Sony KV-13FS100 Product & Training Manual page 15

NOTE: Use HOT GRND when making measurements on primary side of T603. This includes all measurements
on IC600.
Symptom: Unit goes into protection mode LED flashes four times.
Check: This indicates either a Vertical deflection or Power Supply problem.
1) Check power supply secondary outputs.
•
If voltages are present and at the proper level, then the problem is in the Vertical deflection drive
circuit.
•
If the secondary voltages are low or missing, then the problem is in the power supply.
2) The power supply can be safely tested by unloading the +135v line. Unsolder R591. This will unload the
+135V line of the power supply, but still send needed feedback to IC600 for proper power supply operation.
3) If the power supply outputs proper secondary voltages after unsoldering R591, suspect a shorted +135V
line. Check the Horizontal Output transistor (Q505 or 506) for shorted conditions.
4) If the unit still goes into protection mode after unsoldering R591, check the following items:
•
D614 for shorted condition.
•
IC600/pin 15 (this is midpoint for output MOSFETS Q600 and Q601). A 275Vpp, 85KHz square-
wave should be present. If the waveform pulses four times and stops, check the next Item.
•
IC600 Feedback circuit. The amount of current feedback can be determined by monitoring the
voltage drop across R625. The minimum current feedback is 80uA, which is a minimum voltage
drop of 37.6mV. In normal operation, this voltage drop is approximately 223mV. If the voltage
drop is below 37.6mV, suspect components in the feedback path e.g. PH602 and IC604. Reference
Figure 3-3 for proper voltages at these components.
•
If no waveform is present when unit is turned ON, then check IC600/pins 1 and 18 for proper
voltages (reference "IC600 Startup Sequence" above).
If these voltages check OK, check IC600/pin 8 for proper voltage of 24V. This is the voltage used
to power IC600 after initial startup.
If 24V is present at IC600/pin8, check IC600/pin 10 for 10.2V. This voltage is developed using the
24Vs and a voltage regulator circuit inside IC600. If 10.2V is missing, suspect a defective IC600.
Also check voltage at IC600/pin 14 (Use battery powered VM for this measurement, and use
IC600/pin 15 (VS) as ground ref.). The voltage at IC600/pin 14 should be 10V. If the voltage
measured at IC600/pin 14 is incorrect, check D618.
•
If all the above measurements check OK, suspect a defective IC600.
5) Defective Output MOSFET transistors: The output MOSFETS will cause a "no output square-wave"
condition. To properly test MOSFETS, reference the following test procedure:
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3. Power Supply Block