IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

[max1636]

I'm working on a Sony KDL-46W5500, power board part no. 1-878-599-11, discovered something strange while probing around. I read 245v AC going into the bridge rectifier but 330v DC Coming out?

Is this normal? I've never metered a mostly working board before so I don't know. I presume 330v DC is there because that's what the main cap is charged to?

[budm]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

That is a little low actually, the cap will charge up to the peak of the AC sine wave minus the voltage drop of the rectifier diodes.
So 245Vac x 1.414 = 346VDC. Then you also have PFC voltage booster that will boost up to around 380~400VDC when TV is turn on.

[max1636]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

That is a little low actually, the cap will charge up to the peak of the AC sine wave minus the voltage drop of the rectifier diodes.
So 245Vac x 1.414 = 346VDC. Then you also have PFC voltage booster that will boost up to around 380~400VDC when TV is turn on.

The problem with this set is that it powers on for some time with nothing on screen and no backlight, then turns itself off, blinks 13 times once, then blinks 14 times and repeats.

All voltages on the connector to the control board (AV Input) are correct and standby voltage is correct. However there is no voltage going to the inverter board at any time. Are those big transformer that go to the inverter board known to go bad?

[budm]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

That is the high voltage transformer, its output feeds the Balancer board which are then fed to the lamps. I doubt that it is the transformer.
You should download the service manual to look up the error code for this chassis model.
http://elektrotanya.com/?q=showresul...oria=&kat2=all

[max1636]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

That is the high voltage transformer, its output feeds the Balancer board which are then fed to the lamps. I doubt that it is the transformer.
You should download the service manual to look up the error code for this chassis model.
http://elektrotanya.com/?q=showresul...oria=&kat2=all

Thanks heaps for that I'd been looking for a service manual that there alone probably just saved me another $60 I would of wasted on buying a new power board. 14 Flashes indicates a bad T-Con board, I've never had a bad T-con before. Could it be that fuse that I always here about on T-con boards that blow?

[budm]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

Yes, check the fuse with Ohm meter first, then check for DC voltage (TV turn on) at both ends of the fuse with the meter black lead on the chassis for Ground ref.

[max1636]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

Yes, check the fuse with Ohm meter first, then check for DC voltage (TV turn on) at both ends of the fuse with the meter black lead on the chassis for Ground ref.

I can't believe it! The fuse is actually blown. I took the board out the other day to look for it but I couldn't find it but I was looking in the wrong place. I see a very small 7A Beside the logo would it be unsafe to bridge the gap temporarily with a piece of soldier of some kind of very thin wire?

[budm]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

7A, that will be really high current for T-CON. Can I see the picture? Never seen fuse that size used on T-CON.

[max1636]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

7A, that will be really high current for T-CON. Can I see the picture? Never seen fuse that size used on T-CON.

I also just definitely confirmed that it's blown, I'm getting 12v on one side, and not on the other.

[budm]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

OK, use the Ohm meter black on the chassis, red on the fuse's end to see if it shows low Ohm reading, we need to find out if the fuse just failed or the circuit has shorted out and caused the fuse to blow.

[max1636]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

OK, use the Ohm meter black on the chassis, red on the fuse's end to see if it shows low Ohm reading, we need to find out if the fuse just failed or the circuit has shorted out and caused the fuse to blow.

It's difficult to measure since it's all over the place, on the side where the F1 is after having it on there for some time I get about 2 M Ohms, but it kept slowly going down, on the other side I get about 2 K Ohms, but it was slowly going up.

[budm]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

That is fine, as long as it does not show something less than 100 Ohms.
Here is the training manual for your chassis.

[max1636]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

That is fine, as long as it does not show something less than 100 Ohms.
Here is the training manual for your chassis.

Thanks! I really appreciate the help. So does that mean there is no short on the T-con and the fuse may of just blown?

My local electronics shop don't sell Surface Mount fuses I would probably have to get one online or just get a whole new board but just temporarily would it be a bad idea just to have a small piece of soldier across the fuse?

[budm]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

I use PICO II fuse with two legs, you can use 7A car fuse and any fuse you may have and solder the wire to the two end of the fuse or scrape off the Green coating on the board for you to solder the wire to. I will not try jumper just in case there is shorts further down the circuits that get switched on so the short will not show up when we do the inactive Ohm testing.

[max1636]

Re: IS THIS NORMAL?? 330V DC From Bridge Rec. Only 245v AC Going In!?

I used a 7A Car Fuse but I get the same 14 Flashes. I The board must be bad then I guess so I'll buy a new one. Thankyou again for your help though I was going to buy a power board today so at least I'm buying the right one now.