Sega Blast City - PSU voltage drop and non-functioning games

Yamazaki

Belnar Institute Student
15 Year Member
Joined
May 12, 2006
Posts
1,234
I got my Blast City since last July and it actually plays most of my games perfectly.


buuuuut

I got issues at the moment with a korean Gunforce II pcb and the PSU.


screen attached shows what I get when I hook up the game to my cab.

--> the game works perfect on my MAK on TV though!




what I also noticed is that I got a drop of about 0,8v from Jamma connector to the game pcbs...


i.e. Light Bringer has 5,5 on the Jamma loom but 4,7 on the pcb side...





any ideas what might be the issue here?

I was told horizontal frequency but changing the wide/narrow pot on the backside did not help....




Gunforce II on my cab...
33664723_10216568603507103_6311782662872760320_n.jpg
 

Kid Panda

The Chinese Kid
Joined
Jun 13, 2010
Posts
12,514
Well first off, that's not a legit gunforce II, also your psu prolly needs a recap.
 

Yamazaki

Belnar Institute Student
15 Year Member
Joined
May 12, 2006
Posts
1,234
it's a korean pcb as far as I know.


or you mean it's a boot?
 

ChuChu Flamingo

We have purposely, trained him wrong, ...as a joke
10 Year Member
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Nov 23, 2010
Posts
2,763
You should really have 5.0V at the jamma edge connector. 4.7V at the jamma edge connector of the arcade board means most chips won't be working right, especially those furthest away on the board.

also correct me if im wrong, but I think the wide/narrow adjustment has nothing to do with frequency. I believe it just sets the maximum and minimum size you can do.
 
Last edited:

NEgO MANIAC

Sieger's Squire
15 Year Member
Joined
Jan 5, 2004
Posts
804
Not sure if your PCB needs -5v, but the Blast does provide -5v. You will need a Negatron between the JAMMA connector and PCB edge connector.
 

radiantsvgun

They call him Mr. Windy
15 Year Member
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Sep 29, 2007
Posts
1,687
That's a legit Korean version- Some of those older boards are wonky on tri-sync monitors. I'd go with trying to recap the psu, it will help in the long run.
 
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