Star Tech Journal

•
July 1992
Figure 4 (Flyback Circuit:
STAR*TECH Joumal
·x· Marks the Primary)
to yoke
horizontal output
transistor
- -
C
f
~
----/
expect to see half the waveform (Figure 5b). When
in doubt check your reading against a known good
part or chassis.
Ifi t fails to allow a peak, then steps should be taken
to localize the problem. First disconnect the collec-
tor of the output transistor. This can often be done
by just removing the mounting screws. Each time
you disconnect anything, re-check the circuit to see
if the short is gone.
It's a good idea to take about 90 seconds at this
point and check any diodes on scan-derived sup-
plies -basically any diode tucked away in the
flyback area. Again, you are looking for that diode
waveform of figure 5b. Any diode that reads as a
direct short should have a lead lifted and be
retested. Al though a shorted diode will tend to pull
down the readings on all of these in circuit, there is
~often a subtle difference between the short and
other diodes.
~
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Don't allow this test to take up very much time,
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r •
•
~
'7---'f
PATT SUPPLY CORPORATION
1335 S. MICHIGAN AVE. CHICAGO. IL 60605
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