Star Tech Journal
Issue: 1989-June - Vol 11 Issue 4 - Page 5
SegaHang On
Input Caps
Capconi Bowling
Audio Overheating
Jim Allen
Eylers Vending Inc.
Frederick, Maryland
James Beck
Greater Southern Distributing
Atlanta, Georgia
SYMPTOM
PROBLEM
I've noticed this problem with some of the
Capcom Bowling circuit boards: The audio
amplifier chip overheats and the volume
control is very noisy.
The accelerator is stuck at 80 mph continu-
ously. The pot and harness has been elimi-
nated as probable causes and troubleshoot-
ing the cabinet wiring yields no results.
PROBLEM
SOLUTION
I traced the problem to C9 in the audio
section. It seems that on some boards the
voltage across C9 is opposite to the polarity
of the capacitor (4.7 mf, 50v). This allow
current to leak into the volume control
~which causes a DC offset on the output of the
audio chip which puts DC into the speaker.
This can easily be observed by powering up
the board and then hooking up a speaker to
the speaker leads. The speaker cone will
either push out or suck in depending on the
polarity of the DC on the leads. This DC in
the speaker will cause distorted sound due
to the cone bottoming out and eventually the
voice coil will heat up and come unglued.
SOLUTION
This can be remedied by replacing C9 and
installing it in the proper polarity or by
replacing C9 with a non-polarized cap of the
same value or by replacing C9 with 2 caps
000
Right next to the 50 pin control harness
connector is a row of small electrolytic ca-
pacitors. Those are the input filters for the
analog controls. There are probably going to
be some unused ones, but if you attach your
multimeter from ground to the positive side
of one of these caps the voltage should vary
when one of the control pots is turned. If all
of the inputs look OK there is a CD4053, a
CMOS analog multiplexer, and an ADC0804
analog to digital converter. Replace both of
them as a unit.
NOTE
One thing to keep in mind is that the analog
control input section gets its ground
through a really wimpy board trace, and if +5
was shorted to the control ground, the trace
could get blown open at a weak point.
MONITORS! MONITORS! MONITORS!
Your video game depends on this component more than
any other, yet it can be the most frustrating part to service.
Now, STAR*TECH Journal has published a manual of over
120 pages listing problems, symptoms & solutions to nearly
every monitor used in the video game industry for the last
10 years! 1979 to 1989. It's the BEST OF STAR*TECH
JOURNAL: MONITORS. Priced at $49.95 ($3.50 s/h). This
manual should be on every service bench! Available pre-
paid or C.O.D. from STAR*TECH Journal, PO Box 1065,
Merchantville, NJ 08109. Phone: 609/662-1080. Fax: 609/
488-9326. Guaranteed satisfaction or your bucks back.
Input Caps
Capconi Bowling
Audio Overheating
Jim Allen
Eylers Vending Inc.
Frederick, Maryland
James Beck
Greater Southern Distributing
Atlanta, Georgia
SYMPTOM
PROBLEM
I've noticed this problem with some of the
Capcom Bowling circuit boards: The audio
amplifier chip overheats and the volume
control is very noisy.
The accelerator is stuck at 80 mph continu-
ously. The pot and harness has been elimi-
nated as probable causes and troubleshoot-
ing the cabinet wiring yields no results.
PROBLEM
SOLUTION
I traced the problem to C9 in the audio
section. It seems that on some boards the
voltage across C9 is opposite to the polarity
of the capacitor (4.7 mf, 50v). This allow
current to leak into the volume control
~which causes a DC offset on the output of the
audio chip which puts DC into the speaker.
This can easily be observed by powering up
the board and then hooking up a speaker to
the speaker leads. The speaker cone will
either push out or suck in depending on the
polarity of the DC on the leads. This DC in
the speaker will cause distorted sound due
to the cone bottoming out and eventually the
voice coil will heat up and come unglued.
SOLUTION
This can be remedied by replacing C9 and
installing it in the proper polarity or by
replacing C9 with a non-polarized cap of the
same value or by replacing C9 with 2 caps
000
Right next to the 50 pin control harness
connector is a row of small electrolytic ca-
pacitors. Those are the input filters for the
analog controls. There are probably going to
be some unused ones, but if you attach your
multimeter from ground to the positive side
of one of these caps the voltage should vary
when one of the control pots is turned. If all
of the inputs look OK there is a CD4053, a
CMOS analog multiplexer, and an ADC0804
analog to digital converter. Replace both of
them as a unit.
NOTE
One thing to keep in mind is that the analog
control input section gets its ground
through a really wimpy board trace, and if +5
was shorted to the control ground, the trace
could get blown open at a weak point.
MONITORS! MONITORS! MONITORS!
Your video game depends on this component more than
any other, yet it can be the most frustrating part to service.
Now, STAR*TECH Journal has published a manual of over
120 pages listing problems, symptoms & solutions to nearly
every monitor used in the video game industry for the last
10 years! 1979 to 1989. It's the BEST OF STAR*TECH
JOURNAL: MONITORS. Priced at $49.95 ($3.50 s/h). This
manual should be on every service bench! Available pre-
paid or C.O.D. from STAR*TECH Journal, PO Box 1065,
Merchantville, NJ 08109. Phone: 609/662-1080. Fax: 609/
488-9326. Guaranteed satisfaction or your bucks back.
Future scanning projects are planned by the International Arcade Museum Library (IAML).