Samsung LCD Power Board turning on and off.

[waitery]

Re: Samsung LCD Power Board turning on and off.

OK, read his post and here is what I get from Pin #1:

.35 volts, then I hit the power button and we're at 3.7 volts. I kept hitting the power button, the voltage hits 3.7, then goes back down to .35. It's there, it's just not starting it up.

[retiredcaps]

Re: Samsung LCD Power Board turning on and off.

Green ones are Lelon and the other smaller brown ones are Samwha. To your point, there are a few that the tech didn't swap out and they are KMG brand.

Members will probably chime in and recommend that you replace all the above with Panasonic FM. One or more of those caps could have high ESR which explains why the tv is flakey in turning on. As the set warms up, the cap ESR drops.

[retiredcaps]

Re: Samsung LCD Power Board turning on and off.

OK, pin 3 reads good at 5.10 and it is steady...we are good there.

How should I proceed?

On pin 1 (PS), re-read post #4 and what PlainBill says. So measure pin1. If you have min/max on your dmm, this is a good time to use it.

[waitery]

Re: Samsung LCD Power Board turning on and off.

OK, pin 3 reads good at 5.10 and it is steady...we are good there. Here are the brands that I am seeing:

Green ones are Lelon and the other smaller brown ones are Samwha. To your point, there are a few that the tech didn't swap out and they are KMG brand.

How should I proceed?

[retiredcaps]

Re: Samsung LCD Power Board turning on and off.

Pin 3 is your standby. It needs to be 5V DC before the TV will turn on. If it is 0.007, then like your lcd, either the startup cap is bad, the smps controller, or something in the circuitry.

I see a variety of vents on the caps which tells me that Samsung cheaped out and didn't replace all the caps with Panasonic. That green color is still unknown and I see UCC (brown). Please list all the caps manufacturers and brands. UCC KZG are bad caps and they fail without bloating. You see KZG in a few motherboards.

[waitery]

Re: Samsung LCD Power Board turning on and off.

Sorry, I thought that you might go there.....I should have just typed it out. Here is the way that the rail is comprised:

Two lines of pins running side by side, 12 in each line, so 24 total. The lines are listed as follows:

1-2 PS NC
3-4 SB GND
5-6 GND GND
7-8 12.8V 12.8V
9-10 GND GND
11-12 GND GND
13-14 5.3V 5.3V
15-16 5.3V 5.3V
17-18 GND GND
19-20 12V-GND
21-22 12V 12V
23-24 NC NC

Above that rail is another smaller rail, single line of 5 pins as follows:
1 BLU
2 ADIM
3 PWM
4 GND
5 +5V

I am showing .007 volts on all +5 and +5.3 lines, assumes everything is connected to the main board, power on and hitting the power button.

[retiredcaps]

Re: Samsung LCD Power Board turning on and off.

This is the 24 volt rail.

I did an edit in post #2. Please also do the same for the top connector. We need to find where 5V SB is first. Then PS_ON.

[waitery]

Re: Samsung LCD Power Board turning on and off.

This is the 24 volt rail. 14 pins in total, pins running top to bottom in this order:

NC
BL
GRD
GRD
GRD
GRD
GRD
24V
24V
24V
24V
24V

I got .72 vdc coming out of these....it is connected to the main board and I am trying to fire up the LCD with the power button.

[retiredcaps]

Re: Samsung LCD Power Board turning on and off.

And PlainBill discusses in general how TVs work with the 5V SB and main board at (just 30 minutes ago)

https://www.badcaps.net/forum/showpo...6&postcount=17

[retiredcaps]

Re: Samsung LCD Power Board turning on and off.

1) If they replaced the caps, check the soldering work for cold joints with a 10x magnifying glass. Maybe the tech who did it isn't all that great at soldering?

2) What are those light green caps? Who makes them and what series are they?

[retiredcaps]

Re: Samsung LCD Power Board turning on and off.

can someone give me some insight as to where I can run through critical voltage points and troubleshoot this board?

On the bottom right is connector. List each connector, its legend, and DC voltage.

Maybe one says 5V SB?

edit: There is also a connector at the top. Do the same.

[waitery]

I have a Samsung LCD that has a Dong Yang MK32P5B series Q power board that is having issues. Sometimes the TV comes on, sometimes not....very sporatic. Main filter cap looks good at 172.2 VDC, but nothing on the rail. Samsung recapped this with Panasonic EB's and FM's for free under their capacitor program, but it was having problems before that (which is why I had them do the recap). I thought that this might have solved my problem, but it has not. I have posted pics below....can someone give me some insight as to where I can run through critical voltage points and troubleshoot this board? Thanks in advance!!