Sony KDL42EX440 no red light

[geminidpr]

Customer says red light was coming on but when I plugged it in I got no red light. I'm getting the standby 3.3 volts and I'm also getting a Power on/off voltage of 3.3 volts but when I press the power button that voltage doesn't change. When I remove the cable going to the main board I still have my standby at 3.3 volts but the Power on/off voltage drops to 0 volts so I guess the main board is OK. Any help would be greatly appreciated. Thanx.

[budm]

Re: Sony KDL42EX440 no red light

" I'm also getting a Power on/off voltage of 3.3 volts but when I press the power button that voltage doesn't change" That means the main board is not working, it should toggle HI and LO when power switch is activated on and off.
What DC voltage do you get at the main filter cap of the power supply board? You need to measure it right at the two legs of the cap.

[geminidpr]

Re: Sony KDL42EX440 no red light

I'm getting 160 volts so I guess something is wrong cause the cap is rated at 450V.

[budm]

Re: Sony KDL42EX440 no red light

If you have PS_ON, then that should turn on the PFC Voltage booster circuit on the power supply board which voltage on the cap should rise up to 360~400VDC range.
Can we see the pictures of the boards and also the labels on the connectors to verify some voltages.

[geminidpr]

Re: Sony KDL42EX440 no red light

This is the best I can do right now. The panel voltage isn't indicated but the audio voltage should be 12 Volts and the VCC is also 12 volts and they all read 0 volts so I guess the power on/off voltage of 3.3 volts isn't firing those circuits.

I will try to take some better photos tomorrow. Thanx budm.

[geminidpr]

Re: Sony KDL42EX440 no red light

If there is a specific area u need a close-up of, just let me know.

[geminidpr]

Re: Sony KDL42EX440 no red light

Please remove my previous two posts with pictures. I read your post on how to add pictures and the images look better.Thanx.

Budm...I checked your link to photobucket and saw photos of this TV in your album so if you want we can use your links instead.

This is the link to your photos of this TV: http://s807.photobucket.com/user/bud...?sort=3&page=1



https://www.badcaps.net/forum/attach...1&d=1402096152

https://www.badcaps.net/forum/attach...1&d=1402096681

[geminidpr]

Re: Sony KDL42EX440 no red light

According to this flo-chart the problem is in the power supply but the service manual does not give you the schematic so I guess I'll have to order a new power supply. Thanx for your help.

https://www.badcaps.net/forum/attach...1&d=1402175870

[holmzy]

Re: Sony KDL42EX440 no red light

I had similar issues with a sony ex tv. I checked everything!! last thing that was left was the sony chip at the back of the board and surrounding components. turns out a diode connected to the sony chip that controls most power functions on the board had shorted. SMD so could not tell what the diode was. tried a random smd diode and green light came on but no power. then anther random smd diode (both similar size) the set booted!

[geminidpr]

Re: Sony KDL42EX440 no red light

Thanx holmzy. I'll check that out on mine and will post the results.

[geminidpr]

Re: Sony KDL42EX440 no red light

Thanx holmzy for making me take a second look at it. All the diodes were fine but I decided to replace the 110 uf 450V main filter capacitor C6530 and it fired right up. It wasn't bulging but it would charge up to 400V when I plug it in and then slowly go down to 160V and then stay there. My thanx to budm also who asked me to check the voltage there.

[holmzy]

Re: Sony KDL42EX440 no red light

well done!

[jamie_ydr]

Re: Sony KDL42EX440 no red light

I have the same problem. The set was hooked through power strip and TiVo also. Now both have no power. I went direct to outlet no power and no lights. No 3.3 voltage. No lights or clicking at all any suggestions. I saw the flow chart. Power supply but another tech tells me main board supply lies the voltage to power supply. Confused. How do I check the 450 volt cap. In or out of of circuit. I have a digital mm buy don't know which is capacitance. I want to buy possible supply and be wrong. Can some one help me. I do board replacement and am trying to get into component level. I can solder. I worked rework at compaq computer for 10 years. No oscilloscope either. What will I need to perform actions your are suggesting. And do you have divinely part number for 110Uf 450 volt cap? Email me at jamie_ ydr with reply it's quicker for me to diagnose. Thanks in advance Jamie

[dudleyfj40]

Re: Sony KDL42EX440 no red light

Old thread revival.

Jamie, You should have 400 vDC across the cap leads.

I have the 400 VDC and the 3.3 standby voltage, but no 12v.

I have been searching for a power supply board to purchase with no luck.

Has anyone found a schematic for this?