S
B. Defective diode off the flyback.
C. Defective focus control.
D. Defective picture tube (CRT).
4. Picture not bright enough:
A . If the CRT voltages are present, the picture
tube is probably bad. The surest way to
cure this on an X-Y monitor is to replace
the picture tube (CRT).
B. Weak 90 volt supply from the EHT power
supply.
C. Loose wire to socket of CRT for G2
voltage.
12. Hazy blob of light that shimmers on the
screen:
A. Open secondary on flyback winding.
B. Failure of some. component in the high
voltage section.
13. Corners of the picture are missing: :
A. Yoke is too far back on the picture tube
neck.
14. Picture is too far up, down, or not centered
properly:
A. Metallic yoke tabs need to be adjusted.
15. A shadowy image of the game remains on the
screen, even after monitor is off:
5. Silvery effect to the white lines, or picture
A. Picture tube has burnt phosphor.
looks dim, washed out:
A. If the CRT voltages are present, the picture
tube is probably bad. The surest way to 16. 2-amp fuses keep blowing:
A. Check the large heat-sinked power tran-
cure this on an X-Y monitor is to replace
sistors.
the picture tube (CRT).
B. Check D608 and D708.
6. Increasing brightness causes an increase in
C. Check semiconductors, especially the
picture size and weakens focus:
transistors in the "X" and " Y" amplifiers.
A. For the most part, this is normal in X-Y
D
.
Bad
yoke.
monitors. But if this should occur at normal
viewing levels, either:
17. Video information is distorted; letters and
• The CRT is defective.
figures are "crinkly"-like crumpled paper,
• The high voltage rectifier is weak.
and it shakes slightly:
• Or the high voltage circuitry has poor
A. Bad 90 volt power being supplied by the
regulation.
EHT unit. If everything looks good, check
the electrolytics.
7. Picture rapidly blinks on and off:
A. Internal short in the picture tube ( arcing).
B. The regulator control (R905) may need
8. A dot on the middle of the screen-Red LED
is turned on Oocated on the deflection board):
A . The"X" and "Y" signals are not making it
into the monitor.
B. Check cabling, jacks, and logic boards.
C. "X" and "Y'' amplifier failure. See Number
1 above and check the fases first.
9. Monitor won't turn on:
A . Open fuse(s).
B. A
•
•
•
defect in the power supply; check:
Fuse(s).
Transistors.
Open fusible resistor.
C. Check jack to make certain all pins are
obtaining their voltage from the other
game circuitry.
D . Check for loose foil, especially by DlOO.
10. Blown 5 amp fuses:
A. Caused by bad luck. Change fuses.
B. If they keep blowing, check all power
transistors that are heat-sinked on the side
(as in the 19" version) or the bottom (as in
the l 3" version) of the monitor.
11. Extremely bright picture; spider-web like
retrace lines floating around on the picture:
A . Defective "Z" amplifier circuitry; check:
• The brightness and contrast controls.
• For peeled foil on the deflection board.
• Semiconductors, etc.
B. See symptom 4, diagnosis "B" and "C"
ONLY. A bad EHT power supply or loose
G2 wire can cause the same thing.
adjusting.
• On the Wells Gardner monitor, the
anode voltage is supposed to read
14.SKV High Voltage. That's 14,500
volts with the beam current at zero.
R905 adjusts this output voltage. To
read this voltage, your meter needs a
separate high voltage probe. Follow the
directions EXACTLY as stated with
the literature that comes with the probe.
If you don't, or you touch something
you shouldn't, you're dead. If this scares
you, have someone qualified ( a techni-
cian) perform this adjustment for you.
Better SAFE than sorry.
• In the case of the Electrohome monitor,
the adjustment is complex and, of course,
potentially DANGEROUS. Basically,
the Electrohome anode voltage from
the "flyback" and rectifier is supposed
to be set at 12,000 volts with the beam
current at zero. That's right -
THOUSANDS of volts! To read this
voltage, your meter needs a separate
high voltage probe. Follow the directions
EXACTLY as stated with the literature
that comes with the probe. If you don't
or you touch something you shouldn't,
you're dead. If this scares you, have
someone qualified ( a technician) perform
this adjustment for ·you. Better SAFE
than sorry.
If you are still unsure, it may be best if
you call Electrohome at (519) 744-
7111 and obtain exact information from
one of their staff engineers.
* TJ FEBRUARY 198215
*
EDUCATION
is the key to success in
any technical career and
especially the pinball and
video game repair
business. Now you can
learn - not only practical
know-how - but also a
solid background in
electronics and
microprocessor
technology. This
knowledge will enable
you to keep abreast of
this fast changing
business. At E.I.B. we
offer courses at all levels.
Day and eve~ing courses
available.
For further
information
& application:
*
ELECTRONIC
INSTITUTE
OF BROOKLYN
4823 Ave. 'N'
Brooklyn, NY 11234
*
*
212/377-0369
(collect)