5.09V at the sound chip.

initially the CPU wasn't even in all the way. I took it out and cleaned the corrosion off the legs and reinserted it to no avail.

didn't notice any damaged components on the boards. could the chip just be bad?

I loaded my DK3 board in there for now, pretty fun game. mysteriously the wave effect (symptomatic of high/low B+/bad filter cap etc. that I fixed/replaced) that I had in the monitor before with the 4-board DK has gone away completely. does that VR2 pot have anything to do with that?
 
If you put a DK3 board in your cab I assume you are using the edge connector since the DK3 board does not use the little connectors like DK and Junior. If that is true do you have the rainbow cable installes between the 2 boards giving the video board power? If not, that's your problem. - Barry
 
it's an edge connector now. I have both styles of DK boards, I pulled the 4-board kind. it's a 2-board now.

I believe I have the correct harness, it goes from P3 on the 2nd board side to... wherever it fits on the CPU board?

that's exactly what that looked like btw, like there was just no video. it wouldn't coin up either though.

confirm that you need that rainbow cable for the 2-board stack, before I go blowing something up. lol
 
P12 on the main board to P4 on the video board. I don't think you'll harm anything if it's not there, it just won't work. The DK3 board has one and you may be able to take it off and use it on the DK, I just don't know if it's long enough. - Barry
 
thank you sir. I was getting worried KLOV lost its touch.. it's a DK-related question after all.
 
You MUST use the rainbow cable on a 2 board stack when using the edge connector or your video board will have no power.
 
got that, just snatched the one off my DK3 for now.

I'm missing sounds now, I have the walk and jump sounds, missing music and everything else.

I looked over all the caps, didn't find any with broken legs. I'm seeing a lot of stories where people recapped the sound section and it didn't change anything. anyone have any other ideas?

btw, this board runs substantially better than the 4-board I pulled out. and thanks, now I know what this infamous rainbow cable is.
 
just out of dumb curiosity I popped the sound CPU out of the 4-board and installed it.... it didn't bring the sounds back, but it did make a BEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEP. so I said ok, time to try the 2-board chip again.

and I coined the game up and heard sound. it all worked again. now is there any particular explanation needed for this.....??? I already did the final step about 3 times with reseating the chip and that didn't take.

maybe I shouldn't ask for an explanation and just be glad I don't have to re-cap it. thanks gents. now back to Defender.
 
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