![background image](http://html.mh-extra.com/html/zenith/iqc50h94/iqc50h94_technical-training-manual_929556004.webp)
2
PRODUCT SAFTEY
CHASSIS HIGH VOLTAGE ADJUSTMENT
PROCEDURE
1. Connect High Voltage meter to FBT High
Voltage output. Connect Ground of High Voltage
meter to CRT Ground or FBT Ground.
2. Check that the High Voltage adjustment VR
(RH44) is set to its mechanical center on the
Deflection PWB. This VR is located just behind
the Flyback transformer as viewed from the
Front of the set. (See diagram below)
3. Receive an NTSC generator signal. (Picture
should be stationary for this adjustment.
4. Video Controls should be set to Factor Settings.
5. Adjust the High Voltage to the following specifi-
cations by turning RH44 slowly.
6. Lock Paint the control. If available.
CHASSIS HIGH VOLTAGE LIMITER
CHECK
Check Preparation:
1. The set can face any direction.
2. Receive the Cross-Hatch Signal
3.
VIDEO CONTROLS:
Brightness to Maxi-
mum.
4.
SCREEN FORMAT:
Should be
PROGRES-
SIVE
mode.
5. Attach the JIG (1k ohm 1/8W resistor) to both
ends of DH31 as shown in the diagram below.
(See Diagram)
Checking Procedure :
1. Check that the picture is turned off and the
horizontal deflection circuit stops operation.
After Checking:
1. Unplug set and Remove Jig. Allow set to remain
in the off condition for at least 15 seconds.
2. Apply AC and confirm the set returns to normal
operation.
CHASSIS FLYBACK PROTECTION
CIRCUIT CHECK
Check Preparation:
1. The set can face any direction.
2. Receive the Cross-Hatch Signal
3.
VIDEO CONTROLS:
Factory Preset.
4.
SCREEN FORMAT:
Should be
PROGRES-
SIVE
mode.
5. Attach a 100 K ohm 1/16W ~ 1/8W resistor
between QP02 base and Gnd. (SD4 connector
Pin 4) and check operation.
After Checking:
1. Unplug set and Remove Jig. Allow set to remain
in the off condition for at least 15 seconds.
2. Apply AC and confirm the set returns to normal
operation.
RH44
High Voltage ADJ.
FBT
TH01
RH54
RH55
CH30
DH31
DH24
+50V Pulse
Add JIG to check Hi
Volt Limit Circuit
JIG = 1k ohm 1/8W