Sony KV-32HS500 Training Manual page 30

4. DA-4 & DA-4X Protection Circuits
The important thing to note on this diagram is the protection circuits that have a direct connection to the CPU and
those that do not. The protection circuits that have a direct connection will produce a more reliable flash sequence
e.g. 2X, 3X, 4X, and 6X. The circuits that do not have a direct connection may produce a 7X or 6X flash
sequence.
TH5002 is used to monitor the temperature of Q5031 (S-Correction Output). If this transistor should become a
short circuit, the current will increase which causes an increase in temperature. TH5002 detects the rise in
temperature, the Video is muted and AC input is disconnected through IC2801 (CRT Drive) and data
communications with IC2300 (Syscon).
Q5004 monitors the current draw on the +135V line. If the current should increase, video is muted via IC2801
and IC2300. Also note that there is a direct connection from the B+ OCP circuit and IC2300 Syscon for quick
disconnection of AC input.
Q8008 monitors the current in the secondary of the FBT using the ABL voltage. If excessive current flows in the
FBT, Q8008 is used to mute the video. Q8008 works simultaneously with Q8007, which turns off the AC relay.
IC5004 is the vertical deflection output drive IC. A feedback pulse is produced at IC5004/pin 3. If a vertical
failure occurs, the feedback pulse is not produced and the video is muted (AC input and Audio remain ON).
Q2314 monitors the 5V dc level. If the dc level falls below 4.5V, Q2314 detects this error and the AC input is
disconnected.
IC9001, 9002, and 9003 on the CH/CX board are the cathode drive ICs. Each IC produces a separate IK pulse
directly proportional to the current in each cathode. The current in each cathode indicates the physical condition
of the cathode. Depending on the cathode condition the set will either increase RGB drive to the cathode or go
into IK Protection mode.
RY6502 is used to bypass the Inrush Current resistor from the AC input circuit after initial set turn-on. If the relay
failures to activate, AC input is disconnected.
IC8006 monitors the HV output. If the HV is low, IC8006 detects this condition and the AC input is disconnected.
IC6505 monitors the +135 voltage level. If the voltage increases, IC6505 will disconnect the AC input.
Q8007 monitors the current in the FBT secondary. If the current increases, Q8007 will disconnect the AC input.
Q8007 works simultaneously with Q8008, which mutes the video output.
IC8001 monitors the HV level. NOTE: this circuit is on the HOT (or primary) side of the transformer, so use
HOT Ground for measurements. If the HV increases, IC8001 will turn off the HV converter IC8002.
IC8006 monitors the horizontal deflection output drive. If the horizontal deflection stops, IC8006 will turn-off the
HV converter IC8002.
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