power board faulty BN44-00197A

[ebenedekfi]

Working on a Samsung LE40A430T1,with a power board faulty BN44-00197A.
In first stage I changed following caps: CM804, CM806, CM809, CM812, CM810, CM808
Resistor RM851, RM852, RM853 are burnt, i changed it, and I changed the IC ICM802 too.

Now my problem:

Standby voltage 5.3V is OK, if the mainbord is not plugged in, but if plugged in MB the standby voltage become 2.1V-2.3V instable. without MB ribbon plugged in, the power supply starting ok, 13V ok, 12V on inverter ok.
Please help.

Endre

[Andrew F. Ali]

Re: power board faulty BN44-00197A

OK. So you determined the PSU is working now. but did you see the backlights come on?....However, you do have a Main Bd. problem.

[ebenedekfi]

OK. So you determined the PSU is working now. but did you see the backlights come on?....However, you do have a Main Bd. problem.

Thank for your reply.
No backlight, nothing. Before I replaced the caps, red standby light blinked. Now nothing.

[Andrew F. Ali]

Re: power board faulty BN44-00197A

You said you have 12V to the Inverter. Were the backlights plugged in? If yes, then you may have an inverter issue or backlight issue as well. BTW how did you get the PSU to come on without the Main Bd. connected?

[ebenedekfi]

Re: power board faulty BN44-00197A

I put a jumper pin1-pin3 on connector CN801.
Pin1- power on-off
Pin3- stb 5.3V

Pin1 at conn. CNI803 (inverter on/off) I measured 0V.

[ebenedekfi]

Re: power board faulty BN44-00197A

I measured 12V on pin1 conn CNI806

[ebenedekfi]

Re: power board faulty BN44-00197A

If I shorting inverter on/off and stb 5.3V , the backlight come on.

[Andrew F. Ali]

Re: power board faulty BN44-00197A

That means you PSU is good and your Backlight drivers are OK, too. You have a Main Bd. problem, as I stated in Post# 2.