Genesis 2 VA1 Triple Bypass - CVBS Restore?

[NoAffinity]

I'm trying to figure out what is needed for CVBS restore with a TBP on a Genesis 2 VA1 (US/NTSC). Oddly, I get composite video from the 32X plugged into the base unit, but not from the base unit itself. That's probably a side discussion about how the 32x generates video.

Hopefully all of the below is thorough enough information for someone to deduce what's going on and why I have no composite vidoe being produced at the A/V out (mini din 9) pin for composite video. I have confirmed this with a set of simple Genesis Model 2 A/V cables (yellow/red/white), which work fine at the 32x's output but I get no video when connected to the base console's A/V out.

I completed the TBP per these instructions. My TBP is a v0.3, but the same instructions apply for basic wiring. The first link is most useful, and what I followed excatly. The others are good cross-references.

• https://github.com/zaxour/TripleBypassV ... A0-1_8.pdf
  https://www.consolesunleashed.com/guide ... all-guide/
  https://github.com/tianfeng33/triple-by ... l/VA0VA1.8

The below excerpt is from the TBP v2.0 installation instructions. What I don't know is if there are any jumpers on the v0.3 that need to be configured per the below. Nothing on the v.0.3 TBP is similarly labeled.

Spoiler

I have confirmed that my resistors are configured correclty for my VA1, and per the below.

Spoiler

Lastly, pins 21, 22 and 23 are lifted on the CXA1145, but not pin 20 (CVBS out). I have checked the circuit from pin 20 of CXA1145 to the Composite video pin of the A/V out (mini din 9), and the components are there and continuity is good from point to point.

I am curious - does the removal of all of the other components on CXA1145 pins 14-18 affect its ability to generate comoposite video? Schematic of that section linked below.

Spoiler

RGB for the TBP is sourced from the bottom of the board, and NOT from the alternate location on the top of the board. I in fact removed all the components from the top of the board cuz I thought that might be needed for CVBS restore (since it's all mentioned on the same page), but had to put them back because it killed RGB altogether. Presumable they have to be removed IF using the alternate RGB source location, but ONLY IF using that location.

[NoAffinity]

Just realized that circuitry to pins 14-18 are not populated by default. If I'm reading the below correclty, from the CXA 1145 data sheet, it seems that the existing circuitry at pins 17 and 18 needs to be in place for the CXA1145 to generate composite video.

Spoiler

So, I'm now less clear on how composite video is generated on these consoles, and how to restore it. Any input from the smart people on this forum would be greatly appreciated.

[NoAffinity]

Okay, well this thread is pointless except maybe the curiousity about the 32x generating composite video when the base console does not.

I found a scan of a Model 2 VA1, and see the pads to the right of the CXA1145 (which are associated with pins 14-18) are indeed populated.

I must've removed them when originally installing the 3BP, some years ago. Looks like I need to repopulate them to take this any further.

[NoAffinity]

Did some digging, found the 32x schema and sure enough, the 32x generates it's own composite video.

Along the way, I also wondered if, in the event that the 32x is generating it's own video output, if the 3BP even matters when you have a 32x hooked up.

The rgb input from the base console is clamped and either passed through to the 32x a/v out rgb output, or sent to the y/c circuitry which ultimately generates composite video and goes out to the 32x a/v out video out.

So, a 3BP will benefit 32x RGB output. It also appears to produce cleaner composite video, which I assume is a result of the composite video generation in a different chip than the cxa1145 or other ic's native to the base console which are usually to blame for the subpar composite video output from genesis's/md's.

So, i guess I answered all my own questions. Hopefully this personal conversation provides good info for others interested in these subjects.

[jd213]

Yeah, I found this thread pretty interesting even though I have little interest in the 32X. Need to get around to installing the TBP boards I bought into my Model 2s and my Model 1 VA7 one of these days. Wonder if I should get a 32X just to test the output.

FWIW, Zaxour was pretty responsive when I asked him a question on Ko-Fi, but I bought my boards directly from him.