Sony KV-32HS500 Training Manual page 27

UVP – less then 8V
If either of these two conditions occurs at IC6501/pin 8, the unit will go into protection mode. The self-
diagnostic indicator will flash four time times, pause and then repeat.
Troubleshooting Tips (ref. Figure 3-3)
NOTE: Follow previously discussed "IC6701 Startup Sequence". The five steps are in order of occurrence.
NOTE: Use HOT GRND when making measurements on primary side of T6703. This includes all
measurements on IC6701.
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.
2) If voltages are present and at the proper level, then the problem is in the Vertical deflection drive circuit.
3) If the secondary voltages are low or missing, then the problem is in the power supply.
4) The power supply can be safely tested by unloading the +135v line. Unsolder l6514. This will unload the
+135V line of the power supply, but still send necessary feedback to IC6701 for proper power supply
operation.
5) If the power supply outputs proper secondary voltages after unsoldering l6514, suspect a shorted +135V
line. Check the Horizontal Output transistor (Q505 or 506) for shorted conditions.
6) If the unit still goes into protection mode after unsoldering lC6514, check the following items:
•
IC6701/pin 15 (this is midpoint for output MOSFETS Q600 Q6701 and Q6702). A 275Vpp, 78KHz
square-wave should be present. If the waveform pulses four times and stops, check the next
Item.
•
IC6701 Feedback circuit. The amount of current feedback can be determined by monitoring the
voltage drop across R6732. 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 3-7 for proper voltages at these components.
•
If no waveform is present when unit is turned ON, then check IC6701/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 18V. This is the voltage used
to power IC6701 after initial startup.
If 18V is present at IC6701/pin8, check IC6701/pin 10 for 10.2V. This voltage is developed using
the 18Vs and a voltage regulator circuit inside IC6701. If 10.2V is missing, suspect a defective
IC6701. Also check voltage at IC600/pin 14 (Use battery powered DVM for this measurement,
and use IC6701/pin 15 (VS) as ground ref.). The voltage at IC6701/pin 14 should be 10V. If the
voltage measured at IC6701/pin 14 is incorrect, check D6712.
•
If all the above measurements check OK, suspect a defective IC600.
3. Power Supply (DA-4 & DA-4X Chassis)
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