Star Tech Journal

Nintendo Dual Cabinet Interference Cure
James Beck
Greater Southern Distributing
Atlanta, Georgia
A common complaint heard from dual-cabinet
converters ...
PROBLEM
I am trying to convert a Nintendo dual cabi-
net (sit down) to two JAMMA wired games,
one is Eswat, the other UN Squadron. The
problem is interference between, I think, the
two monitors.
I have used shielding between the monitors
(metal), separate power supplies, and sepa-
rate isolation transformers. I have also tried
getting a little more distance between the
monitors.
ing onto these signals, but the difference
causes a magnetic "beating" of frequencies
in the fields.
This beating is the ripple you see. The verti-
cal sync is most noticeable because it is at a
low enough frequency our eyes can perceive
it. In the original game this was no problem
because the two sides of the board set used
the same master oscillator. The only solu-
If I pull one monitor out about 6 more inches,
the problem stops ...
The yokes are about 5 inches apart. If I pull
one monitor out about 6 more inches the
problem stops, this is great but it makes it
very difficult to close the cabinet! Any help
would be greatly appreciated.
SOLUTION
The problem you're experiencing was cov-
ered here and in STAR*TECH Joumalin the
past year (by me), but I'll recover the quick
version here.
The problem is caused by the magnetic flux
of the yokes being so close together. The sync
signals that produced by two different
boards (even of the same type) are a little dif-
ferent. The monitors have no problem lock-
tion I can give you is to ust as much shield-
ing as possible between the two yokes.
In the cocktail games you must make sheet
metal cones to fit over the yoke assemblies
and silicon them in place. In the uprights
you can get away with a sheet between the
monitors.
Make sure you ground the shields to earth
ground and the chassis.
NOTE
Eswat is a System 16 Sega pinout PCB but
in the Sega USA kit they have included a
Sega to JAMMA interface board and a
JAMMA harness.