Game voltages--is this normal?

[R3LL1K]

Why would anyone want to replace a proper adjustable arcade power supply with a computer one?

Hmm, maybe because the computer power supply is designed and able to handle a much larger draw than most switching power supplies. If you have a beefier power supply it can supply the voltages required without a drop in voltage. How many HDD,s optical drives, case fans, cpu fans and other items is your PC PSU currently powering and how many items is your properly adjustable arcade power supply powering?

I believe the issue Demogo is having at the moment is with his voltages dropping. What bright idea might you have to offer as a solution to the issues he's having? Crank up the voltage?

 

[modessitt]

I believe the issue Demogo is having at the moment is with his voltages dropping. What bright idea might you have to offer as a solution to the issues he's having? Crank up the voltage?

Quit using a multi-JAMMA switcher and just swap boards in one at a time when you want to play one...

 

[demogo]

OK, I've fooled with this off and on for the last month.

Voltage coming from the p/s molex is really constant over about 6-7 readings, always around 5.18. No problems with the p/s obviously, especially since it's already been replaced (for no reason, I guess).

Readings looked like this for 6 measurements:

5.18 5.19 5.18 5.18 5.18 5.18 (voltage from p/s molex across all readings)
5.09 5.10 5.06 5.10 5.10 5.07 (measured at jamma connector across all readings)
5.09 5.07 5.01 x.xx 5.04 5.02 (far end of jam extens harness; x.xx = i didn't measure result)
4.97 4.96 4.92 4.96 4.94 4.91 (reading from rom chip on pcb)

Most of the time the voltage at the rom was quite steady around 4.97; I only measured the other voltages when the rom voltage moved around which wasn't very often.

Now the interesting thing is that the voltages would jump all over when i squeezed the jamma extension harness into the jamma connector. And they'd jump around when I'd probe the jamma pins with my DMM leads or move the jamma extension cable around a bit. And the values will jump around when I hold the harness and wires down so it won't move but push on the power wires with my finger.

Some of the jumps were kind of disturbing; when I probed the wires and move them around slightly I saw variations at the rom from around 5v down to about 4.8 (it moved as I pushed on it).

I just pulled the jamma extension harness off and hit the male end (plugs into the jamma cab connector) with Deoxit and Deoxit gold. I got some grime off the cable when I cleaned it and it seemed to perhaps help a bit with the numbers jumping.

After cleaning and trying to isolate things so I was only pushing on one thing at a time I was getting jumps of around .08 when I pushed on wires.

I'm pretty sure this is the source of my jumpy voltages even though the numbers would also move around a bit by themselves even when not pushed (see the table above). Not sure what more I can do on the Jamma extension harness side so this weekend I'll re-do the +5 and ground wires from the connector from the p/s into the jamma plug with new 18ga wires and .084 and jamma split pins.

The numbers clearly move when I push on the wires/harness connector and that's likely what was behind the voltage changes when I switched games as it surely changed the tension on the wires a little. But the voltage would move around by itself even when I hadn't switched anything. The $1,000,000 question is if the jumpy voltages when not changing cables is from the same thing as when I press on the wires?

 

[demogo]

OK, I think I found an issue. I'm not sure it's THE issue but it certainly could be.

Tonight I started repinning the jamma harness connector with fresh wire and pins on both sides. I started with the red +5v wires and re-did all 4 of them and then peered inside the jamma connector and noticed that the new split pins really stuck out a fair amount farther than the ones that I'd pulled out and most all of the other ones.

I plugged it in, let it rip and the game came up and stays right around 5.00 volts (fluctuating very very slightly) at the rom even when I move the jamma cable around, probe the pins with my DMM leads, squeeze the connectors, and move the power wires around pretty dramatically with my fingers.

Before the replacement surgery my power level would jump around as much as .2 volts when I did this, now I maybe get a .01 or .02 movement even when I'm really pushing the wires around.

So I'm guessing it may have been not very good contact with the split pins on the +5v fingers that was the root of the issue.

Of course this is way premature; only time will tell if the voltage fluctuations while a game is going are fixed but this sure looks promising!