pcb jamma voltage

[parts]

So I have this nifty led 5v voltage display for jamma PCBs and when ever I slide in a capcom pcb like varth or 19xx it displays a low 4.1 voltage. All my other 10 jamma games will give me 5.6 etc. Is it really that important to dial up and down the 5v Nac voltage and tweak it to 5v?

[rolins]

So I have this nifty led 5v voltage display for jamma PCBs and when ever I slide in a capcom pcb like varth or 19xx it displays a low 4.1 voltage. All my other 10 jamma games will give me 5.6 etc. Is it really that important to dial up and down the 5v Nac voltage and tweak it to 5v?

5.6V is very high. Is that the voltage measured at the jamma edge connector?

At the jamma edge the 5V coming in should be around 4.9V to 5.1V. Check with your multimeter to be sure. If its not then you should adjust the voltage on your power supply.

[parts]

Thanks for the reply. I meant to say most of my jamma boards read 5.06 (not 5.6), so capcom pcbs's are a volt lower on display.

[system11]

That's a hell of a voltage drop - actually more than I'd expect and there's a chance your power supply is low quality. Not broken, just not very good. You should eliminate the thing in the middle and check with a meter instead. Having some games use more than others is normal - for example Cave games are at the lowest power draw end of the scale, and old monster PCB sets like Senjyo are incredibly greedy.

By the way, having multiple adapters stacked together like that is a really bad idea - you get a voltage drop across each connection, and the closer to the power supply you measure, the more inaccurate the reading. If you're seeing 4.1v at that thing in the middle, you're definitely getting less at the PCB.

[RGB]

Before you jump the gun and buy a new PSU, I suggest you also check the voltage drop on the harness. Just measure the voltage at the PSU. If it's considerably higher than at the PCB side, just add two thick wires for the GND and +5V lines and do your measurements again.

[kebrank]

I have been using my Sigma Super Gun over the years with hundreds of pcbs and never had an issue. However, the voltage at the end of the harness is 5.22 V. When i plugged in a Raiden DX board the voltage at the jamma connector was 5.1 V and at 5.09 V at one of the chips. Then I connected and original Cadillacs and Dinosaurs and got 5.0 V at the jamma connector. The general idea is that you should get 5.0 V at the jamma connector or one of the chips if possible. On the other hand, I don't see any Supergun or cab user checking the voltage every time a new Jamma board is connected. My question is, would be safer to run Raiden DX at 5.0 V and Cadillacs and Dinosaurs at 4.9 V (it runs at that voltage) or 5.1 V for Raiden DX and Cadillacs and Dinosaurs at 5.0 V. The rest of PCBs should run between these values.
Thanks,
\o/.k.

[Artemio]

Running at less than 5.0 only has the risk of the game not running. Running it higher increases the risk of components failing. I suggest having it as low and close to 5 as possible.

[cools]

On the other hand, I don't see any Supergun or cab user checking the voltage every time a new Jamma board is connected.

I know a few people that do. They don't treat a cab like a console and swap games every half an hour. I even know one (just one, admittedly) that wears an antistatic wrist strap and antistatic gloves as well.

Personally I don't have many older boards that need a lot of juice - I've tested the voltage drop on everything I keep and know that it works fine with the PSU set to 5V on the smaller boards, the bigger ones drop to 4.8/4.9 and still run okay. If I'm going to swap out an old one I always reduce the voltage prior to removal so I don't get accidents plugging something in when the PSU is likely to feed it 5.9V.

[system11]

Adjust it so the lowest draw game you own reads 5.06 on the PCB, and leave it alone unless something demands more.

[kebrank]

Running at less than 5.0 only has the risk of the game not running. Running it higher increases the risk of components failing. I suggest having it as low and close to 5 as possible.

I read that under voltage is also not good but I'm not sure of that. I could run 5.1 v measured at the end of the jamma harness. This would give me between 5 and 4.9 volts for pretty much any pcb. I know major part of arcade operators were not measuring any voltage when a new game was put in. I'm not saying this was a good idea but it proves that PCBs are not that fragile. Probably anything between 4.9v and 5.1v should be perfectly fine.

Thanks,
\o/.k.

[kebrank]

Adjust it so the lowest draw game you own reads 5.06 on the PCB, and leave it alone unless something demands more.

That makes sense. This should be the perfect setting. Thanks for the tip.

\o/.k.

[jepjepjep]

Is it a bad idea to raise or lower the voltage while the board is running?

[trap15]

I doubt it'd be good for it

My money is on "you probably shouldn't do that".

[Ed Oscuro]

I don't see why that'd be a problem, so long as you aren't stupid and bump it up / down to something dangerously past spec. Dunno what standard adjustment practice is, but if you try to adjust the voltage with the unit off, you run the worse risk of adjusting it to deliver a component-killing overvoltage (and undervoltage isn't good either). If you do measure with the board disconnected, measure again immediately after power is turned on.

I think that it makes sense to calibrate the voltage just once, off the PSU. I have heard tell that many old boards get "accustomed" to running at different voltages, so while 5V is the standard in the spec, what it's actually been running on could determine smoother operation (granted I have no way of telling if such stories are influenced by people running off poor power supplies and misinterpreting the results). If it's getting 5V at the connector then probably (hopefully, who knows how good PSUs were "back in the day?") that's what it was designed for, so measurements that show a drop could be misleading, I'd think.

[system11]

Is it a bad idea to raise or lower the voltage while the board is running?

Don't do it unless you have a high turns pot on a test rig with a constant voltage readaout you can see at the time.