English Mark Darts Super 6 - No Video Help

[coyote640]

English Mark Darts Super 6 6000 Series.
Doing a repair. The video on this just stopped working one day.
Monitor is good, have tried more than one. Only has 1 video jack, the extra one was never there.
When hooking an LCD to it, it finds a signal but the screen s black.
Have re-seated everything on the board, and it is working but playing blind.
I don't have an oscilloscope to check the video output of TMS9118 (U11). 
Any thoughts or suggestions? Much appreciated! Thanks.
 

[jennifer]

I have never worked on one of those, But I do have a complete one on the kill list (tentatively slated for end of Oct)...If you need parts or boards.

[Ken Layton]

I've seen the video ram chips go bad more often than the video controller.

One thing that's easy to check: if after 30 minutes of being powered on, the video controller chip (the TMS one) or the video ram chips are way too hot to the touch, then they are bad.

[coyote640]

Jennifer: Definitely interest. Thanks...

Ken: Will do that now and let you know! Thanks...

[coyote640]

Hey Ken, Only after 15 minutes I couldn't touch one of the TMS4416 Memory Chips.
I guess I better find some to order. At least it is a starting point.

FYI - I also successfully installed my second switcher PS in one of these because of your tutorial.
What happens when the Dallas Battery Chip dies in these?
Thanks again! 

[coyote640]

Progress! Changed the video ram chips and got the video back. Now on to the next issue.
With the Target Assembly is plugged into the main pcb, It just freezes on boot. Boots up fine with it unplugged.
I figure I should start by checking the Target interface board, then clean the Target assembly.

Jennifer: Let me know when you have parts available, hopefully will know what I need by the end of the weekend!

Ken: Thanks again for the help with the video issue!

[coyote640]

This machine has a Single Ribbon cable matrix (Thin Spider). Unlike the manual that show the 3 Ribbon Thick.
Does anyone have the schematic or chart to that shows how to test the Thin Single Cable Target Interface?
Thanks!

[Ken Layton]

Check the 6300 manual and the 6000 series target head info here:

https://sites.google.com/site/mtpacifico/mikes_arcade/kens_korner

Usually, if the machine locks up as soon as the target head is plugged in, that means a stuck switch in the target head matrix. Probably from stuck/broken tips in the segments or from accumulation of dirt/gunk on the rubber damper (I use lighter fluid to clean it off). Never saw any failures of the interface board. It was always dirt/broken tips or a bad switch matrix causing target head problems in my experience.

When the Dallas ram chip internal battery fails, you'll always get garbage on the screen during attract mode. You can clear the garbage out with the "Spider Writer" function, but the garbage will come back as soon as you turn the machine off/on again. Remember, those chips only were rated for 10 years memory retention.

Glad the video rams fixed the problem with the video signal. About 20 years ago, Jameco was having a closeout sale on those chips for like 25 cents each. So since we had 100 English Mark Darts machines on the route, he bought 200 of those chips.

[coyote640]

Thanks for all the info Ken! 
Took the target head completely apart over the weekend and cleaned everything as suggested and removed all broken tips.
Long and tedious task! The lighter fluid worked great! Removed and wiped down every segment too.
The head only had 2 of the 8 screws holding it together, so those were replaced.
In the condition it was in, I am surprised it worked before at all!
Everything is now WORKING as it should on the bench!
Thank you! Thank you! Thank you! 

Just have to reassemble and we should be golden! 

[coyote640]

Working as it should now. Thanks for all of your input!