Sony TV model# KV-21GMR1 is a dead set: no LED standby indicator light, +115V supply to horizontal output transistor measured only 27V and is pulsating.
The SMPS regulator IC STR-S6707 was replaced but still the +115v supply line is dropped.
Even when the horizontal output transistor is disconnected from the circuit the +115V supply will not increase.
An ohmmeter check on the SE115N error amplifier shows that it is internally open circuited.
Power was restored to the set when the SE115N was replaced.
Showing posts with label Sony TV repair. Show all posts
Showing posts with label Sony TV repair. Show all posts
Thursday, June 16, 2011
Friday, November 26, 2010
Sony TV KV-25JXR20 reduced horizontal width problem
The owner of a Sony TV with model number KV-25JXR20 complained of the reduced horizontal width of the picture of his TV. He also observed "blinking" of the picture which must be his description of intermittent blanking of the picture.
During my initial observation of the problem I also noticed that the vertical size of the picture is in overscan - or stretched - resulting to vertical mislinearity and the presence of red, blue and green blanking lines at the top edge of the picture.
I suspected capacitors with changed values in the vertical deflection circuit and the horizontal deflection or pin correction circuits. Since the TV is already in the vicinity of being ten years of age, I also considered the possibility of dry solder joints.
Since there was no obvious bulging capacitors in my initial inspection of the main PCB I proceeded to resolder the deflection circuits and some parts of the chopper transformer, filter capacitors and rectifier diodes in the secondary circuit of the power supply.
After the soldering exercise, I powered-up the TV again to check if the problem was solved. I was not much surprised to see that the problem still persists since there was not really any obvious cracked or dried up solder joints on the TV's circuit board.
Doing another visual inspection on the component side of the PCB, I noticed the slight bulge on the top of a filter capacitor that was sitting beside the chopper transformer. I desoldered the capacitor and found out that it is a 100uF/160V electrolytic capacitor on PCB location number C609. A look under the capacitor revealed signs of electrolyte leakage. With the capacitor leads still hot from contact with the soldering iron I can still see the electrolyte boiling out of one of the capacitor leads.
By replacing this capacitor only, I was able to solved both the problem with reduced horizontal width and vertical mislinearity.
During my initial observation of the problem I also noticed that the vertical size of the picture is in overscan - or stretched - resulting to vertical mislinearity and the presence of red, blue and green blanking lines at the top edge of the picture.
I suspected capacitors with changed values in the vertical deflection circuit and the horizontal deflection or pin correction circuits. Since the TV is already in the vicinity of being ten years of age, I also considered the possibility of dry solder joints.
Since there was no obvious bulging capacitors in my initial inspection of the main PCB I proceeded to resolder the deflection circuits and some parts of the chopper transformer, filter capacitors and rectifier diodes in the secondary circuit of the power supply.
After the soldering exercise, I powered-up the TV again to check if the problem was solved. I was not much surprised to see that the problem still persists since there was not really any obvious cracked or dried up solder joints on the TV's circuit board.
Doing another visual inspection on the component side of the PCB, I noticed the slight bulge on the top of a filter capacitor that was sitting beside the chopper transformer. I desoldered the capacitor and found out that it is a 100uF/160V electrolytic capacitor on PCB location number C609. A look under the capacitor revealed signs of electrolyte leakage. With the capacitor leads still hot from contact with the soldering iron I can still see the electrolyte boiling out of one of the capacitor leads.
By replacing this capacitor only, I was able to solved both the problem with reduced horizontal width and vertical mislinearity.
Saturday, March 14, 2009
Sony TV KV-1982NG Power Supply Problem
Symptom: Dead set
Cure: Replace R602(220K ohm/0.5W)
Repair details:
No voltages measured at collector terminal of horizontal output transistor.
Voltage supply was measured across power supply filter capacitor terminals. Traced the PCB foil from the B+ terminal of the positive side of power supply filter capacitor to 220K ohm resistor(R602). B+ is measured on one side of the resistor R602 but no voltage measured on its other terminal. By using ohmmeter test it is found out that R602 is open-circuited.
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Cure: Replace R602(220K ohm/0.5W)
Repair details:
No voltages measured at collector terminal of horizontal output transistor.
Voltage supply was measured across power supply filter capacitor terminals. Traced the PCB foil from the B+ terminal of the positive side of power supply filter capacitor to 220K ohm resistor(R602). B+ is measured on one side of the resistor R602 but no voltage measured on its other terminal. By using ohmmeter test it is found out that R602 is open-circuited.
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