Star Tech Journal

August 1986 ( 3)
STAR*TECH Journal
Tehkan PINBALL ACTION
Intermittent Sound
By Sam Cross
Godwin Distributing
North Little Rock, AR
The somd on this kit has a habit of
getting knocked out by the flourescent
lamp flashing or fran any of various
voltage spikes which could enter the game.
Symptoms include; sound not being enabled
until the game is turned off/on several
times to the somd disappearing at random
intervals not to retum until the game is
turned off then back on again.
'Ihe tech at Tehkan advised ne to disable
the lamp so that it won't interfere on
power-up. This seeired to cure nost of the
problem but it still happened at less
frequent intervals.
'!he solution I came up with was a result
of simplicity, as I had tried several
other arrbitious tricks which didn't work
to Rrf satisfaction.
It involves resetting the somd
microprocessor each time a coin is
inserted. '!he only sacrifice is that the
"coin registered" sound is not heard, but
this is a small sacrifice.
On the board with the large edge
connector, which is the somd board with
the amplifier on it, cut the trace on the
parts side which leads to pin 13 of C4, a
74LS32, and connect a wire from this pin
13 to the Non-Banded Side of diode D2
which is right under the large edge
connector.
This modification results in the action
that \\henever a coin is inserted, the coin
switch pulls the non-banded side of diode
D2 to ground and resets the sound
microprocessor at the beginning of every
game, ensuring sound during the game.
(Provided the somd micro is working
properly.) 'Ihe solution is crude, but
cheap and easy to perform on location.
000
Monitor Horizontal Tearing: Mod II
By Victor E. Schick
Bullseye Inc.
Madison, WI
RE: S*TJ Volume 8, #5 (July, 1986) article
on "Monitor Horizontal Tear".
On Electrohone 00-7 nonitors with
horizontal tearing, I tried this
roodification and found it to be
unsatisfatory.
I have an alternate nethod, described as
follows:
I connect 1N4748 fast-switching diodes in
both positive(+) and negative(-) sync
inputs to this nonitor in the following
fashion:
JJGI,. S-IAIC ltuPt/1
_,_,
-v
lilAID
4--1
0
I Al l4'11fi
Pas.
SYNC. 1/JPLI(
+H
+V
w
6N/J
0
0
o
0
Wl'E: Both diodes mist be installed or
·you will not get vertical stability.
I have been using this nethod for 1 year
or more with no problems.
SERVICE·NAIUAL
Instructional and reference manual
entitled ELECTRONIC GAME REPAIR covering
such subjects as: Basic Electronics,
Semiconductors, Video Game Systems,
Electronic Pinball Systems,
Troubleshooting Techniques, Tools end Test
Equipment, Schematic Reeding end more.
This B-1/2 11 x 11" manual contains 85 pages
of technical information for the servicing
of electronic amusement games and is
priced at S24.95 plus S2.5O shipping.
Distributed by STAR*TECH JOURNAL.