6-100
7. Check the test waveforms shown for schematic diagram 21 (waveforms 159 through 168).
Troubleshoot the circuitry indicated by an incorrect waveform (see the following troubleshooting
procedures).
5. Check that U524A pin 5 has a positive pulse coincident with the ATHO transitions. Check that
U524A pin 3 is HI. If pin 3 is HI and pin 5 does not follow the ATHO transitions, replace U524.
6. Check pin 8 of U524B for a negative (TVTG) pulse coincident with the LO-to-HI ATHO transitions.
If not present, check that the TVENA signal on pin 12 is HI and that the HORIZCLK input on
pin 11 (see waveform 163) is ok. If those signals are correct, replace U524; if not correct, trouble-
shoot the source of the problem.
4. Check that U541B pin 6 has a positive pulse coincident with ATHO transitions. If not, replace
U541.
3. If the ATHO signal is ok, check U424C pin 6 for an inverted ATHO signal; if not present, replace
U424.
2. If signal is absent, check the ATHO signal line at U424C pin 5 for HI-to-LO and LO-to-HI transi-
tions. If not there, troubleshoot the Holdoff circuit (schematic diagram 13) as indicated in Table 6-6
in "HOLDOFF PROBLEMS".
1. Check the TVTG signal at U524B pin 8. If signal is present and no triggering is occurring, trouble-
shoot the Trigger Logic Array, A1OU370(schematic diagram 11).
TV LINE
OFF
A TV COUPLING
CLAMP
Press SET TV and select:
- (negative sync)
CH 2
AUTO LEVEL
TV
CH 2
20
ILS
o
(no HO symbol displayed)
1 V
SLOPE/SYNC
VERTICAL MODE
TRIGGER MODE
TRIGGER CPLG
TRIGGER SOURCE
SEC/DIV
A TRIGGER HO
VOLTS/DIV
Set the following controls:
Apply a negative-sync, flat-field, video signal to the CH 2 input. Select the correct protocol (System M
or Nonsystem M) for the applied signal using the Extended Functions menus.
INITIAL SETUP:
Auto triggering or unstable trigger in TV CPLG:
TV TRIGGER
PROBLEM
Table
6-7
(cont)
Maintenance-2430 Service
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