lcd tv power supply problem

[jerrylmc]

Hello,
I have a power supply from a Haier tv that i am having problems with what to check next. The supply is a AD301M24-4N1. The supply turns on but with it connected to the mainboard the outputs are low. The 12v shows 6v, the16v shows 9v and the 24v shows 15v. i disconnected the supply completely and jumpered the ps/on pin to the 5v standby and all the voltages come up to spec.
If I connect a load to any of the outputs the voltages all drop back to the lower readings. Could some please advise me on this!
Thank You for your time!
Jerry

[budm]

Re: lcd tv power supply problem

1) We need good clear pictures to see what we are dealing with.
2) If you have everything connected, what is the PS-ON Voltage when you hit the TV's power switch to turn the TV on.

[jerrylmc]

Re: lcd tv power supply problem

Hello budm,
I have 4.9 v ps-on voltage. I'm having a problem with my camera so I will get back to you as soon as I can.
Thank you

[jerrylmc]

Re: lcd tv power supply problem

Here is a picture of the power supply.

[R_J]

Re: lcd tv power supply problem

I would start by replacing these 4 caps, they like to dry out and go open.

[jerrylmc]

Re: lcd tv power supply problem

Do you mean the four caps on the 24v rail? What would cause the voltage to drop across all the dc outputs except the 5v standby?

[nomoresonys]

Re: lcd tv power supply problem

Look closely, they are circled in red.

[jerrylmc]

Re: lcd tv power supply problem

Thank you, I will replace those caps and post back.

[jerrylmc]

Re: lcd tv power supply problem

Hello,
I have replaced the four caps shown with new caps. The problem in my first post still exists.
Thank you
Jerry

[R_J]

Re: lcd tv power supply problem

What is the voltage across the main capacitor (150µf/450v) If the output voltages are there without load the power supply is working, if they drop when loaded it can be bad feedback to the primary.
Some people have found the output caps to be bad also 1000µf/16v and 100µf/25v

[jerrylmc]

Re: lcd tv power supply problem

The voltage across the main cap is 167v dc. When supply is powered on that voltage drops to 150v dc. I have already replaced the other caps.

Jerry

[nomoresonys]

Re: lcd tv power supply problem

Should be around 400 when powered on.

[nomoresonys]

Re: lcd tv power supply problem

Check all the diodes, sometimes it's a rectifier diode gone bad.

[R_J]

Re: lcd tv power supply problem

That voltage on the main cap should not drop to 150v but should go to around 400v when turned on, The pfc circuit is not working.
It is either defective or is not being turned on via the optocoupler.
I checked a couple other threads and it should have around 400v on the main cap when turned on.

I would need clear pictures on the bottom of the board.

[budm]

Re: lcd tv power supply problem

1) Will the PFC boosted Voltage stay on if Inverter board is not connected?
2) We need pictures that show all the boards and how they are connected together.