Using a logic probe I found that one of the outputs on the LS283 at 7R was stuck high. Changing this IC fixed this issue! 

Hi! I have an issue with one of my DK boards. This video shows the issue. It's 100% sure it's on the video PCB and it's not a ROM or PROM issue (I've swapped boards and ROMs to make sure). So has anyone seen this before, and can guide me in the right direction?

https://www.youtube.com/watch?v=pqZ_otZzdAU

...

The issue is solved. After rechecking the ROMs I found a faulty 2716 at 7D on the video board. It's now working flawlessly! I got the hint from here:
http://www.brasington.org/arcade/tech/dk/

https://www.youtube.com/watch?v=27uSeG9soQQ

Hi!

You guys helped me fix my other DK board. Thanks for that by the way!

I've bought another DK board. This one was converted to Hero in the castle of doom. It DID work with that mod (after some minor repairs), but I wanted this DK back to it's original state. I've been burning new EPROMS and inserted a new Z80 and now the board is back to DK!  

However I'm having some sprite issues. You can see these here:
https://www.youtube.com/watch?v=wf50n5acDnA

The issue is on the video board. I have tested with another working video board and then the issues are gone. The ROMs are also ruled out. So, have any of you guys seen this before? Any tips where I should start troubleshooting?

Thanks in advance!

Hi there! Did you ever fix this issue? I have a faint background "siren" noise on my boards as well. I've read a lot about and it just seems to be some kind of "weakness" on the boards, and that you will have to live with it. But if someone find a solution it would be great.

Solution: 2 bad ECL translators, an MC10124 at 4H and the MC10125 at 4F.

That solved my issue. I changed the MC10125 at 4F and the glitches are now gone! I ordered both some 10124 and 10125, but the problem went away after the first chip I changed. So I didn't bother changing all of them. It has now been running flawlessly for about an hour and it still runs fine!

https://www.youtube.com/watch?v=lxAwUYxm0so

Thank you for leading me in the right direction!

Thanks guys! I was actually suspecting those myself. These are among the IC's on the board that gets hot, and therefore may fail after some years. I've ordered a few of both 10124 and 10125's. I'll let you know if that fixes the problem.

Hi!

I'm a long time follower of the John's Arcade youtube channel! :-) I'm located in Norway. I have built a DK cabinet from scratch and have aquired 2 DK boards from the US.

So to the problem: I'm having an issue with one of them. I have some small glitches on the screen. They seem to appear only on the left half of the screen. I have isolated the issue to the video board. I swapped the boards from my fully working one. I have also ruled out the ROMs. The PCB plays normally apart from these glitches. So does anyone know what's going on here? I have a video showing it here:
https://www.youtube.com/watch?v=ar58yV3aQag

Btw: Here's a video of my homemade DK cabinet:
https://www.youtube.com/watch?v=MUQDk4dkLts

I appreciate any help I can get. Have a nice day.

--
John Roger