4 Switch, Rev 16 Video Out Mod Issues

Grizzly Adam · June 21, 2023

Good morning,

I am currently working on modding my Vader, which has a rev 16 board. I completely removed the RF module and installed according to these instructions-- with the exception of removing Q202. I have seem at least one video where the transistor was not removed, and some claims that it's removal merely improves the signal, so I wanted to see the difference for my self. My results are not very good, please see the attached images. The screen tearing (I believe that is the right term) that can clearly be seen on the left side of harmony.jpg was present before the mod and was not addressed in case the issue was in the RF modulator-- it clearly was not. As you can see from frogger.jpg, I have no color on my 15 or so year old Phillips LCD that we keep in the family room. I wanted to include a picture of the video routed through a RCA to HDMI converter, but the signal was not strong enough to activate it.

What would be your next move? I know I should probably remove Q202 but I was hoping to hold off on that, just out of curiosity. Should I look at adjusting the values of the 2.2k and 3.3k resistors?

Grizzly Adam · June 22, 2023

I worked on this further, swapping the 2.2k and 3.3k resistors for 4.7k and 6.8k, respectively. I saw no change with the color signal, but if I flipped the B/W switch I got a strong B/W signal on Frogger. My oscilloscope showed approx .2v as the peak on the video signal before the changes, and .45v after. I tried a few more variations, but nothing improved the signal or the strength. The pre-assembled mode I chose used SMD resistors and it did not work well trying to attach full size resistors, and I ended up damaging the contacts to the point that I can no longer continue with that board (or at least I chose not to because it is beyond my skill level and frustration tolerance). I have ordered the same type of mod to replace it, but this time I got one with full sized components.

Before ruining the mod board, I did end up clipping Q202 and BOOM-- color! So now I know the effect it has on this board, and I am left wondering why some people can get away with leaving it on. I dialed in the colors using testcart and frogger and was happy with the result. I am now eagerly awaiting the new mod arriving, in the meantime I have received replacement capacitors and zener diodes to install as static arrestors, per the service manual.

+x=usr(1536) · June 22, 2023

12 minutes ago, Grizzly Adam said:

I worked on this further, swapping the 2.2k and 3.3k resistors for 4.7k and 6.8k, respectively. I saw no change with the color signal, but if I flipped the B/W switch I got a strong B/W signal on Frogger.

Jus something to bear in mind (and you may already be aware of this), but the Colour / B&W switch doesn't do anything in hardware - it's up to the software to detect the switch and go into one or the other, if supported.

Some games used it as a supplementary game control. Activision's Space Shuttle comes to mind as an example.

Grizzly Adam · June 22, 2023

24 minutes ago, x=usr(1536) said:

Jus something to bear in mind (and you may already be aware of this), but the Colour / B&W switch doesn't do anything in hardware - it's up to the software to detect the switch and go into one or the other, if supported.

Some games used it as a supplementary game control. Activision's Space Shuttle comes to mind as an example.

Yep, as a Space Shuttle fan I am very aware of that. But when I flipped the switch on Frogger, it cleaned things up and made all those vertical lines in the game disappear.