Quick Check For Sony Power Supplys
By Dan Mundy, CET/CSM

This is a fast check for Sony power supplies. The important thing to remember about these supplies is that it is a push pull amplifier. The load across the 2 transistors must be close to equal or it will self-destruct. The frequency is the regulating part of the equation. They are designed to start at a high frequency out of resonance and be pulled lower by the regulator toward resonant frequency to achieve proper regulation. The supply will oscillate at very low voltages and this is the only way to check them out.

After doing the usual repair of transistors and I generally include the damper diodes (you can use Sony parts but they are subbing to a 1N5401). If you don’t know why the supply blew up check the Horizontal output and look for rings around the driver transformer.

First pull the relay RY602. This will prevent the set from trying to power up during repair and testing.

Monitor the voltage at Q601 collector or R607 is just as good. Scope Q602 collector for waveform and DC voltage.

Lower the AC voltage to 20 volts DC. The supply should be oscillating and each transistor should be dropping 10 volts. If that looks good run the DC up to 40 Volts.

At about 80 volts DC the current drawn by the supply should peek and start to decline with further increase in voltage. You should also have a nice square wave of equal duty time with no peeks or ringing. Each transistor should be dropping 40 volts.

You may see a slight bounce in the supply frequency at this time. The standby is up enough to turn the micro on and the slow start circuit is trying to bring the run supplies up to full value. Of course this won’t happen with the relay still out.

On the latest supplies you must stop and return the set to normal operation as they do not like trying to run on reduced voltage above 40VAC. Older sets have no problem and I continue to increase the DC stopping at 150 volts and 200 volts. These are nice round numbers that are easy to work with. If everything is looking OK then run the supply on up to full value. You should have 16 volts on D619 reference to cold ground.

The supply is now running at full voltage. If you have fixed all problems on the secondary side you can reinstall the relay and tune for minimum smoke.

Common Failures In Sony Direct View TV's
By Dave Wreski, CET Eastern Stereo/Videologic

This is a list of the common failures in the Sony Direct View. Most failures are caused by Vertical or Horizontal problems.

Sony Switch Mode Power Supply Rebuild Parts:

AA-1 Chassis Sony Part #
Q601 2SC4834 8-729-019-51
Q602 2SC4834 8-729-019-51
VDR601 Varistor 1-807-288-11
VDR602 Varistor 1-810-053-11
VDR603 Varistor 1-810-053-11
R607 Fusible 0.1 ohm 1-202-933-61
R644 Fusible 6.8 ohm 1-212-853-61

AA-2 Chassis Sony Part #
Q601 2SC4834 8-729-019-51
Q602 2SC4834 8-729-019-51
R607 Fusible 0.1 ohm 1-202-933-61
VDR601 Varistor 1-810-974-11

The above parts should be replaced as a set. Always check HOT circuit before repairing power supply. Resolder horizontal drive transformer and do a good visual check in that area. Check Vertical output IC for shorts or signs of overheating.