Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inverter)

[SmartSped]

Hello,

I have a Samsung 320MP-3 (LH32HBPLBC/ZA) that the power keeps cycling on and off on. When I plug it in, the light turns green and what seems to be a perfect picture displays. After about 3 seconds, it shuts off and the standby light blinks about 3 times and then tries to turn back on again, repeating the process. I have already replaced the caps on the inverter board and power board and saw absolutely no change in the TV's functionality. Does anyone know what else could be wrong with this TV?

EDIT: I will upload photos when I can get the forum to stop logging me out every time I try.

[SmartSped]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

Ok finally. Here's some pics of the LCD.

[CapLeaker]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

What does PSon and BLon do on the power supply when the TV is cycling all the time?

[SmartSped]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

Hey thanks for the response. I ran tests on the the PS-on and BL-on pins. The PS-On pin gets 2 volts through the whole process after I push the power button. The Bl-On gets 3.3 only when the backlight cycles on/off. One thing strange I noticed while doing this test was a low hissing/crackling noise coming from the bottom of the inverter board around the bottom transformer. Sounds kind of like a cat hissing. After the backlight cycles on, about a second later, the hiss slowly developed and then stops when the backlight shuts off. Could there be something wrong with that bottom transformer and are there any tests I could run on it to be sure?

[budm]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

Unhook the cable from the power supply board to the inverter board and see if the TV will still cycling on and off, sounds like you have high voltage arcing or frying transformer.

[SmartSped]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

Yes it still cycles on/off. Ps-on and Bl-on maintain the same operation as before. Would it be possible that it may still do this because now it can't find the board?

[budm]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

So let me get this straight, without the inverter board connected, PS-ON is still showing steady 2V but the power supply and TV indicator light are cycling ON and OFF?
the 24VDC output feeding the inverter board is also going up and down too?
If PS-ON is steady and no inverter board connected but the power supply outputs are going up and down then you have problem in the power supply section.
BTW, the two legs of the big brown main filter cap laying on its side looks like it has some kind of brown corrosion on them?
Some one try to fix this board or other boards before? because the cap is bigger (longer) than the original one compared to the one from shopjimmy, other caps also look like they were replaced.
What is the history on this unit?
Please also upload the pictures of the bottom side of the power supply board.
Power supply board: Samsung BN44-00416A
http://www.shopjimmy.com/samsung-bn4...upply-unit.htm
Picture provided by shopjimmy.

[SmartSped]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

As I mentioned in the first post, I replaced ALL caps. All of them are correctly installed and have proper values. Some have higher voltage requirements but that's it. Before I replaced all the caps the TV was doing the exact same thing.

So just to be clear on the situation, without the inverter board installed:

PS-on and BL-on (from main board to power board) give me constant 2v and on/off cycling 3.3v respectively. I measured the 24v lines from the power board to the inverter board and all 5 have steady 24v. I also checked the BLU-on/off line going from the power board to the inverter board and it was doing the same cycling on/off thing at 3.3v.

I will upload a pic of the bottom of the board in a little bit.

[budm]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

OK, thanks for the clarification, I just do like the stain on the main cap legs which does not look normal to me. Reading post 4 with reading of 3.3V and we thought it is steady but the inverter was going on and off, but that is not the case.
So the power is fine since the 24V is steady that is what throw me off. It is the backlights inverter being turning on and off.
The BL-ON is generating by the main board so we need to do now is to find why the BL-ON is cycling.
Looking at the inverter board, the transformer next to the connector from the power supply, there a chart printed just below the transformer to tell you what each pin of the inverter connector is for, we need to see if there is any feedback pin to feed the main board to tell the condition of the inverter board or not (most of them do not use the error feed back signal).
What you can also do is to disconnect just the BL-ON wire ON THE POWER SUPLY SIDE that goes to the inverter board and then use 1K resistor between that BL-ON wire and the STBY 5V to simulate staedy BL-ON signal and see if the inverter will stay on or not.

[SmartSped]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

I see what brown spots you're talking about now. That's where I got messy from the flux and the light isn't shining on it. It looks a lot clearer than what it is in the pic. I'll do some more testing per your instructions and report back tomorrow.

[budm]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

So if we are able to force the backlights to come on and stay on using the resistor then we know that is the main board problem with the BL-ON control line, but what is bugging me is that in post 5 I asked you to disconnect the inverter board and you indicated that the TV is STILL cycling which does not make sense since you are getting steady 24V so I do not really know what was cycling in that mode sine the PS-ON is steady.

[SmartSped]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

I'll be at work for most of the day but until then, I did take a couple of more photos including the bottom of the power board and pinout for the Inverter cable.

How would I tell if the error pin is being used or not by the inverter?

And yes, it does seem weird that everything seems normal except BL-on cycling on and off.

[budm]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

You need to trace out pin 11 of CNI801 on the power supply board to see if it is routed to the connector that goes to the main board or not.

[SmartSped]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

I traced that error pin all the way to the main board where it leads into a couple of resistors right next to the plug. On the main board side of the power board, the pin is labeled DET_5v

Should I go ahead and try to force BL-on with a 1k resistor?

[budm]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

So if you check the resistance between the Inverter error pin and the DET_5V pin, it will show 0 Ohms?
Go ahead and do the force on, but you MUST disconnect that BL-ON wire going back to the main board first otherwise the main board will still be able to control the BL-ON line.

[SmartSped]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

I checked the Ohms all the way from the inverter board to the DET_5v and I got very close to 0 Ohms. I even wiggled the cable around a little to make sure there wasn't a open circuit somewhere. I thought I had 1K resistor but it's one of the ones I don't have. I'm gonna order one and as soon as I get it in to test it, I'll report my findings. I have the BL-on wire pulled from the plug.

[SmartSped]

Re: Samsung 320MP-3 Power cycles on and off (already replaced caps on power and inver

Put the 1K resistor on the A5V and BL-On pins and turned on the TV. It will still shut off (backlight included) after about 3 seconds. The only difference being that when it tries to turn on again, the green light turns on for a couple of seconds less and nothing shows up on the screen and then repeats this process.