TMNT Jamma graphics problem

[KonamiHam]

Hi
I have recently become the proud owner of a Teenage Mutant Ninja Turtles jamma board but seem to have a problem with it.
The game plays fine, the sound is fine, the start-up test screen and test modes all show everything is ok, BUT...
The colours seem to flash brighter and darker in certain parts of the game. Most notibly, whenever the screen is scrolling during the game.
The colours also seem washed out and flickery on the title screen and hi-score screen.
The strange thing is, it is fine the rest of the time, for example in the intro, animation sequences, the attract sequence and also on the colour test screen in test mode.
I was wondering if anybody could point me in the right direction? I'm thinking I'll have to send this away for repair if I want it to work perfectly, but thought I would check for pointers here first.
I'm using the board with my own self made rig on a LCD screen through RGB scart. I know it works properly as I have 2 other very similar PCBs made by Konami: The Simpsons and Aliens, and these both work fine.

By the way, I am in the UK, and the board appears to be the UK version as it is called 'TM HERO turtles' if this makes any difference...
I think it is also the 2 player version.

Does anybody know the importance of having resistors on the R, G and B wires when using a SuperGun with scart?
I'm sure I read recently about using something like 75 Ohm resistors on the wires to get the best colours possible?

I'm just wondering if this would help?
Although it wouldn't explain why the other 2 Konami boards work and TMNT doesn't.

Thanks in advance for any help you could throw my way!

[viletim]

Yes, you'll need resistors in series with the video signals. Experement to find the best value (which may be different for each board). 100 ohms is a good start.

[Shou]

Actually, I have the same problem with my JP TMNT PCB as well on the JP equivalent of a Sony PVM. Xexex also has a similar problem. Other Konami PCBs (Gaiapolis, Mystic Warriors, GI JOE, Simpsons, X-MEN) from the same period do not exhibit this problem though.

[KonamiHam]

Interesting...
Guess it must need sending away for repair then...  I'll let you know what happens.
Have you or Xexex tried repairing your boards at all?

I soldered some 100 Ohm resistors on the video wires, but no cure

Thanks for the help though!

[ken_cinder]

There IS always the possibility of a slight variation in sync or any other signal for that matter (By design, by mistake or by a damaged component on the board).

Try your setup on a different display. If it goes away, there is a very good chance the above is true and the other display can compensate. If the same occurs, the above could still be true, but at least you'll have a better idea for sure.

At this point, I'd go over the resistors/caps on the board looking for components not doing their job properly or leaking (caps). TMNT is now a 20 year old game, it's very much possible for a cap on the board to have begun leaking just due to age.

[viletim]

KonamiHam,

My advice would be to try it on a proper arcade monitor before declaring the board faulty. Arcade boards arn't designed with domestic TV/Monitor electrical compatibility in mind.

[KonamiHam]

Ok, thanks for the advice.  I have a couple of other TV's I can try it on, unfortunately I don't have access to an arcade monitor though.

I have some circuit diagrams of the board, so I might try looking over those at the weekend.

[Shou]

Interesting...
Guess it must need sending away for repair then...  I'll let you know what happens.
Have you or Xexex tried repairing your boards at all?

I soldered some 100 Ohm resistors on the video wires, but no cure

Thanks for the help though!

Xexex as in the game, not a person....both work fine on an arcade monitor.