JAMMA cab conversion. So many power worries. Help!

[MaximumFish]

Hey all,

I recently acquired an old JAMMA cabinet that I plan to convert for MAME, while keeping as much of the original cab as possible. This means the monitor, controls and coin mech. I've already built the PC for it and have invested in an ArcadeVGA and J-PAC, as they seemed by far the easiest and most foolproof way of doing what I want. But then, while reading around various sites I started to get concerned about the amount of people out there warning about the dangers of not running an isolated power supply for the monitor, as well as checking various grounding points, possibly removing the low power output that would've powered the game board, and finally making sure the coin mech works off 5v and not 12v.

Plenty of places warning about these things, but none of them offering advice about how to check such things! Thus, I come to you, o' forum members, for said advice.

First off, here's the main places I refer to when talking about the above warnings:

J-PAC Installation instructions

It is usually preferable to remove any low-voltage game board power supply which is fitted inside a JAMMA cabinet, leaving only the monitor powered from AC mains.
...
Most older arcade monitors require an isolating transformer. DO NOT REMOVE THIS if fitted otherwise the cabinet and monitor frame will be directly connected to the mains power supply!
...
Double check the monitor frame and the control panel are directly connected to ground.
...
Ensure that if the cabinet has an electronic coin door, this sends a 5 volt signal, not a 12 volt, otherwise the J-PAC will be damaged.

This site's very own monitor FAQ

From a question by Unyon, "Someone mentioned in an earlier thread that you can damage your PS if it is on and the game is not connected. I hadn't seen or heard this anywhere before, and before I go and kill my PS as I convert my cab, would someone kindly confirm or dispell this? Thanks."  To which Powerjaw responded, "It's true. Just do a search with Dejanews for "power supply load" and you'll find lots of talk about how you need a proper load on the power supply or it will burn out."

There are others but these are the main ones, certainly.

So, I've taken a few pictures of the insides of my cab in the hope that you guys can help me identify the parts along with what I need to disconnect, what I need to leave, and what I need to prod with a multimeter! First off we have what I believe is the power supply:



And closer shots of each of those parts:



At a guess I'd say one of those is the isolating transformer and one is maybe the low voltage supply?

Finally, here's the monitor board:



I apologise that they're not the best shots. The CRT tube is in the way, and I don't want to risk removing it without help just yet.

Anyway, I'm desperately hoping someone will recognise this lot and can direct me insofar as what I need to do to make this thing safe before I try rigging up a PC and turning it on!

Much thanks for any help you give me!

Max

[grbgemen]

i too am in the same situation.  i was kind of waiting until the last minute to figure it all out but i just realized that its getting closer and closer for me to start hooking up the internals. 

my cabinet was a converted stargate.  It is jamma wired with an isolation transformer and similar power supply. 

[G1zm0]

hi the top picture shows the monitor psu,(isolation transformer) that is required to run ac to the monitor(, the other box is the jamma psu, that  converts the ac to dc to gives the power to the pcb game jamma board (5 & 12v dc) and power to the coin mech, if the jpac is getting powerd of the pc psu then the jamma psu is made redundant, power the coin mech from the 5 volt line in the floppy power lead, the pc will power the rest, im at this stage to

[grbgemen]

so basically unhook all the wires from the jamma power supply and leave the isolation transformer alone.  so i can just remove the entire jamma power supply as its no longer needed correct?

and power the coin mech using the pc power supply.  5 volts of course. 

[MaximumFish]

hi the top picture shows the monitor psu,(isolation transformer) that is required to run ac to the monitor(, the other box is the jamma psu, that  converts the ac to dc to gives the power to the pcb game jamma board (5 & 12v dc) and power to the coin mech, if the jpac is getting powerd of the pc psu then the jamma psu is made redundant, power the coin mech from the 5 volt line in the floppy power lead, the pc will power the rest, im at this stage to

So just to be sure... the smaller block is the monitor PSU and the long, thin one is the pcb supply? Thanks.

I still need to check those earth points though, right? Especially if I remove the pcb supply?

[MaximumFish]

Sorry to bump a really old thread, but I've just got to the point where I can start looking at this in detail again so I'm really hoping someone can help me iron out the few points not already addressed.

In a nutshell:

1) If I remove the JAMMA psu, do I need to do anything to the isolation transformer to stop it burning out?

2a) How do I check that I haven't somehow connected the cabinet and/or monitor frame directly to the mains? (Or is that not a concern if I leave the isolation transformer in there?)

2b) How do I check that the monitor frame and control panel are connected to ground?

I'd really love to get this going soon. I have all the parts ready and waiting, I just need to make sure I'm not going to blow myself up!

Thanks again,

Max

[grantspain]

to remove the jamma psu simply disconnect the mains input wires and safely isolate them
leave the transformer in place and all it wiring except the wires that go to the jamma power supply

thats does not look like an iso transformer,it looks like a standard stepdown and judging from the way this wired i would say that the cab is in the u.k

[MaximumFish]

Wow, you're good! Yes it is in the UK.

Sooo, if I have no iso transformer and I disconnect the Jamma PSU and rig up my PC using the J-PAC, will that be safe? Or is there an iso transformer on the main monitor board perhaps?

Thanks once again for your help!

[grantspain]

you need to keep that stepdown transformer in the cab,all you need to do disconnect the mains to the jamma power supply
that mtc9000 has all the correct hardware already installed for it to run safe
also do not be concerned about earths as i can see that cab looks to be earthed just fine

so to sum up all you need to do is disconnect the purple and green wires on the jamma psu and isolate them(either by cutting the terminals off and use connector block-remember each wire must not touch the other so make sure they are individually isolated)

[MaximumFish]

Brilliant! Thanks again for what I hope is the final time.

I'm getting ready to plug it all in as I type...

[Arch]

Please report back here on how it all went when you plugged it. I have bookmarked this thread, because I am doing the same thing to my Jamma cabinet when I pick it up from my parents' place in mid may. Can't wait.

[MaximumFish]

Ah, well you're in luck!

I disconnected and isolated the two wires that grantspain mentioned, connected everything up and turned it on. The degaussing hiss was quite alarming but it's been so long since I used a CRT that I forgot that it's entirely normal. After that it all worked and the cabinet didn't electrocute me.

I do need to replace a couple of capacitors as the picture is too big to fit on the screen and it wobbles a bit, but the main thing is that it does work and it's safe!

I can certainly recommend the J-PAC and ArcadeVGA for what it's worth. They made everything a whole lot easier.

[porkins]

You will need to mess with the vertical size, position, and hold, and also possibly the horizontals. But you should be able to do so and make the picture fit and fix the wobbliness.