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Rob Moffatt
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PostPosted: Mon Dec 10, 2007 1:14 am    Post subject: KV34XBR800 Reply with quote

KV34XBR800 DA-4 Chassis. Set displays a four blink error code. Checking the following components netted the following voltages from around the Horiz Output Xformer, T5001.

Q5003 (PWM-OUT) IRFI9630G-LF
G= +130V
S= +133V
D= +72V

IC5004 (vert output) STV9379
Pin1= +0.6V
Pin2= +15.8V
Pin3= -9V
Pin4= -9.7V
Pin5= -8.4V
Pin6= +15V
Pin7= +0.6V

IC5005 (Horiz Cent) LA6500-FA
Pin1= +72V
Pin2= +72V
Pin3= +73V
Pin4= +75V
Pin5= +105V

there is a raster in the lower half of the screen when G2 is advanced which appears to be folded over and rolling, the raster is also narrow as if a lack of B+. Swapping out IC5004 (vert output) made no change. Any idea why "d" voltage on Q5003 is 72volts instead of 10 as the service lit suggests??? Any help is greatly appreciated as I believe these boards are now NLA as an assembly.

Rob
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minnie



Joined: 18 Aug 2005
Posts: 2877
Location: Hell

PostPosted: Mon Dec 10, 2007 8:11 pm    Post subject: Reply with quote

Troubleshooting Tips (ref. Figure 3-3)
NOTE: Follow previously discussed “IC6501 Startup Sequence”. The five steps are in order of occurrence.
NOTE: Use HOT GRND when making measurements on primary side of T6502. This includes all
measurements on IC6501.
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 proper the 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 R5013. This will unload
the +135V line of the power supply, but still send necessary feedback to IC6501 for proper power supply
operation.
3) If the power supply outputs proper secondary voltages after unsoldering R5013, suspect a shorted +135V
line
4) If the unit still goes into protection mode after unsoldering R5013, check the following items:
· D6538 (5V Zener) for shorted condition.
· Check IC6505 (B+ OVP) for proper operation.
· IC6501/pin 15 (this is midpoint for output MOSFETS Q6507 and Q6506). A 275Vpp, 85KHz
square-wave should be present. If the waveform pulses four times and stops, check the next
Item.
· IC6501 Feedback circuit. The amount of current feedback can be determined by monitoring the
voltage drop across R6525. 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. PH6502 and IC6503.
Reference Figure 3-3 for proper voltages at these components.
· If no waveform is present when the unit is turned ON, then check IC6501/pins 1 and 18 for proper
voltages (reference “IC6501 Startup Sequence” above).
If these voltages check OK, check IC6501/pin 8 for proper voltage of 24V. This is the voltage
used to power IC6501 after initial startup.
If 18V is present at IC6501/pin8, check IC6501/pin 10 for 10.2V. This voltage is developed using
the 18Vs and a voltage regulator circuit inside IC6501. If 10.2V is missing, suspect a defective
IC6501. Also check voltage at IC6501/pin 14 (Use battery powered DVM for this measurement
and use IC6501/pin 15 (VS) as ground ref.). The voltage at IC6501/pin 14 should be 10V. If the
voltage measured at IC6501/pin 14 is incorrect, check D618.
· If all the above measurements check OK, suspect a defective IC6501.
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PostPosted: Wed Dec 12, 2007 11:52 pm    Post subject: Reply with quote

many thanks mini!! the power supply voltages were all within tolerance and I'm now concentrating once again on the drive/output circuit.
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Rob Moffatt
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PostPosted: Wed Dec 12, 2007 11:57 pm    Post subject: Reply with quote

minnie* sorry about that.....

Rob
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