12v reading 13.9!
- Thread starter Ste72
- Start date
John Bennett
Senior Member
Is that on all games under load?
Fortunately the 12V rail is a lot less sensitive than 5V, as it's used by things like coin counters and audio amplifiers.
Is that a single wire running to all your 5V pins on the JAMMA? I run 4 5V wires and 8 ground wires from the PSU to the JAMMA header as the voltage drop was terrible for more current-drawing games, otherwise.
Fortunately the 12V rail is a lot less sensitive than 5V, as it's used by things like coin counters and audio amplifiers.
Is that a single wire running to all your 5V pins on the JAMMA? I run 4 5V wires and 8 ground wires from the PSU to the JAMMA header as the voltage drop was terrible for more current-drawing games, otherwise.
John Bennett
Senior Member
Yeah, I don't know the inner circuits of arcade SMPS's, but the 5V adjust knob does seem to move more than just the 5V, whether by design or not 
A 13.9v reading does seem rather high.
Normally, when you plug in a hungry powered board the voltage will drop a bit at the JAMMA edge (and therefore so will the readings on the voltmeters).
I test every adapter before sending them. The voltmeter readings are normally within 0.04v for 5v and 0.2v on the 12v line.
Have you got a multimeter to check/confirm the voltages?
I’m happy to replace the voltmeter or adapter if you think it’s gone faulty.
Normally, when you plug in a hungry powered board the voltage will drop a bit at the JAMMA edge (and therefore so will the readings on the voltmeters).
I test every adapter before sending them. The voltmeter readings are normally within 0.04v for 5v and 0.2v on the 12v line.
Have you got a multimeter to check/confirm the voltages?
I’m happy to replace the voltmeter or adapter if you think it’s gone faulty.
I doubt it's your adapter tbh! Yes got a voltmeter so will test with that today. Power supply issue might be most likely.
Switching power supplies with multiple voltage outputs like Arcade switchers, PC power supplies and so on often have only the main voltage regulated, the secondary voltage(s) are just tracked to the main voltage. This means, the secondary voltages are not truely regulated, they just follow the regulation of the main voltage. So a low power consumption on a secondary voltage can lead to higher voltages than expected, especially if the main voltage has high load.
If you want to regulate every single voltage, you have to use seperate regulators and seperate transformers for every output voltage or you have to stabilize the output voltage with linear regulators after the switcher. Both solutions will make the power supply much more expensive than the solution with the tracked voltages.
If you want to regulate every single voltage, you have to use seperate regulators and seperate transformers for every output voltage or you have to stabilize the output voltage with linear regulators after the switcher. Both solutions will make the power supply much more expensive than the solution with the tracked voltages.
Thanks all for your inputs. I've got two cabs and tested both across a couple of boards and overall I think the cabs power supplies are fine. The voltmeter works perfectly and shows 5v / 12v with no load now I've done some adjustments. Different boards bring the 12v to no more than 13v max now. It was a bootleg Rastan that pushed it to 13.9 but I've got that down to 13v now so happy. Thanks!