need help with Sega Jamma IO A board

OldFoo · Post by **OldFoo** » Tue Mar 15, 2011 10:44 pm

Hi,

I am new here, been reading these forums for ages tho. Last week I bought a naomi system with a Sega Jamma I/O board, which turns out is the A type board that requires a coin counter to run.

I am trying to diagnose why there is no power to any of the unit, psu, anything. I have a couple of questions:

1. The stock psu is wired like this by me today:

Should the psu power up without anything besides power being supplied? E.G. no naomi board plugged in? I've tried this and nothing.

2. Is there some pins I can short to enable the psu to "on" position? kinda like shorting out two pins on an atx psu to make it stay on when power plug is plugged in?

3. There is a jumper seen here:

What is this for? I assumed it was to assign where 5 volts comes from, e.g. psu or jamma harness, if so which setting is what?

4. I did a search for wiring the coin counter/coin stuff in the jamma io baord, but andy's response was a few links which are no longer available. Does anyone have working links on how to either solder to sega jamma IO A board to disable coincounter or how to wire one up??

Also thanks for this awesome naomi site, and you dudes rock. [/img]

OldFoo · Post by **OldFoo** » Tue Mar 15, 2011 11:03 pm

PSU should power up, even when nothing is connected. Can you provide a more detailes photo of how you are connecting the PSU to mains?

Oh, welcome to Sega-Naomi.com!

OldFoo · Post by **OldFoo** » Tue Mar 15, 2011 11:56 pm

thanks cageman!

So I jury-rigged power in the square Black and White wire connector that comes out of the psu. I was told from the neo-geo.com forums that this was the ac input of the unit. Also the diagram on the psu indactes this is the ACN and ACL. I'm assuming since we're dealing with AC polarity doesnt really matter, but maybe it will when i plug it into my cab?? I forget what my father used to call it, when the ACN and ACL were reversed, causing _____.

I will post up a picture if you like, but I checked for continuity from the wall plug to the psu by opening up the power supply and tracing the cables to the psu board. There is continuity.

OldFoo · Post by **OldFoo** » Wed Mar 16, 2011 12:11 am

The PSU could have a blown fuse. You would have to open it to find out.

OldFoo · Post by **OldFoo** » Wed Mar 16, 2011 12:13 am

ok also the psu isn't a sun brand, it says JQA on the lid.

I opened the case up to check for a fuse or to peek around for some leaking/blown components like caps and broken overheated diodes etc, everything looks fine, just really dusty. The LED does not light up, there is 120 volts coming into the circuitboard, question is where is it getting fumbled?

Fuse has continuity, so fuse isn't blown...

Here's some pictures:

Only fuse i could find, which tested fine:

Sega Jamma I/O board, is the A signify it is an A Revision?:

OldFoo · Post by **OldFoo** » Wed Mar 16, 2011 8:45 am

Most probably a fault in the high voltage circuit (you could check the rectifier diode(s) as a start).

OldFoo · Post by **OldFoo** » Thu Mar 17, 2011 7:56 am

all sorted out now, power supply was shot. built a new one out of an old dell pc atx psu for the time being until a sun psu comes into my hands