Star Tech Journal
Issue: 1994-April - Vol 16 Issue 2 - Page 17
April 1994
So IF TIIE PICTURE TUBE GOES, IT JUST DOESN'T DO ITS
JOB, AND IT USUALLY DOESN'T TEAR TIIE BOARD DOWN
WITII IT?
Exactly.
IN TIIE CASE OF A SUSPECTED BAD FLYBACK, CAN YOU
1'._""rAR TECH JoURNAL
capacitor- the two right end legs are connected to-
gether and the two left end legs are connected to-
gether, with the capacitor in the middle. It acts as a
fuse and a safety cap. If the voltage goes too high
or the current goes too high, that cap blows. Note:
Some models DON'T use the 4 lead caps.
DISCONNECT THE HORIZONTAL OUTPUT'S COLLECTOR
LEAD AND POWER UP TIIE CHASSIS TO SEE IF TIIE OTIIER
COMPONENTS ARE ALL GOOD?
No, because too many of the
voltages are coming through
there that are needed for the
chassis to come up. Every-
thing but the AC derived
power would be dead if you
did that.
So
WHAT DO WE MEASURE TIIERE?
Infinity. If you measure any
resistance, it's shot. Replace it.
WHAT OHM READING DO WE
WANT ACROSS PINS
1 AND 4 OF
fflE VOLTAGE REGULATOR?
150 to 220 ohms you might ex-
pect, but it varies by meter
model.
HOW DO YOU MEASURE A
BAD FLYBACK? CAN YOU ISO·
AND WHAT'S ACCEPTABLE MEA·
LATE IT?
SUREMENT OF Qll?
You can measure if the pri-
mary windings are shorted
together normally you'll mea-
sure a handful of ohms,
maybe 2 or 3. If you're into
zero or 1 ohm, you've got a
problem ... But on the 7000's
they're notorious for blowing
the safety capacitors.
With no power and in the di-
ode test mode, you should see
similar measurements of in-
creasing ohms -just as if you
were reading across an 1N4004
diode.
So,
WE SHOULD READ ONE OF
fflOSE TO GET A BETTER IDEA OF HOW OUR METER READS
DIODES IN fflE DIODE MODE AND RESISTANCE MODE.
Is TIIAT C36?
Yes, and C39. And all that stuff on the schematic
under the flyback-you've got a handful of diodes
and a couple of caps-any of that stuff will blow your
fuse.
Also, D18 needs to be replaced if you blew a sec-
ond Qll. It works like the diode across the pinball
coil. It will run awhile and blow your Qll again.
I HAVEN'T SEEN ANY OF THIS PUBLISHED BEFORE ...
Well, it's not the preferred method!
CAN YOU MEASURE TIIE C36 CAP ON CHASSIS, OR DO
YOU HAVE TO PULL IT?
It's best to pull it to test it-it's a feed-through and a
Thank you, James Beck.
Note: See page 2 l for STAR*TECH Journal's updated list of
music and game manufacturers customer service phone and fax numbers
Also, the Area Code Decoder has been updated with new codes.
-------------------17-------------------
So IF TIIE PICTURE TUBE GOES, IT JUST DOESN'T DO ITS
JOB, AND IT USUALLY DOESN'T TEAR TIIE BOARD DOWN
WITII IT?
Exactly.
IN TIIE CASE OF A SUSPECTED BAD FLYBACK, CAN YOU
1'._""rAR TECH JoURNAL
capacitor- the two right end legs are connected to-
gether and the two left end legs are connected to-
gether, with the capacitor in the middle. It acts as a
fuse and a safety cap. If the voltage goes too high
or the current goes too high, that cap blows. Note:
Some models DON'T use the 4 lead caps.
DISCONNECT THE HORIZONTAL OUTPUT'S COLLECTOR
LEAD AND POWER UP TIIE CHASSIS TO SEE IF TIIE OTIIER
COMPONENTS ARE ALL GOOD?
No, because too many of the
voltages are coming through
there that are needed for the
chassis to come up. Every-
thing but the AC derived
power would be dead if you
did that.
So
WHAT DO WE MEASURE TIIERE?
Infinity. If you measure any
resistance, it's shot. Replace it.
WHAT OHM READING DO WE
WANT ACROSS PINS
1 AND 4 OF
fflE VOLTAGE REGULATOR?
150 to 220 ohms you might ex-
pect, but it varies by meter
model.
HOW DO YOU MEASURE A
BAD FLYBACK? CAN YOU ISO·
AND WHAT'S ACCEPTABLE MEA·
LATE IT?
SUREMENT OF Qll?
You can measure if the pri-
mary windings are shorted
together normally you'll mea-
sure a handful of ohms,
maybe 2 or 3. If you're into
zero or 1 ohm, you've got a
problem ... But on the 7000's
they're notorious for blowing
the safety capacitors.
With no power and in the di-
ode test mode, you should see
similar measurements of in-
creasing ohms -just as if you
were reading across an 1N4004
diode.
So,
WE SHOULD READ ONE OF
fflOSE TO GET A BETTER IDEA OF HOW OUR METER READS
DIODES IN fflE DIODE MODE AND RESISTANCE MODE.
Is TIIAT C36?
Yes, and C39. And all that stuff on the schematic
under the flyback-you've got a handful of diodes
and a couple of caps-any of that stuff will blow your
fuse.
Also, D18 needs to be replaced if you blew a sec-
ond Qll. It works like the diode across the pinball
coil. It will run awhile and blow your Qll again.
I HAVEN'T SEEN ANY OF THIS PUBLISHED BEFORE ...
Well, it's not the preferred method!
CAN YOU MEASURE TIIE C36 CAP ON CHASSIS, OR DO
YOU HAVE TO PULL IT?
It's best to pull it to test it-it's a feed-through and a
Thank you, James Beck.
Note: See page 2 l for STAR*TECH Journal's updated list of
music and game manufacturers customer service phone and fax numbers
Also, the Area Code Decoder has been updated with new codes.
-------------------17-------------------
Future scanning projects are planned by the International Arcade Museum Library (IAML).