J-Pac and Power Supply loading

[Dave_K.]

According to the ultimarc website, the j-pac does not require a power supply, in fact they recommend you remove/disable it.  As per the FAQ:

But my JAMMA cabinet DOES have a power supply.

Most cabinet power supplies will not function unless a game board is connected, owing to insufficient load. It is best to remove the power supply completely as the J-PAC does not need any power. All power comes from the keyboard or USB interface. The monitor power must be left as it is though. DO NOT remove the monitor isolating transformer if one is fitted.[/b]

While more modern power supplys will not function without load (like PC power supplies), most older arcade PSU's will burn out (eventually) if they are left on and without a load.

So now my question is, for J-Pac owners/users, are you disabling your power supplies?  Or are you loading them somehow? 

Why didn't ultimarc create a dummy load and include it on the board,to be compatilbe with all power supply types?

[Dave_K.]

Just adding to the question here...  I guess the larger concern is with japanese cabinets (Neo's, Astro's, Windy's...) since the monitor is powered through the PSU (100v for japanese monitors) , so you can't just disconnect it. 

I need to measure the psu outputs without a board and see if mine are modern enough to shutdown the +5 and +12 outputs when no load is present.  Still without a load, and the psu knowing this and not outputing the voltage, is there still any harm to the PSU?

[SirPeale]

I don't think they get their power from the power supply, rather that the wires may split off from the power input.  I'd recommend rewiring a bit, so you can just take the PS out, or at least putting a switch on it so you can turn it off.

[Dave_K.]

I don't think they get their power from the power supply, rather that the wires may split off from the power input.  I'd recommend rewiring a bit, so you can just take the PS out, or at least putting a switch on it so you can turn it off.

The monitor definately gets power from the PSU, and is not split off, as these monitors are 100V only, and my input is 120v.  The japanese psu will take inputs from 92V to 132V so its compateible with US line voltage, but still internally transforms to 100V for the monitor.

Rewiring the interals of the PSU to take out the isolation transformer which does the 100V output would be a real pain.

And isn't the point of a JPAC to be compatible with jamma cabs so you could just swap in a mame/pc or a PCB? 

[paigeoliver]

Easy solution, just go get some 6 volt light bulbs and put them on the +5 line. Problem solved.

[Dave_K.]

Easy solution, just go get some 6 volt light bulbs and put them on the +5 line. Problem solved.

So mod the j-pac to wire the +5 tooth to "some?" 6 volt light bulbs?

[paigeoliver]

Easy solution, just go get some 6 volt light bulbs and put them on the +5 line. Problem solved.

So mod the j-pac to wire the +5 tooth to "some?" 6 volt light bulbs?

No need to mod the j-pac, just splice a +5 wire on the harness.

[Dave_K.]

Easy solution, just go get some 6 volt light bulbs and put them on the +5 line. Problem solved.

So mod the j-pac to wire the +5 tooth to "some?" 6 volt light bulbs?

No need to mod the j-pac, just splice a +5 wire on the harness.

Sounds simple enough.  Thanks Paige!

One last question...if the regulated +5 circuit in the PSU recognizes there is no load, and shuts off +5, then is this condition still considered harmfull to the PSU?

[paigeoliver]

Easy solution, just go get some 6 volt light bulbs and put them on the +5 line. Problem solved.

So mod the j-pac to wire the +5 tooth to "some?" 6 volt light bulbs?

No need to mod the j-pac, just splice a +5 wire on the harness.

Sounds simple enough.  Thanks Paige!

One last question...if the regulated +5 circuit in the PSU recognizes there is no load, and shuts off +5, then is this condition still considered harmfull to the PSU?

I'm not really sure on that to tell you the truth.

Another option is if you have a dead game board of any kind laying around, you could wire up the +5 and a ground on that and it would provide a perfect load.

[Vicious]

This is my first time doing this so bear with me if my questions sound redundant.

Is a 6V bulb being put on each 5+ line to kill the signal?  For the few times that I've powered my cab up I've just left the JAMMA harness connected to the J-PAC as-is, but apparently from reading this thread that's not a good thing.  Should I just splice into the JAMMA harness or remove the 5+ wires from the harness and wire it that way?

[Dave_K.]

Putting a 6V bulb on the +5 line is to provide a load for the power supply (if you intent to keep it on).

The main question here is, do you need to supply a load if you intent to keep the PSU running with the J-PAC.  Second to this, is if the PSU recognizes a no load condition, and shutsdown the +5, then is that an accpetable state or does this eveually wear down the PSU as well?

[Ken Layton]

Some power supplies don't need an external load because they have internal load resistors.

The Peter Chou screw terminal power supplies are an example of a well designed power supply that can run perfectly fine with no load connected.

[Dave_K.]

Some power supplies don't need an external load because they have internal load resistors.

The Peter Chou screw terminal power supplies are an example of a well designed power supply that can run perfectly fine with no load connected.

Ken, is there a way I can tell my PSU is fine without a load? 

If there was no internal load resistors, would I still be reading +5 on the terminal with nothing attached?  Or rather, if I don't get any reading on +5 with no load attached, can I assume the PSU is taking care of it with a load resistor internally?

[kenzo42]

if you look on krick's website, where he wires up 12v for a coin door, you can see that the none of the power traces are intact on the jpac. i believe this is called a break connector.

i believe the only reason ultimarc recommends taking out the power is two fold:
1) may blow psu w/ out load
2) safety in case you install connector backwards

This is my first time doing this so bear with me if my questions sound redundant.

Is a 6V bulb being put on each 5+ line to kill the signal?

[clutch]

I apologize for the necro-posting, but did anyone ever resolve this issue?

I have a Blast City and a J-PAC on the way and I need to know if I can:

a) Leave the power connected with the J-PAC and be careful not to plug in backward
b) Disconnect the power from the JAMMA harness and hope the PSU doesn't burn up
c) Rig something so that the PSU receives a load even though not connected to JAMMA harness.

I don't want a permenant solution because I want to easily switch from mame to JAMMA pcb's.

Thanks.

[BobA]

Why not just put a switch on the arcade PS so it can be turned off when you are using the jpac.   Make sure you put an indicator light to show when it is on.   Always be careful about plugging in a PCB.  It is never good to plug them in backwards.  Make sure you jamma connector has the proper insert key to prevent a board from being plugged in backwards.

[AndyWarne]

Maybe I have over-emphasised this issue on the J-PAC pages. Ken L is correct most PSUs will not be damaged with no load. Its really only very early switch-mode supplies which have this problem, when the designers had not yet got them right. They usually would make a high-speed clicking sound before blowing.
The current J-PAC is also pretty bomb-proof against being plugged in backwards as it has zener diodes on all the inputs which end up being conencted to an incorrect voltage if this happens.

But, the monitor cant be powered from a JAMMA power supply, its just not possible for these to generate 110 or 100 volts AC!

[clutch]

Thanks for the suggestions.  I guess I'll just have to wait until I get the cab in and see what i can make out.  I've heard about equal replies to leave the power/disconnect the power.  I just don't want to fry this expensive toy I am about to receive. 

[axondump]

Hi everyone, and greetings from France! I'm new on this forum, we may have met during the Stunfest retrogaming event in Rennes, France I registered because I have some technical issues about JPAC and power supply issues. I own a New Astro City cab, and am right now in the process of making a MAMEcab using a JPAC interface!

I'm trying to up this thread (instead of creating a new one), because I have the same kind of problem. A few answers have been given already, but I'd just like to make sure I'm heading the right path!

My symptoms: clicking of PSU when using the JPAC. Everything else is fine (great pixel perfect picture, using an ArcadeVGA card and MAME). Also nothing wrong when using the cab with a standard MVS slot. Reading all of you on various forums, and asking Andy from Ultimarc directly, we narrowed the problem down to: the New Astro City's PSU doesn't like it when there is no load attached to the Jamma connector. (The Jamma power supply isn't used by the JPAC.)

So, it seems I have two solutions:
1) Adding a load between the +5V and GND to mimic the presence of a PCB
2) Trying to disconnect the AC input to the Jamma power supply (I can't switch of the whole PSU as it it used for the monitor as well)

I'd rather go with the first solution. I'm thinking of adding a (correctly sized) switchable resistance between a free +5V connector and the GND, somewhere here:


As the DC unit outputs 5V 7A, I'm thinking of a >0.8 ohm 35W resistance. I also wanna make it switchable, because I can then choose to add the load when using the JPAC, or deactivate it when using a standard PCB.


Do you think it's the right thing to do?

Thank you everyone for your useful past comments and for your help!

[axondump]

Hi again!

Sorry for the message spamming, but during the time taken for approving my 1st message on this forum, a person from the Jammaplus forum suggested I add a load to the J-PAC directly, not on the cab PSU itself. This way, I stay flexible and can continue to use other PCBs as is.

I ordered a 10 ohm resistor and a heatsink, and will set this up next weekend.

I'll keep you informed of the results