Samsung PN43F4500FXZA turns on no picture or sound

[nwelec]

TV turns on I get proper VA of 58V but VS is 250V and should be 208V and I can not adjust it with the pot. Also voltages at CN4009 are correct when first turned on then they start to drop to 0. I can not find any thing online about this problem with this model and was hoping for some direction.

[Beau28713]

Re: Samsung PN43F4500FXZA turns on no picture or sound

Remove pot and test pot for proper operation first. Then move on.

[R_J]

Re: Samsung PN43F4500FXZA turns on no picture or sound

What meter are you using to measure the Vs voltage, sometimes cheap meters react that way due to the high y drive pulses (lg/goldstar meters act that way)
This may not be your problem but I thought I would mention it.

You say the voltages on CN4009 are correct? pin 6 is the Vs pin, so it is 208v? then drops to 0

[nwcs]

Re: Samsung PN43F4500FXZA turns on no picture or sound

I use a Fluke 77 and have used fluke for 40 years. I will check the pot in the morning to see if it is defective. I will check pin 6 again tomorrow to see what it reads.

[R_J]

Re: Samsung PN43F4500FXZA turns on no picture or sound

I only mentioned the meter because I (and a couple others) have seen this, I normally use a Fluke but also have a cheap lg on the bench and on some plasma's, checking the Vs, even on 1000 volt scale will show OL. So I check with the Fluke and the reading is fine.

[nwelec]

Re: Samsung PN43F4500FXZA turns on no picture or sound

So I tested both the pot which does adjust out of circuit and pin 6 of CN4009 which I thought was dropping but I found that it is steady at 250v but all other pins drop to 0v.

[R_J]

Re: Samsung PN43F4500FXZA turns on no picture or sound

That high voltage could be due to a lack of feedback to control the voltage, check the components around the control all the way to the optocoupler, I would also check on the primary side of the optocoupler. most power supplies go down in voltage when they loose feedback for safety
Check that 0Ω off of DS853C, It supplies the low voltage for the feedback circuit on the secondary

[nwelec]

Re: Samsung PN43F4500FXZA turns on no picture or sound

Don't know how I missed this but there is corrosion all over the power supply board.