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CIRCUIT DESCRIPTION
VOLTAGE LOSS DETECTION
1. Shorted 220V (DP31 and DP32) Inverted by QP03 then through DP22
2. Shorted SW+8V (DP33) Inverted by QP03 then through DP22
3. Shorted 28V (DP30) Inverted by QP03 then through DP22
4. Shorted Side Pin Cushion Circuit (D760 and Q754) then through DP34
5. Shorted Deflection Transformer or Erroneous (D756 and Q754) then through DP34
6. Heater Loss Detection (DH26, DH27, QH07 and DP34) this voltage does not go to the CRTs.
NEGATIVE VOLTAGE LOSS DETECTION
7. -M28V Loss Detection (DP23, DP24)
8. SW-8V Loss Detection (DP28, DP29)
EXCESSIVE CURRENT DETECTION
9. 120V Deflection Power Supply (RP17, QP02, DP15, DP16 and DP18)
10. 28V Vertical IC I601 Power Supply (R645, Q609, D615, and DP34)
Voltage Too High Detection
11. Excessive High Voltage Detection (DH31, RH54, RH55 and DH24) Sensed from the Heater Voltage
generated from pin (5) of the Flyback Transformer TH01. Also, (DH42) sends a high command to the
Horizontal Driver IC IH02, to defeat Horizontal Drive Output.
12. Side Pincushion failure generating a High. (D754, and D753).
13. Deflection B+ Too High. (DP17, RP21 and RP22)
14. Heater Voltage from the Deflection Power Supply Too High Detection. (DP27 and DP28)
If any one of these circuits are activated, the power supply will STOP, and create a Power Supply Shut-
down Condition.
SHUT DOWN CIRCUIT:
Shut down occurs when the shutdown SCR QP01 is activated by gate voltage. When QP01 receives gate
voltage of 0.6V, the SCR fires and give a ground path for the pin (5) of Connector PQD2 called PRO-
TECT. This low is routed to the Sub Power Supply PWB and is impressed on the base of the Relay Driver
Transistor Q911 turning it off. When Q911 turns Off the Relay S901 will disengage and remove the AC
source from the Deflection Power Supply.
DESCRIPTION OF EACH SHUT DOWN CIRCUIT:
Please use the Commonly Used Shutdown Detection Circuits for the description of how the circuit works.
VOLTAGE LOSS DETECTION
1. Shorted 220V (DP31 and DP32) Inverted by QP03 then through DP22
The cathode of DP31 is connected directly to the 220V line. If it shorts this circuit is activated and pulls the
base of QP03 low. This output high is routed through DP22 to the gate of the Shut down SCR QP01.
2. Shorted SW+8V (DP33) Inverted by QP03 then through DP22
The cathode of DP33 is connected directly to the SW+8V line. If it shorts this circuit is activated and pulls
the base of QP03 low. This output high is routed through DP22 to the gate of the Shut down SCR QP01.
3. Shorted 28V (DP30) Inverted by QP03 then through DP22