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HOT GROUND SIDE SHUT DOWN SENSING CIRCUITS
(INTERNAL TO IP01)
LATCHED SHUT DOWN MONITORS
(AC must be removed to recover)
1. Pin 4 is monitored for Over Voltage internal to
IP01.
2. IP01 itself is monitored for Excessive Heat. This
block is labeled T.P.O. (Thermal Protection Over-
load).
RECOVERING SHUT DOWN INPUT
(Driver IC will recover on it's own when trouble is
removed)
3. Pin 5 besides being used as a regulation input, it
also monitors low ohm resistors RP10, RP11, RP12,
and RP16, (All are 0.22 ohm resistors). If these
resistors have an excessive current condition
caused by monitoring the current through the in-
ternal Switch MOS FET, the voltage will rise. Pin 5
has an internal Over Voltage detection op-amp. If
this voltage rises enough to trigger this op-amp,
the IC will stop producing a drive signal.
COLD GROUND SIDE SHUT DOWN CIRCUITS
These Circuits are broken down into the appropriate
categories as described earlier.
VOLTAGE LOSS DETECTION
1. Shorted 220V (DP24 and DP25) Inverted by QP03
then through DP28
2. Shorted SW+35V (DP26) Inverted by QP03 then
through DP28
3. Shorted 28V (DP27) Inverted by QP03 then
through DP28
4. Shorted Deflection Transformer or Miss-operation
(D707 and Q705) then through D705
NEGATIVE VOLTAGE LOSS DETECTION
5. -28V Loss Detection (RP21, RP20, DP35, DP21 and
DP22)
EXCESSIVE CURRENT DETECTION
6. 115V Deflection Power Supply (RP24, QP02, DP18,
DP19 and DP20)
7. 28V Vertical IC I601 Power Supply (R629, Q609,
D608, and DP31)
VOLTAGE TOO HIGH DETECTION
8. Excessive High Voltage Detection (DH17, DH13 and
DH15). Sensed from the 50P Voltage generated
from pin (5) of the Flyback Transformer TH01. Also,
(DH14) sends a high command to the Horizontal
Driver IC IH01 pin 7, to defeat Horizontal Drive
Output if this voltage goes too high.
9. Side Pincushion failure generating a High. (D702,
and D703).
PV154 - 923-03506
CIRCUIT DESCRIPTIONS
If any one of these circuits are activated, the power
supply will STOP, and create a Power Supply Shut down
Condition.
SHUT DOWN CIRCUIT DESCRIPTIONS
Shut down occurs when pin (1) of Connector PQD2 called
PROTECT goes High. This High is routed to the Sub Power
Supply PWB and is impressed on the base of the Relay
Driver Transistor Q916 turning it On. When Q916 turns
On, it removes the Power On High and the Relay S901
will disengage and removes the AC source from the De-
flection Power Supply.
Please use the Commonly Used Shut down Detection Cir-
cuits for the description of how the circuit works.
3-3
10. Deflection B+ Too High. (DP17, RP26 and RP27).
11. SW +9V Voltage Too High Detection. (DP29 and
DP30)
12. ABL Voltage Too High Detection. (DH15)
VOLTAGE LOSS DETECTION
1. Shorted 220V (DP24 and DP25) Inverted by QP03
then through DP28. The cathode of DP24 is con-
nected 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 DP28 to
pin (1) of Connector PQD2 called PROTECT and Shut
Down occurs as described above.
2. Shorted SW+35V (DP27) Inverted by QP03 then
through DP28. The cathode of DP27 is connected
directly to the SW+35V line. If it shorts, this cir-
cuit is activated and pulls the base of QP03 low.
This output High is routed through DP28 to pin
(1) of Connector PQD2 called PROTECT and Shut
Down occurs as described above.
3. Shorted 28V (DP27) Inverted by QP03 then
through DP2. The cathode of DP27 is connected
directly to the 28V line. If it shorts, this circuit is
activated and pulls the base of QP03 low. This
output High is routed through DP28 to pin (1) of
Connector PQD2 called PROTECT and Shut Down
occurs as described above.
4. Shorted Deflection Transformer or (D707 and Q705)
or D705. The Deflection circuit generates the ac-
tual Drive signal used in the High Voltage sec-
tion. If a problem occurs in this circuit, the CRTs
could be damaged or burnt. D707 is connected to
R728 which normally passes the same pulse as used
for generation of the H. Blanking signal. This pulse
is generated off the Deflection Transformer T752.
The pulse is rectified by D707. This rectified volt-
age is normally sent to the base of Q705 keeping
it On and its collector Low. If the Deflection cir-
cuit fails to produce the pulses for rectification,
the base voltage of Q705 disappears and the tran-
ZP26/28 - SERVICING
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