Hi,

I got this samsung tv power supply board. upto bridge rectifier i am getting good AC voltage 120V and good DC voltage 160v. But at the main capacitor i am getting 390v which is too much. BN44-00498B is the board number.

 

Hi,

I got this samsung tv power supply board. upto bridge rectifier i am getting good AC voltage 120V and good DC voltage 160v. But at the main capacitor i am getting 390v which is too much. BN44-00498B is the board number.

Have you looked for the service manual and schematic?

 

Have you looked for the service manual and schematic?

i did not get same but i got similar schematic.

 

And which capacitor are you seeing at 390V? I see several on the schematic rated for 450V. That must be for a reason.

 

Does the TV work with either 120V or 240V with a switch or link to select which?
If so then it may use a voltage doubler when set to 120V to keep the voltage the same for the rest of the circuit.

 

This board is to work with only 120v. i am getting PS_On voltage even thought it is not given.

 

And which capacitor are you seeing at 390V? I see several on the schematic rated for 450V. That must be for a reason.

CP814S. in my board it is CP806 rated 450v.

 

CP814S. in my board it is CP806 rated 450v.

That cap should be seeing the same voltage across it as the bridge shows, less the diode drops and the voltage across the low-ohms shunt resistor. I'd take a look at that shunt resistor and see if it may have failed open.

 

That cap should be seeing the same voltage across it as the bridge shows, less the diode drops and the voltage across the low-ohms shunt resistor. I'd take a look at that shunt resistor and see if it may have failed open.

that resistor is good.

 

That cap should be seeing the same voltage across it as the bridge shows, less the diode drops and the voltage across the low-ohms shunt resistor. I'd take a look at that shunt resistor and see if it may have failed open.

Can you please tell me what should be the resistor value for the attached resistors please. i am getting very low ohms almost like short.

 

0.1Ω and 0.36Ω so they would read very much the same as a short circuit.

 

That cap should be seeing the same voltage across it as the bridge shows...

I retract that statement. I was too hasty in reading the schematic.

Can you please tell me what should be the resistor value for the attached resistors please. i am getting very low ohms almost like short.

I would say they could be inductors but the "RS" label implies resistor or even shunt resistor. I'm thrown by the black band. Otherwise they would read as 20 x 0.01 = 0.2Ω and 36 x 0.01 = 0.36Ω, both at 5% tolerance. The black band might be brown? That would indicate a 100ppm temperature coefficient.

 

Take pictures of the power supply. Samsung Monitors had horrible Caps in the secondary of the PS. Look for bulging Caps.

kv

 

Can you please tell me what should be the resistor value for the attached resistors please. i am getting very low ohms almost like short.

RP820 on the circuit diagram is marked 1MF, which suggests 1 Meg ohm, as there are 4 in series, so you could compare it with the others,, but the colours suggest otherwise,...low value resistors like these are usually in series with the Mosfet Source pin or supply.

You need the correct diagram!!!