How high can you up the +5v?

Hey guys. I have a Sportstation cabinet, and I just got a new power supply for it. I upped the 5v rail to just about 5.06-5.09, which I feel is a safe bet for most JAMMA games. However, the Vegas hardware itself has a molex connector onboard that powers the HDD. The 5v rail coming out of the molex connector was only about 4.7v.

I've since upped it to about 5.10-5.13, but I question whether or not I should leave it like that. This brought the 5v on the molex cable to about 4.9v, which I want to say is the best of both worlds for both rails. Would you guys agree? I just fear it may be too high for the actual JAMMA board itself.

I usually don't go past 5.15v, you can go to 5.2v but remember at 5.25v some chips start to fry.

Ah, thanks Xian. Much appreciated.

I once plugged one of my CPS2 boards into a golden tee jamma cab once to try it out and I noticed that the fan was running unusually fast. I then measured the voltage and it was outputting close to 6 volts! Needless to say, I quickly dialed that back down to 5, but nothing on the board fried.

Apparently that Golden Tee had been running a 6 volts all it's life and it never died.

I have my 6 slot dialed up a bit to 5.10v, since I know it's a bit more power hungry than other multislots. I've heard of people going to 5.20v with them, and even claiming it requires that much, but I've had no problems with 5.10v.

andy251203 said:

I once plugged one of my CPS2 boards into a golden tee jamma cab once to try it out and I noticed that the fan was running unusually fast. I then measured the voltage and it was outputting close to 6 volts! Needless to say, I quickly dialed that back down to 5, but nothing on the board fried.

Apparently that Golden Tee had been running a 6 volts all it's life and it never died.

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It could have been that the GT was drawing so much power that it was less than 6v.....

Xionicist said:

I have my 6 slot dialed up a bit to 5.10v, since I know it's a bit more power hungry than other multislots. I've heard of people going to 5.20v with them, and even claiming it requires that much, but I've had no problems with 5.10v.

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It only required that much because they had voltage drop across the board due to insufficient wiring.

You WANT your 5V at 5V...

Xionicist said:

I have my 6 slot dialed up a bit to 5.10v, since I know it's a bit more power hungry than other multislots. I've heard of people going to 5.20v with them, and even claiming it requires that much, but I've had no problems with 5.10v.

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If I got a dollar (better: euro) for every time I heard this BS...

People (noobs) should try to understand that when a board is said to be "more power hungry" it means it needs more current, not more voltage. The voltage must remain the same, i.e. 5V or very close to that (not to mention that MVS boards are absolutely not picky in this respect, i.e. they work even at a much lower voltage, like 4.6V).

Yes, TTL IC's are not too fussy about supply voltage at all. I have successfully ran some IC's on <3V. (Recommended minimum is 4.75V).

TTL, NMOS, CMOS, etc... all run from between 4.75 to 5.25 volts. If you check the data sheets for these various chips, you will find that there is an absolute maximum voltage you can run these at.

If you run below 4.75, nothing will fry. Logic level "1", a.k.a. "high" may not always be reached properly so you will end up with glitches and crashes. Going over 5.25 and you have serious risk of frying chips.

Hell, there are some risks running at 5.20v. There's suspicion that 5.20v will eventually fry the small surface mount buffer chips on the NAOMI carts. Those chips seem to be excessively sensitive to overvoltage.

There's NO reason to run your power at more than 5.2 volts. If you have a board that crashes at 5.0v then you either have a flaky chip on it OR you have insufficient power reaching the far side of the board. Some boards (Bubble Bobble, Neo Geo 4/6 slot boards) have alternate power connections to help with this. They aren't always used though.

Exactly. The main point of an arcade power supply is to deliver a regulated +5V to the board. You'd have to be a moron to adjust it to do anything other than that.

That is not completely correct, many CMOS devices can run on as high as about 18V.

Hewitson said:

That is not completely correct, many CMOS devices can run on as high as about 18V.

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I'm referring to CPUs, EPROMs, SRAMs, etc. I'm not referring to 4000 series CMOS chips. Check the datasheets and I'm not going to play the corner case game.

ideally you should check it on the board itself, on one of the ICs vcc pins. There will be some voltage dropped at the jamma edge connect.

Worst place to check is the psu as there will be drop in the harness and connector.
5 volts at the psu may be only 4.5 or even less at the board (depending on the boards current draw)