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5Vdc = ballast / lamp-on) command but does not receive a lamp-on response (B2/pin 3
= 0Vdc) within 4 seconds, the microprocessor terminates the original ballast-on
command. After 38 seconds, the ballast / lamp-on command is repeated, in an attempt
to re-trigger the failed lamp. However, if the lamp fails to ignite in the second attempt,
the TV turns off in about 50 seconds.
Testing the Lamp & Ballast
If the lamp does not ignite, the microprocessor mutes both the audio and video signals.
The problem is either in the lamp, the ballast, or the lack of turn-on signal to the ballast
(from the microprocessor on the DG board). There are simple ways to test the (1) lamp,
(2) ballast, and (3) microprocessor output.
1. Lamp Test:
If the lamp has broken glass or a broken electrode, a sound is heard when the lamp is
shaken. Replace the lamp if something is loose in the lamp assembly.
2. Ballast Test:
Refer to figures 19 and 20. You can test the Ballast by either (a) watching the Z001
Z 001
See figure 20
Figure 19 - TV rear view (bottom)
spark gap device glow, proving that the ballast can develop HV or (b) by bypassing the
microprocessor and manually turning on the ballast to ignite the lamp.
a) Ballast test 1 - Spark gap device glow – Refer to figure 19. Remove the rear bottom
cover to expose the electronics.
Locate the ballast assembly (in a perforated shield
enclosure). The perforated cover has been removed in figure 20 for clarity. Do not
remove the perforated shield.
Plug the TV in and turn it on while watching Z001. If the ballast and microprocessor are
working, the Z001 spark gap will glow while arcing (frying noise), proving that the ballast
is OK and the lamp is bad.
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