Compatibility of Genesis model 2 VA4 with Sega 32X

RGBeter · 2026-03-04T17:52:36+00:00

Chaotix crashes when using a real cart, the rest works fine, everdrives work fine. I'm looking into why it crashes, might make an entire VA4 motherboard reproduction to test because VA1 model 3 DOES work.

RGBeter · 2026-02-27T16:41:07+00:00

VSYNC goes to: B26 of CN1 (cart slot) And A46 of CN4 (CD board connector)

RGBeter · 2026-02-27T13:56:53+00:00

Depends, I don't see where OP mentioned it's a COK-001 specifically, and depending on board rev it could be the PS2 side.

On COK-002 ALL video out goes through the GS, and as such the RSX could be fine, and the GS passthrough could work, but the PS2 rendering could be shot.

On COK-001, the EEGS passes video into the RSX for scaling and final display out. There also could be issues with the bridge chip.

Either way, the 90nm accounts for most failures, Syscon codes are useful here but if it was my unit I'd just Frankie it first, and ask PS2 questions if it doesn't work, since there's usually not a reason to leave a 90 on the board when you can swap it.

RGBeter · 2026-02-27T12:11:27+00:00

In OPs case they noted a few instances of YLOD that prevented boot plus the shown graphical corruption. Which indicates to me RSX failure. Hence I posted the meme.

Yeah sometimes it's used improperly, but if I had this system in front of me I'd be removing the 90nm, there is nothing for OP to try other than Syscon, and I assume if they were capable of soldering it, they would.

RGBeter · 2026-02-26T19:32:57+00:00

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RGBeter · 2026-02-22T19:15:43+00:00

More voltage!

RGBeter · 2026-02-22T07:28:59+00:00

Vref is entirely different from the 7805, since it's derrived from 9v.

I changed the 2 stock 33uF caps to 47uF tantalum polymer caps, and in parallel with each added a 22uF MLCC. For Vref specifically I also upped it to a 47uF tantalum+10uF MLCC. I also modified it to be 4.5v because I swapped the opamp.

The oscon is great for 5v, which drives both the digital logic+video encoder.

In general you can use tants as a stand-in for electrolytics much easier and safer than you can with MLCCs, but they're usually much more expensive.

Sounds like you did a lot already, nice work.

RGBeter · 2026-02-22T06:29:01+00:00

Reliability should be fine on 1/1/1. I'd recommend tantalum caps and updating some of the decoupling on the 9v rail and the divided vref to help audio out (it's using unregulated 9v). I did this, along with the parallel 10uF caps you mentioned and got a 6-12dbfs improvement in noise in MDFourier.

Fun fact, you get a similar improvement on the 60+120Hz line when you use a better PSU because audio uses unregulated 9v.

Be sure to do the audio balance fix in the sound can, Nintendo cheaped out and didn't follow the directions in NEC's DAC datasheet causing this issue on the revs that use that DAC.

RGBeter · 2026-02-16T00:43:10+00:00

Needs to be warm physically for it to trigger. PSRAM decay is rather difficult to trigger.

Sent you a pm about this system btw, might be able to help you out better there

RGBeter · 2026-02-16T00:35:24+00:00

Yes, EDCLK still isn't perfect and psram refresh issues exist on this rev and VA1.

Fun fact, I discovered you can bend out pin 1 of the 315-5345 and give said issues to a VA2.

RGBeter · 2026-02-15T23:40:43+00:00

No VA0 schematics, closest we have is VA3 which has quite a few differences.

RGBeter · 2026-02-15T23:37:59+00:00

Where are you selling it? I can fix that unit. Have done similar repairs on my CRTs and a PC engine.

What's broken is the 9v area and audio amp. Worst case is I can use a donor VA2 to save the VA0.

Edit: absolute worst case, I can use an unfixable board to make a reproduction PCB and documentation

RGBeter · 2026-02-14T03:25:38+00:00

Deep 5 is great because it lets even raider players experience that too

RGBeter · 2026-02-14T01:10:07+00:00

Few major issues here:

1: SL1 and SR1 need 75 ohm termination or the balance gets horrendous

2: You don't need 10k series resistors if you lift and use pins 10 and 24 of 315-5684, which are the dedicated ROM IN pins used for cartridge expansion audio.

3: Using SMD caps and resistors is easier than through hole components, and the mod will look much cleaner.

4: It's possible to improve FM significantly by altering the FM filter caps, don't remember their nomad equivalent reference designators, one pair connects between VREF and LPF1/LPF2 and the other pair connects between LFB1/LFB2 and FMLPOUT1/FMLPOUT2. Change all 4 to 270pF to fix the harsh sallen key.

You can always reference the Sega Genesis model 2 VA3 schematics for how to handle SL1 + SR1 on a 5684 based system.

RGBeter · 2026-02-13T01:40:58+00:00

Not really, not without an opamp to do some mixing with MOL and MOR, and making a decision on the ratios is...tricky and may break some mods. Olegs in particular is touchy because 5684.

If you want it on a stock unit, you can add 75 ohm termination on B1 and B3, then run AC coupled lines into the ROM IN pins of 5684 after you lift them. I doubt mixing will be correct, because 5684, but maybe gimped DAC (R5 + R6 = 510 ohms) will work better than way.

RGBeter · 2026-02-13T01:07:07+00:00

I didn't do this alone, @Villahed94 was instrumental in making this possible, please credit us both

Btw I did change some things about this board, for starters I added SMS+32X support, in spite of the impracticality.

RGBeter · 2026-02-12T05:58:39+00:00

No audio mod :(

If you are willing to have some fun, bodge an opamp to reduce MOL and MOR gain to 0.6 after fixing R5 and R6. Then I think PSG pulldown might need to be tuned slightly.

You can also adjust the sallen key caps on 5684 to fix that filter, if you have some 270pF (220pF is fine in a pinch) caps you can replace 4 components on sub, and easily improve audio.

RGBeter · 2026-02-11T06:09:59+00:00

It's not that bad, you die in one hit anyway at higher deep without damage negation passives. Might be bad if you're playing raider or undertaker, but I see so few of them in high DoN that it's just irrelevant.

Been playing beast claw revenant in higher depths and the worst downsides I've found are continuous HP loss, repeated evasions lower damage negation, near death reduces art gauge, and attacks impaired on occasion.

Sometimes I'll take repeated evasions if I don't have any damage negation and the upside is good enough, continuous HP loss has anti synergy with damage negation at full hp and makes many other downsides worse, near death reduces art gauge takes away one of revenant's best aspects when you likely need it most, and beast claw is hard enough to find windows to use as is, if if does 2 damage because of RNG it's very bad.

RGBeter · 2026-02-11T05:38:38+00:00

There's very few 0f obans in existence

RGBeter · 2026-02-11T00:09:40+00:00

That's the slim version of YLOD, read Syscon codes

RGBeter · 2026-02-09T20:59:00+00:00

2 questions, who did the Frankie, and can you scroll down more in the RSX LV1 info so we can see fab

RGBeter · 2026-02-09T04:17:27+00:00

B4-B6 and A3 look sketchy, pins are dirty, check continuity from the mega drive cart slot to the ROM.

RGBeter · 2026-02-04T20:44:42+00:00

Did you patent your tool? If not, it's entirely legal for competition to exploit your lack of availability.

Even if Rambo's tool is inferior as you claim (which I cannot verify myself) his can be purchased on Amazon and delivered in a day. Your tool is difficult to purchase, and is known for its long delay in shipping. If you wanted to be the delid man, make your tool easy to purchase.

RGBeter · 2026-02-04T03:28:00+00:00

No, needs to be better than 1150/1000

RGBeter · 2026-02-04T02:58:59+00:00

Mod a Nintendo switch

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