Ballast Circuit; Lamp On Sequence Chart; Ballast Board Layout; Ballast Board Requirements - Panasonic PT-50DL54 Technical Manual

Ballast Circuit

This chapter of the book is divided into 6 sections:

1. Lamp On Sequence Chart

2. Ballast Board Layout

3. Ballast Board turn-on voltages
Lamp On Sequence Chart
1 Press the power-on button.
The TV's microprocessor turns on the
2
ballast power supply stage on the P power
supply board.
3 The Microprocessor initiates a ballast turn-
on command. (5 seconds after power-on
button is pressed.)
4 The ballast circuitry generates over 20kV to
ignite the lamp.
5 The ballast control circuit grounds B2/pin 3
to inform the microprocessor that the lamp
is drawing current (lamp turned on).
6 Press the power-off button.
7 The Microprocessor ballast turn-on
command goes low. A/V is muted.
8 Ballast stops the 20kVac supply to the lamp.
Microprocessor keeps fans running for 20 seconds longer, and then shuts the TV off.
9
Ballast Board Layout
Signal Name
+335Vdc supply
voltage
No connection
Floating ground

Ballast Board Requirements

Refer to tables 10 & 11. The ballast assembly produces HV for the lamp when the two
voltages listed in table 11 are input. Notice that the ballast operates, using hot ground
but a cold ground microprocessor signal is also needed.
Lamp On
Operation
Lamp Off
Ballast Board Connectors
B1 Connector
Input /
Output
In
In
Table 10
4. Ballast Block Operation
5. Testing the Lamp and Ballast
6. L Board LED Indicators
Voltage
Stby 7Vdc TP on PS bd. next to P4
+335Vdc Ballast Bd. B1/pin 1. Use Pin 3
or CN005 as (floating) ballast
ground.
2Vdc Ballast Bd. B2/pin 1.
(High) Use chassis ground or pin 2
(cold ground).
20kVac Lamp On (ignition). Low to full
brightness in 1 minute.
0Vdc Ballast Bd. B2/pin 3.
Use (cold) chassis ground.
0Vdc Ballast Bd. B2/pin 1.
Use (cold) chassis ground.
Lamp goes off.
Table 9
Pin Signal Name
1 Ballast-On from
microprocessor
2 Cold ground
3 Lamp On
23
Test Location / Verification
B2
Input /
Output
In
In
Out