April 1994
"'krAR TECH JOURNAL
MONITOR REPAIR FOR DUMMIES:
WELLS GARDNER
7000
CHASSIS
BUFFALO BILL PUMPS STAR TECH'S JAMES BECK FOR REPAIR TIPS:
Bill Johnston
Johnston Video
Buffalo, New York
.
James Beck
Bbs Sysop
STAR*TECH Journal
(Use of the information from the following conversation requires advance level bench technician
experience and a safe non-conductive work area, applying power to the chassis through an
isolation transformer, and sometimes, good reflexes.)
CAN YOU POWER UP TIIE CHASSIS WITIIOUf CONNECT·
How DO YOU KNOW WHEN A PICTURE TUBE IS BAD-
ING IT TO A PICTURE TUBE?
WHAT DOES IT DO TO TIIE CHASSIS?
Yeah.
Bur WHAT ABOUT TIIE IDGH VOLTAGE LEAD?
I usually tape the high voltage anode lead to the
table faraway from me, and if the tape comes loose,
just get out of the way! The yoke needs to be con-
nected on some models for the chassis to power up,
but most 7000's tend to power up even without the
yoke. It varies by submode!.
WHAT'S TIIE HAZARD TO 111.E CHASSIS IF YOU DON'T
PLUG IN TIIE YOKE?
No hazard-it may just go into shutdown.
WHAT ABOUT NO NECKBOARD BEING CONNECTED?
You can still power it up- it will still run.
Usually, I know the picture tube is bad when you're
missing one color and you can't get it to come up by
grounding out the problem gun.
IF YOU CAN'T GET IT UP BY SWAPPING TIIE VIDEO COLOR
LEADS FROM TIIE GAME BOARD?
No, you don't even have to do that-here's a way to
test the tube directly: Take an insulated alligator
clip lead, ground one end to the chassis, and touch
the other end to the drive transistor on the neck
board's collector, which is the tab. That'll kick that
color wide open, as bright as it can go. If you touch
the bad one and it's dim, it's suspected bad. If you
touch one and it brings up the wrong color, there's
a short. The easiest way to check a tube is with a
picture tube analyzer. And rejuvenate away!
AND TIIE SCHEMATIC VOLTAGES?
How CAN YOU MEASURE WHETHER A PICTURE TUBE IS
They'll be a little high, especially the B+ and fo-
cus-but you won't be poking at that with your fin-
gers!
BAD? OR DOES IT HAVE TO BE IN CIRCUIT?
It has to be in operation, because of the voltages
involved. A CRT analyzer does a fairly good job of
simulating operation.
WILL B+ FLOAT UP TO SHUTDOWN VOLTAGE?
No, they've got pretty good regulators on there.
That's the reason why they'll run without a yoke. If
it's got a good regulator it will usually
power up.
Is TIIERE
A SHORT IN TIIE TUBE TIIAT WILL CAUSE m
FUSE TO BLOW OR A FAILURE OF OTIIER COMPONENTS?
For all practical purposes, No.
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