STAR* TECH Journal
January 7 992
Data East Star Trek
Ramp Up
Mechanism
Troubleshooting
Double Dragon Rom
Enables
Arnie Aarnstad
Data East Pinball
Melrose Park, Illinois
James Beck
Greater Southern Distributing
Atlanta, Georgia
SYMPTOM
SYMPTOM
The Up Down Ramp does not always come back
down.
A Double Dragon board that powers up ok, but
there are brownish blocks around the two main
charactors. It looks like a object Rom problem,
but then again ...
SOLUTION
Check the Ramp Up switch to insure that it is
closed when the ramp is up. If the switch is func-
tioning properly, check to make sure the coil bobbin
screw on the latching mechanism is secured. A
limited number of games did not have loctite ap-
plied and we suggest at your next maintenance
service call you tighten .and loctite the bobbin
screw. See Figure 1.
NOTE
First off, I've yet to have just one Rom go bad on
the Double Dragon boards. Usually a power
supply failure smokes a bunch of 'em, but it's
bound to happen eventually. The characters do
have different parts/ colors mapped into several
ROMs, so if one went bad it could cause the
symptom.
SOLUTION
But, the most common cause, is the fact that the
board is literally covered with 74LS153's/
74LS157's that have an active low enable on pin
15 and Vee on pin 16. The enables are pulled
directly low to ground and any little thing, like a
quarter falling on the board, due to its' great
location right under the cash box, stands a good
chance of popping one of the enables, sometimes
a whole row.
PROCEDURE
(G\X,,
Tighten This
~--.,__-
Screw
0
If you look along the edge of both boards, right
next to the ribbon cables, you'll see the little
guys. Use a probe to look for floating pin 15's.
When you find one, you've got your culprit.