Troubleshooting a Nanao ms9 with JPAC

[Deathgaze]

Hey all. I've connected my cabinet to the JPAC but when doing that the monitor just shows a black screen with messy green lines and random green specs (think static on a TV but green)
But I've found something odd. When I unplug the jpac from the Usb port, it shows the image but it's yellow tinged and the image is rolling vertically.

I'm quite new to all this so sorry if it's an easy fix.

I've uploaded a video.


When you can begin to see somewhat of a clear picture it's when I unplugged the JPAC USB

[buttersoft]

Looks like a sync issue. Without the USB, how is the Jpac getting power?

What happens when you adjust the V-hold pot on the chassis?

[Deathgaze]

Looks like a sync issue. Without the USB, how is the Jpac getting power?

What happens when you adjust the V-hold pot on the chassis?

I can't tell you the results right now for the V Hold pot as I'm at work (i'll tell you when I get home what happens), however the JPAC wasn't getting any power what so ever when unplugged. It was just metal for the JAMMA -> VGA to travel through.

[Zebidee]

I think I know what your problem is.

When powered, the JPAC amplifies the RGB signals and converts H+V sync into composite sync.

On your JPAC there should be a set of jumpers with "15khz", "25khz" and "31khz" written next to them. This corresponds to what sync signals the JPAC will allow through to your monitor (the idea is that unless the jumper is on, that frequency "range" will be blocked, thus protecting your monitor from frequencies that might damage it). If there is no jumper then no signal.

Generally you would want a jumper on 15khz in order to let CGA through to your monitor.

If the 15khz jumper is off then you won't get sync (what we saw in the video). When you pull out the USB (power) the JPAC sync combining circuits are not active and passively lets through your sync (& RGB), but obviously it is not combining properly into composite sync as the JPAC has no power (which is why we see a rolling, somewhat weird picture).

Hope that explains everything. I'll try to post a picture later.

Zeb.

[Deathgaze]

I think I know what your problem is.

When powered, the JPAC amplifies the RGB signals and converts H+V sync into composite sync.

On your JPAC there should be a set of jumpers with "15khz", "25khz" and "31khz" written next to them. This corresponds to what sync signals the JPAC will allow through to your monitor (the idea is that unless the jumper is on, that frequency "range" will be blocked, thus protecting your monitor from frequencies that might damage it). If there is no jumper then no signal.

Generally you would want a jumper on 15khz in order to let CGA through to your monitor.

If the 15khz jumper is off then you won't get sync (what we saw in the video). When you pull out the USB (power) the JPAC sync combining circuits are not active and passively lets through your sync (& RGB), but obviously it is not combining properly into composite sync as the JPAC has no power (which is why we see a rolling, somewhat weird picture).

Hope that explains everything. I'll try to post a picture later.

Zeb.

With my limited knowledge of all this I did try playing around with the jumpers. The nanao MS9 is dual sync 15/24khz so I got those jumpers on. Once I discovered the affect of removing the USB power I than tried plugging the USB back in and removing both jumpers but I still get the black screen with green jumbled mess.

[Zebidee]

Try different combinations of jumpers especially just 15khz, or 15khz+31khz

[Deathgaze]

Zebidee
I tried every possible combination of jumpers but to no success.

Buttersoft
Mine doesn't have a v hold pot, just a v size and posi.

However with those responses I realised that my "sync OK" LED on the jpac is off. If anyone has any recommendations I'm all ears. :p

[Zebidee]

Pretty sure there's a V hold pot there somewhere, maybe it is that position pot I'm thinking of. I used to own a Nanao 29" in a "Candy" cab (Astro City).

Are you absolutely sure that you are outputting 15khz?

Have you tried bypassing the JPAC, feeding the sync directly into the monitor? The Nanaos are pretty forgiving, worst you'd get is a not-so-bright picture.  You can just twist the sync lines together for composite so long as your sync output is positive/positive or negative/negative (I can feel Buttersoft wincing as I say this, ).

Maybe you aren't outputting vertical sync? Or maybe something do do with your VGA cable. I'd be testing everything, get the multimeter out and test those sync signals. Might not be the JPAC.

[Deathgaze]

Yeah my Nanao MS9 is in my New Astro City. I guess I'll give all this a crack on the weekend. I'll keep you up to date. Thank you for being patient with me thus far.