What purpose does 12v serve in JVS I/O board?

[winteriscoming]

I recently purchased a cheap type 1 i/o board that had a badly burnt up 12v input header. I was happy to discover it works fine without 12v. I had assumed I'd be missing out on lamp outputs, but never tested.

Today, in my OR2SP cab that has a fully working type 1, I noticed I didn't have the 12v plugged in and lamp outputs still worked fine.

What does the 12v do on these boards, and why did Sega bother to wire it up in OR2SP if it wasn't needed for anything?

 

[RealMFnG]

I read on the shoryuken forums that the Naomi if just running carts only, can do so just fine with 5vdc. Once you add in a GDROM, Dimms, NetDimms, you need the other power requirements.

 

[twistedsymphony]

I recently purchased a cheap type 1 i/o board that had a badly burnt up 12v input header. I was happy to discover it works fine without 12v. I had assumed I'd be missing out on lamp outputs, but never tested.

Today, in my OR2SP cab that has a fully working type 1, I noticed I didn't have the 12v plugged in and lamp outputs still worked fine.

What does the 12v do on these boards, and why did Sega bother to wire it up in OR2SP if it wasn't needed for anything?

I don't believe the I/O board needs 12V itself but it IS passed through to the 60 pin header. Some games might use it for lamps, others might not. I believe some coin meters use 12V.

Given that it's burnt up on your board it was obviously used for some game somewhere.

I read on the shoryuken forums that the Naomi if just running carts only, can do so just fine with 5vdc. Once you add in a GDROM, Dimms, NetDimms, you need the other power requirements.

he's not talking about 12V going to the NAOMI, he's talking about the 12V header on the JVS I/O board. noted by CN1 and CN2 here:

 

[Derick2k]

12V header on the JVS I/O board. noted by CN1 and CN2. I don't believe the I/O board needs 12V itself but it IS passed through to the 60 pin header.

Exactly that. The 12V is a sort of pasthru on most JVS boards if not all.

The only thing I can think off is if the JVS board has additional circuitry that needs to use 12v like some type of CMOS chips or some type of audio amp circuitry, etc. That's is why they say never connect power to those connectors if your jamma edge connector is already supplying power to the board.

 

[TylerDurden67]

I read on the shoryuken forums that the Naomi if just running carts only, can do so just fine with 5vdc. Once you add in a GDROM, Dimms, NetDimms, you need the other power requirements.

12v is always needed.and 3.3v too!
If no 12v,for example, how your fan and audio circuit will run?

 

[cruzlink2]

probably need 12v for motors also, like force feedback ect ..

 

[twistedsymphony]

probably need 12v for motors also, like force feedback ect ..

FFB motors typically run on completely separate power supplies, usually 24V. they require way more power than could be passed through the I/O board, you'd burn up the traces if you tried to power something like a steering wheel motor through the I/O

 

[cruzlink2]

so it's there just for fans and such?

 

[winteriscoming]

so it's there just for fans and such?

Maybe from the 12v going directly into the motherboard would go to internal fans, but not from the I/O board. I believe fans installed in the cabinet are AC.

Other than the mention of maybe a 12v coin meter, I'm not seeing much point for 12v going to the I/O board. What else would take advantage of a pass-through 12v that couldn't just get it with its own power connector straight from the PSU?

 

[twistedsymphony]

so it's there just for fans and such?

Maybe from the 12v going directly into the motherboard would go to internal fans, but not from the I/O board. I believe fans installed in the cabinet are AC.
Other than the mention of maybe a 12v coin meter, I'm not seeing much point for 12v going to the I/O board. What else would take advantage of a pass-through 12v that couldn't just get it with its own power connector straight from the PSU?

keep in mind that these I/O boards were designed to be universal with support for just about any game. Chances are they didn't have a specific use in mind when they added the 12V pass-through, just that some game at some time might need to make use of it.

while it's true anything that needed 12V could have tapped the PSU that would also require making a special harness just for that game, where as the pass-through means that 12V is already available in I/O harness if needed.