12V Stereo Amp in Jamma Adapter

[dmauro]

I am having a problem with the wiring of my stereo amp I'm using for my console to jamma adapter. It says it requires 12VDC, so I got a proper size N type coaxial dc power connector, and wired it to my Jamma fingerboard so that the center of the barrel is going to the +12V pin on the fingerboard, and the outside of the barrel is connected to the ground on the fingerboard. The amp does not power up.

I tested the amp with a 12VAC power adapter plugged into the wall and the amp powers up.

What am I missing here? Should this actually be using AC instead of DC, and if so, what kind of power connector do I need? Am I just wiring this wrong?

[antron]

I tested the amp with a 12VAC power adapter plugged into the wall and the amp powers up.

powers up, but will it amplify a signal?

many jamma power supplies require a full load to get going (lika a game). this is why ultimarc does not do this with the jpac.

[dmauro]

I tested the amp with a 12VAC power adapter plugged into the wall and the amp powers up.

powers up, but will it amplify a signal?

many jamma power supplies require a full load to get going (lika a game). this is why ultimarc does not do this with the jpac.

I didn't test if it amplifies, but the light indicating power is on.

How do I fully load the Jamma connector?

[yosai]

Plug in a PCB. Probably best to use your cheapest.

[dmauro]

Isn't there something I can wire up to the fingerboard to draw the necessary power to get things going?

[antron]

Isn't there something I can wire up to the fingerboard to draw the necessary power to get things going?

a high wattage resistor. if you don't know exactly what you are doing you will destroy your stuff.

[dmauro]

Where can I find out exactly what I need to be doing? Once I had a resistor at the correct wattage for the +12V line, I would connect it between the 12V and ground lines? And the same for the +5V line if I wanted to draw power from that one?

[antron]

you should just go get a 12V DC power supply from Radio Shack and forget it. or look through all the junk in your house, you probably have one.

[dmauro]

I also need to run 5V for the ultimarc video amp.

[antron]

my power supply puts out 5V even without a full load, maybe yours does too.

also most consoles supply this as well, either on the video cable or the controllers you hack.

[dmauro]

I'm using an ultimarc PS2 VGA adapter and a separate video amp from ultimarc as well. He says the VGA cable puts out the 5V needed for the video amp, but it's definitely too dim, so I don't think the video cable is putting out the 5V he thinks it is. And I think PSX controllers put out something weird like 3.3V.

[antron]

I'm using an ultimarc PS2 VGA adapter and a separate video amp from ultimarc as well. He says the VGA cable puts out the 5V needed for the video amp, but it's definitely too dim, so I don't think the video cable is putting out the 5V he thinks it is. And I think PSX controllers put out something weird like 3.3V.

you need a multi-meter (specifically the DC voltage function)

there is a thread here reporting that the ultimarc PS2 video adapter has a problem with the red line when used with some monitors. mine had this problem. i ordered the amp hoping it would fix it, but then all my stuff was lost in a move before i tested it. if this is your problem, maybe return every thing to ultimarc for a full return (i did with my 2 faulty controller adapters). his entire line of ps2 stuff is crap.

[dmauro]

I could save myself about $20 and keep my console adapters much tidier if I can figure out how to do this without a DC converter. How do I find out how many watts I need to draw to get it to work? Is the wattage standard for Astro City power supplies??

[antron]

reading around on the net I see a supergun should supply 0.5 to 1 amp on the 12V line. you should try for a quarter amp to keep the heat down. it should get the amp going, but I may be wrong. you may need to draw on the 5V line too.

from P=I*V that gives 12*.25=3 Watts. Use something a bit higher, like 5 Watts.

from R=V/I we get 12/0.25=48 Ohms. Ar about 50 Ohms

So you need a 5 Watt 50 Ohm power resistor.

It is possible to build a 50 Ohm resistor with larger ones by putting them in parallel, or with smaller ones by putting them in series.

you may need a multi-meter, so you can adjust the power supply.

[dmauro]

Awesome. Thanks for the tips, that should help get me started. I didn't think to look at supergun docs, but that was a good idea.

[dmauro]

As it turns out, the problem was simply that the connection for the plug on this amp is kind of crappy so I just had to wiggle it around until it connected. This is now working just fine. What I learned from this:
1) an Astro City PSU always provides voltage on the +5, -5 and +12 lines with no need for load.
2) always test everything with a multi-meter before making assumptions (just because the amp wasn't powering up, didn't mean +12v wasn't being supplied).

Thanks for the help though. This thread was still very informative for me.

[jonny5]

his entire line of ps2 stuff is crap.

not true....this is an opinion....it works fine.....many people have no complaints and with the newest version chips in the control adapters there arent any issues either.....

if could just as easily be said that the issues lie in your hardware, not the ultimarc stuff, as lots of people dont have the issues you did

i still stand by andy and his products......

[dmauro]

Yeah, I've got to say, despite the fact that I'm a little upset his PS2 VGA adapter doesn't do 480p as he sort of suggested it would, he's been great about keeping in contact via email, and the adapter works great other than that, as does the video amp I purchased from him.