Bubble Bobble color query

Solder

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I have an original Taito Bubble Bobble boardset wired up to my test rig and while it works okay the color gradations don't appear to be all there - all sprite colors appear to be 'washed out' (blue especially) and if I go into test mode and look at the test color pattern there is only one color gradation on the far right side, when there should be four color gradations in total.

So, top to bottom it's:

Red
Green
Blue
White

Then from left to right on each color it should get darker in three more steps for each colour (with white turning a darker shade of grey).

Is this likely to be a problem with my monitor (which works just fine on all of my other assorted boards)?

The color resistors on the board are rated at 75 ohms as they should be.

Or should I be looking for a logic problem on the video board?

Thanks
 
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Unlikely to be a monitor problem if other games work fine. This definitely sounds like something that could be in the color output section of your BB PCBs.

I have no experience with BB, but if it is like other games, there is/are color PROM(s) with a resistor ladder to give you different levels of color. If the PROMs or the logic feeding them has a problem, it could cause the symptoms you are seeing.
 
Thanks.

There doesn't appear to be a color PROM (just a PROM for video timings) or a resistor ladder (each colour has a dedicated custom SIL). All colors are washed out, but blue seems the worst.

I should also say that adjusting the brightness or contrast on my (Sony) monitor doesn't resolve the problem - it was of course the first thing that I tried. :)

A bootleg Bobble Bobble boardset works fine, but I can't help noticing that it uses 20 ohm resistors just before the RGB is finally output to the connector, where original Bubble Bobbles use 75 ohm resistors. That could of course be down to the bootlegs also using resistor ladders on the video board instead of the three custom SILs.
 
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Problem solved!

Replaced the three 75 ohm resistors (locations R3, R4 and R5 on the CPU board) with 330 ohm resistors and the color gradations are now perfect.

Looks like my monitor wasn't happy with the values supplied to it when using 75 ohm resistors.
 
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Problem solved!

Replaced the three 75 ohm resistors (locations R3, R4 and R5 on the CPU board) with 330 ohm resistors and the color gradations are now perfect.

Looks like my monitor wasn't happy with the values supplied to it when using 75 ohm resistors.

How did you arrive at this solution?
 
Educated guess, based on experience and reading about similar issues with game boards on some monitors. As for the resistor values, I experimented. :)
 
I'm going to try this today as well. Mine is washed out, too.

When I flip dip 3 on bank A and switch the board on, I don't see anything but a gray block that takes up the lower half of the screen. Am I doing it wrong?
 
I'm going to try this today as well. Mine is washed out, too.

When I flip dip 3 on bank A and switch the board on, I don't see anything but a gray block that takes up the lower half of the screen. Am I doing it wrong?

I'm trying to remember exactly, but if you have DIP 3 set to ON you also need to set DIP 1 to either ON or OFF - I forget which.

Experiment a little and you've get there. :)
 
I'm trying to remember exactly, but if you have DIP 3 set to ON you also need to set DIP 1 to either ON or OFF - I forget which.

Experiment a little and you've get there. :)

Do you by chance know which are the program roms as well? I have the 44pin version dual board. I want to change it to a USA version 2.
 
Thanks Solder, 330ohm was PERFECT. I thought I was going nuts when I first got the board since a lot of the patterns on the background weren't showing, even the lines on the eggs weren't there and the bubbles even looked weird.

Funny thing on my test game with the new resistors I had a really cool game with amazing charms from the get go. Level 1 pearl necklace, Level 2 Water Cross, Level 3 Fire Cross and Level 4 had the baby rattle bonus stage thing and level 5 had an umbrella. I had 100K score at level 4 so I got an extra life and an extend.
 
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