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Blast City Jamma problems

jessejames13

jessejames13

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So, I have had my Sega Blast City cab for years now. For the past year I’ve been running a Sega Naomi 2 connected to a campcom i/o and a second psu. It was connected through VGA. Everything ran great.

I just got a CPS3 system today actually. Third Strike is my favorite fighter, so it’s getting swapped in. It’s running 5 volts on the jamma edge (after adjustment). I get perfect sound, and can even fight blindly. But I’m getting no picture at all from the jamma. The monitor powers on and makes the “right” clicky sound.

Inside is a Phillips auto tri sync monitor according to the sticker on the tube. The chassis frame says nieman video displays.

Any help would be greatly appreciated.
 
Is it manual sync or auto? If it's a manual sync, you need to change the dipswitches to accept 15khz.
 
Is there a switch on the monitor remote board for changing the circuit impedance?


Some Tri-sync monitors require it.
 
First of all, try the CPS3 on another display if at all possible and see if you get video (e.g. via cheap supergun).

Never had any issues with CPS3 on my Blasts, nor have I heard of anyone else having such a problem. If other boards are working properly on the Blast in 15khz, it could be a problem with the CPS3 mobo.
 
The only switch on the break out board is:

Left- 75ohm1v
Right- 1Kohm3v

the rest are brightness vhold etc.

Let’s see. for cabs to test on I have UMK3, MVS 6 slot and a Vewlix C. The vewlix is VGA only in it’s current setup. Think i could test on the UMk3? It’s at work.
 
Didn't notice you said you normally use VGA, can you run the Naomi through Capcom IO and do video via JAMMA OK?
 
Just ran to work and attached the CPS3 to the UMK3, picture and audio were perfect. I’ll head back home and try the capcom io through jamma. My suspicion is that I’m missing something on the blast itself.
 
I’m getting no picture through the capcom IO’s jamma. Through the VGA on the Naomi, it’s working fine still.
 
Try putting the Naomi in 15khz mode. See if you have a picture then.
 
jessejames13 said:
I’m getting no picture through the capcom IO’s jamma. Through the VGA on the Naomi, it’s working fine still.
Click to expand...
take a picture of your remote board on the blast and send it to us. Does it have dip switches?
 
rewrite said:
Try putting the Naomi in 15khz mode. See if you have a picture then.
Click to expand...
I tried 15hz through VGA, which showed up fine. Then I tried 15hz through jamma and again, no picture.



kuze said:
take a picture of your remote board on the blast and send it to us. Does it have dip switches?
Click to expand...
Only the switch I posted above.
 

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That looks like a rodotron or wei ya chassis :(

Don't know much about those other than they're not the best of quality
 
Since I don't think it's actually been asked. Did you flip that switch and try again with JAMMA?

Can't hurt. Probably wouldn't flip it while it's on though.
 
Yeah, I think that a rodotron 666 you need to switch the impedance switch for the 15khz or it won't display.

Those are dodgy chassis's that don't actually like changing between resolutions that much.

Mine recently died for no reason. Literally the fist time I put my Naomi in it.

Here's useful link if it is a Rodotron

https://wiki.arcadeotaku.com/w/Rodotron_666
 
rewrite said:
Since I don't think it's actually been asked. Did you flip that switch and try again with JAMMA?

Can't hurt. Probably wouldn't flip it while it's on though.
Click to expand...
Yup. In both positions, and with both with the naomi having dip 1 in the up position and with the cps3.

Blackfish said:
Those are dodgy chassis's that don't actually like changing between resolutions that much.
Click to expand...
Weird. I literally had it switching resolutions multiple times a day when i had the crt emudriver setup. Of course, that was through VGA. Thank you for the link. I plan on doing some small geometry fixes when i figure this out. When i flip the switch it feels like nothing at all is happening. Is there any indication when it changes, like a sound or hum, screen wiggle?

Something worth mentioning:

The lines for the kick harness has been cut at the blast i/o board. It is ONLY the kick harness that has been cut. The kick buttons are connected through a separate kick harness directly to whatever board is used. Could the lack of a kick harness connection interfere with the video signal from the jamma? Everything else works fine (buttons all register etc.)
 
Last edited:
Just a thought... You said that the 15khz signal was fine through the DB15HD connector but not through JAMMA - but how is the video signal connected to the monitor for JAMMA boards?

My Cyber Lead has the same setup and a JAMMA IO board for exactly this, I assume the Blast has the same somewhere, is there a switch that needs to be used to switch between input from DB15HD and direct RGBs or is there a board the DB15HD needs to be plugged into to get video from JAMMA boards?
 
xodaraP said:
Just a thought... You said that the 15khz signal was fine through the DB15HD connector but not through JAMMA - but how is the video signal connected to the monitor for JAMMA boards?

My Cyber Lead has the same setup and a JAMMA IO board for exactly this, I assume the Blast has the same somewhere, is there a switch that needs to be used to switch between input from DB15HD and direct RGBs or is there a board the DB15HD needs to be plugged into to get video from JAMMA boards?
Click to expand...
Jamma leads into the Blast City I/O board. There is no DB15HD connection that comes from the I/O. That would actually solve the problem right there. It feeds up to the monitor with a direct connection through the chassis from my understanding. A second connection is the DB15HD line that just comes right from the chassis. If there were a switch somewhere that I’m just not aware of, that would be cool, cause I’d be playing Third Strike after I found it. haha
 
I have a feeling that the Jamma video signal is disconnected. My chassis only ever worked through the VGA cable. I never actually tried 15khz, only 24 and 31khz then it died.
 
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