Auto Switching MS9 / J-pac Issue

[Andypc]

I have a strange issue with my J-pac and Auto Switching MS9 when trying to switch between 15Khz and 24Khz. I have all my emulator up and running perfectly in 15Khz (Groovymame, GroovyUME etc and CRT_Emu drivers). However the only emulator I am having an issue with is the Model 2 Emu as it looks poor running interlaced and the sound is skipping. So I thought I would run VMmaker and add 24Khz modelines. Changed the jumpers on the J-pac to 15Khz and 25Khz started the PC and the 15Khz picture was all scrambled. Changed the jumper back to just 15Khz and started the PC again and the picture displayed perfectly again. Tried a 24Khz resolution and the picture is scrambled? Tried with the jumper on just 25Khz started the PC again and the 15Khz picture is scrambled again.

To cut a long story short the J-pac doesn't seem to auto switch between 15Khz and 24Khz no matter what jumper setting I try. If I start the PC in 15Khz with the 15Khz jumper selected on the J-pac and then start a 24Khz game the picture is scrambled. If I then unplug the keyboard lead to power down the J-pac change the jumper to 25Khz and plug the lead back in it syncs and the picture displays perfectly. The only way to switch between 15Khz and 24Khz is to power down the J-pac and change the jumper manually. This defeats the point of having an auto switching chassis. I thought the J-pac would auto switch with the right jumper settings.

I would just give up, but running the model 2 emu at 24Khz looks great and fixes the sound issue.

[cless]

Ive only used my J-pac for 15Khz or 31Khz input, haven't tried the med res setting, but from the J-PAC website under the monitor section (http://www.ultimarc.com/jpac2.html"), it sounds like the jumpers are filters for the different frequencies: the installed jumper of the lowest frequency dictates the cutoff. No jumpers means no filtering. Putting in the 15kHz and 31khz together happens to be a special setting where you get a somewhat garbled double screen when 31khz signals are coming in -- its still outputting at the lower 15khz setting though. I dont have my board in front of me, but if you look up the datasheet of the converter chip hes using, it probably makes sense.

So, some other things you could do:
1.) Remove all Jpac video jumpers and hope your PC doesnt output 31khz. (or leave the MS9 monitor off until you're sure its booted into 15/24khz mode)
2.) Get a tri-mode chassis and remove all Jpac jumpers
3.) Use a different video amplifier that auto-switches frequencies and lets you filter out 31khz
4.) Get an arcadeVGA card so your PC doesnt output 31khz and remove the Jpac jumpers

[Andypc]

Removing all the jumpers on the j-pac outputs composite sync and causes the screen to roll. With the jumper set to 15Khz the j-pac will only sync to 15Khz. With the jumper set to 25Khz it only syncs to 25Khz. With both the 15Khz and 25Khz jumpers set it only syncs to 24Khz. The chassis auto switches no problem.

The picture for this chassis is fantastic for low and medium resolution, so I'm not looking to change the chassis and the HD4850 with the CRT_Emu driver is actual much better than the ArcadeVGA I am using in my other cab. It runs all the games in GroovyMame at the right resolution and refresh rate. The Arcade often runs games at the wrong refresh rate.

I could try a different video amp, but just always assumed the j-pac could cope with resolution changes.

[cless]

woops, misread that. Yeah, removing the jumpers won't work either in that case....

[cools]

The JammASD may work differently. If I had time to test I'd do so, but I can't even get within 6m of the cab at the moment.

[brad808]

Removing all the jumpers on the j-pac outputs composite sync and causes the screen to roll.

Sorry to bump this thread up but I'm facing the exact same issue. I'm looking to bypass the sync on the jpac while keeping the video amp portion all in tact. My plan is to just break trace at the vga input and connect direct to the jamma pins. If not composite sync should I just be hooking up v-sync?

[brad808]

Never mind problem solved. Simply remove all jumpers and add a small blob of solder connecting vsync and hsync at vga connector input.