haier le42b1380 power supply issue

[budm]

Re: haier le42b1380 power supply issue

Yes, it should read open circuit against the chassis, if it shows resistance then the wire may be nicked and shorted to the chassis, so yours are not.
To find the individual LED that has open circuit will be quite a bit work since the screen will have to be taken apart to get to the string.
I made this indicator to find out which string has open circuit.
https://www.badcaps.net/forum/showpo...&postcount=107

[freakaftr8]

Re: haier le42b1380 power supply issue

Thats cool!. on this power supply I have absolutely nothing coming out of the secondary side of the transformer. It's almost as if the whole second side where the 12 and 24 volt supplies are Dead. Nothing on any of the capacitors it's absolutely dead the only thing I have is 5V standby andwhen I power the set up at 5v that's it.

Even tried shorting across the opto isolator for the 12 volt supply and I still get nothing maybe that's not the right way to do things but I got nothing. I've pretty much tested every single SMD resistor diode zener diode capacitor that I could find it I at least see nothing wrong with this board I have to be overlooking something

[freakaftr8]

Re: haier le42b1380 power supply issue

That's takes the pain out of pulling the panel! Remember when last year I dissected an 80 inch sharp panel to find a bad led? That ones still on my wall working great. I've also done various 60 inch 46 inch and 42 inch panels as well. Not fun.

[freakaftr8]

Re: haier le42b1380 power supply issue

So I have voltage coming into the transformer buy nothing coming out. Isn't there a regulator that turns on the secondary side of the power supply? I'm trying to figure out and pinpoint the traces to what controls the ps-on. I'm getti g ps-on btw. Voltage on that pin goes from 0 to 3.84 so that s not an issue. Just the circuits that control 12 and 24 volt are dead I even probed the positive side of the capacitors on this area of the power board and nothing there although like I said as soon as I power up tthe tv green light comes on I get 384 volt at the primary capacitors but when I power off the 384 volts goes down to something nominal like 60.

[budm]

Re: haier le42b1380 power supply issue

Since the PFC Voltage booster is working so we know that the PS_ON is tuning on the switched transistor to supply the VCC to run the PFC IC (8-pin SMD IC) this VCC should also be supplying to the VCC pin of that 12V/24V SMD IC with 18/20-pin IC, so you need to look up the spec sheet of that IC to locate the VCC pin and see if it has voltage for it to run.

[freakaftr8]

Re: haier le42b1380 power supply issue

You mean the PFC ic on the primary side? Well that's like -56v dc.
Not too sure how to read voltages on the primary side...

[budm]

Re: haier le42b1380 power supply issue

"YesI'm getting 384v at the filters." per post 7, you are getting the boosted voltage as measured at the two legs of the cap.
When you make voltage measurement in the primary side, the negative leg of the filter cap is the Gnd ref point for the meter.
When measure the voltage on the secondary side, the chassis can be used for the gnd ref for the meter.
Did you get the P/N of that second IC so we can find the VCC pin?

[freakaftr8]

Re: haier le42b1380 power supply issue

Ok so i decided to start tapping around the board for bad connections and tapped the primary side of the main transformer and briefly got 12v. So it's a bad connection or a faulty transformer possibly. .

[freakaftr8]

Re: haier le42b1380 power supply issue

Learn something new every day. Never knew that the ground reference for the primary side was the negative leg of the main filter capacitor. Lol thanks

[budm]

Re: haier le42b1380 power supply issue

You may want to check the works you have done on the board then, looks real well at all the connection and traces to make sure there is not cracked traces and poor solder joints.

[freakaftr8]

Re: haier le42b1380 power supply issue

ok found it. Bad solder connections on the main transformer. Resoldred and now when I power it up or plug it in I get a brief flash of the LED lights it appears the lower left hand corner is dark then it shuts down if I press the power button the green light comes on but nothing when I first power it up I can watch the 12 volts briefly rise and then drop to 0 so this maybe now and LED backlighting problem

[freakaftr8]

Re: haier le42b1380 power supply issue

so now I'm looking at some dead LED strings. this power supply obviously goes into protect mode immediately after following up that one of the four connectors are not being fed the same driven by the LED driver but this power supply is a rudimentary version and does not offer A diagnostic code so the power LED just stays lit green instead. I wonder if this is the initial problem that blew the MOSFET transistors to begin with

[budm]

Re: haier le42b1380 power supply issue

"I get a brief flash of the LED lights it appears the lower left hand corner is dark then it shuts down if I press the power button the green light comes on but nothing when I first power it up I can watch the 12 volts briefly rise and then drop to 0 so this maybe now and LED backlighting problem" That is the same problem after 1/2 Hours, I had i let it cooldown for about 1/2 Hour before I can turn it on again. I did not tryswapping the LED string connectors to see if the problem will move from the bottom left corner or not.

[johnboy1313]

Re: haier le42b1380 power supply issue

Yes, it should read open circuit against the chassis, if it shows resistance then the wire may be nicked and shorted to the chassis, so yours are not.
To find the individual LED that has open circuit will be quite a bit work since the screen will have to be taken apart to get to the string.
I made this indicator to find out which string has open circuit.
https://www.badcaps.net/forum/showpo...&postcount=107

Bud, can you elaborate a lite on your string tester? Is this something you place in series with each LED string? What is the indication of a good string? What about a bad string? I have a 50" Element LED that I thought had a bad PSU. I bought one with a cracked screen and swapped the PSUs. The suspected bad PSU worked in the cracked screen TV. The known good one didn't work in the TV with the good screen. I'm suspecting an LED string, but I'd like to test if possible before ripping into it.

[freakaftr8]

Re: haier le42b1380 power supply issue

well I swapped the LED connectors all over the place and still get a dark lower left hand side of the screen. However I should know that I did replace a Schottky barrier diode with a higher wattage rating. Not sure if this has anything to do or not with load leveling or something to that nature but there's two diodes up by the output connectors one was fried so I replaced it with one I only could find. I am getting roughly 35 volts to All 4 connectors

[budm]

Re: haier le42b1380 power supply issue

I will not be surprise at all if it is bad LED strip, they do not do a good job at dissipating the heat away from LED, so far the most common failure I see on these LED TV are due to failed LED, see so many threads here. i.e.: https://www.badcaps.net/forum/showth...324#post503324
It does not seems to matter what brands you buy.

[freakaftr8]

Re: haier le42b1380 power supply issue

Yep. In a few of the sharp TVs most notably the notorious lc-60le810un model that so many people on here have issues with I just ended up bridging the one bad led by the connector. Gave the set.to a family member that uses it every day and never turns it off. Still working great and you cannot notice one led out.

I have repared about 5 LED TVs with bad LED strips or one bad led on the strip so I know what I'm in for

[budm]

Re: haier le42b1380 power supply issue

I sure like to find good sources for these replacement LEDs.

[freakaftr8]

Re: haier le42b1380 power supply issue

The only one I know of and I have used a few times is ccflwarehouse.com

[johnboy1313]

Re: haier le42b1380 power supply issue

Guys, I may have made a discovery that pertains to your issues. I may not have. As I said previously, I'm working on an Element ELEFT502 with a very similar setup. I have one with a good screen but no backlight and one with a cracked screen but good backlights. I swapped the PSUs and nothing changed. The cracked screen still had backlights. Long story short, with the T-Con unplugged from the mainboard, the backlights on the good screen would flash briefly. I have the screen off so I could verify that all LEDs lit. I connected the t-con, even though there is no screen connected to it, and the panel lit and stayed lit. The set with what I suspect is a bad LED doesn't flash at all. Check the backside of your main board and see if there's a pin labeled in such a way to suggest that it signals the lights to light. In my case the pin is called "ON-PANEL". There is an EEPROM available for the SE421TT. If all your LED strings check good, maybe the EEPROM is the solution.