Space Invaders Part II PCB – Player 1 only white, no grayscale

[alfa75]

Hi everyone,

I’m currently working on a Taito Space Invaders Part II PCB and ran into a video issue that I hope someone here might recognize.

The problem is related to the grayscale/color output when using the adapter. For Player 1, all shades appear only in white — there are no grayscale levels, and therefore no proper color representation either. However, when switching to Player 2, everything appears correctly with proper grayscale and colors.

So in summary:

• Player 1: only white (no grayscale, no color)
• Player 2: normal image with correct grayscale/colors

Visually it almost looks like the intensity levels are missing for Player 1.

The PCB itself appears to have had previous repair work done on it, so it’s possible something in the video or intensity circuitry was modified earlier.

Has anyone encountered something similar on this board or on other Taito black & white / color-converted boards?
Could this be related to:

• the intensity resistor ladder / DAC
• a faulty TTL in the video mixing section
• an issue with the adapter wiring
• or something in the player-select video path

Any ideas on where to start probing would be greatly appreciated.

Thanks!

 

[Ape Cosplay]

We're missing information here. SI part II is a black & white game with a colour overlay applied on the tube. What colour mod have you done to it? Any link?

[EDIT]
My bad, I found there was a colour version too.

 

[alfa75]

We're missing information here. SI part II is a black & white game with a colour overlay applied on the tube. What colour mod have you done to it? Any link?

It also makes a difference in B/W mode. Even without the colour overlay, you can clearly see the grayscale shades on Player 2.

The adapter I’m using is the one from Corrado Tomaselli, and it supports both colour and B/W operation. Because of that, the adapter itself shouldn’t be responsible for the issue.

 

[Ape Cosplay]

Oh I see there was a colour version from Taito with different PROMs. TIL.

It is indeed very strange it's based on the player, but for that reason I'd say that's some broken logic somewhere.

Is the board set for upright or table?
From what I read the colours are simply generated from the H and V signals, so I guess the issue you're experiencing could happen in table mode since the signals are inverted (in turn inverting the image).

 

[alfa75]

Oh I see there was a colour version from Taito with different PROMs. TIL.

It is indeed very strange it's based on the player, but for that reason I'd say that's some broken logic somewhere.

Is the board set for upright or table?
From what I read the colours are simply generated from the H and V signals, so I guess the issue you're experiencing could happen in table mode since the signals are inverted (in turn inverting the image).

It’s actually not a real colour version. The adapter interprets the different grayscale levels as colours. For Player 1 they all appear completely white, while for Player 2 they show up in different shades of gray.

It also looks like something on the graphics board was modified (the blue wires), so I’m hoping someone might recognize what was done there and why I’m getting this issue.