Funai LF320FX4F Power Supply Issue?

[Sageman98]

Re: Funai LF320FX4F Power Supply Issue?

TIPS for CHECKING and REPLACING LED's in back lights.
The LED's can short, blow open or even partially short! I actually replace the individual LED's on the internal strips. I have fixed many TV's that would otherwise go to the landfill. I'm talking nice TV's barely out of warranty. Remember, if you have a blown LED the circuit is open and will not light at all but keep reading, I will explain..
When you think its a back light issue:
Smaller TV's like 32 inch sets have just one series circuit where all LED's are in series like holiday lights. One blows and they all go dark and stay dark. If your panel is flashing on for a second you are probably looking for 2 or more shorted LED's. When they short out and the current drain is too high making the protect circuit shut down the set. Larger sets have 2 series circuits where one may turn on for a second and the other does not because of an open LED somewhere in the series. The protect circuit will still shut down the good circuit when it senses the other circuit is an open circuit, causing the voltage to climb too high. Various problems to look for with back lights I have seen a set with 2 blown open LED's and 2 shorted LED's. Makes you wonder how that happened. When you check them using a digital meter on DIODE CHECK not OHMS. You typically get between .680 and .740 depending on the brand of LED. Anything in that range should be a good LED. A shorted one shows .000 or .001 of course but I have seen some read around .170 to .250 which are also bad. An LED with that reading can cause the protect circuit to kick in a few seconds after power on. That one LED (or several) are not pulling the right amount of current and the protect circuit is sensing something out of whack and it goes into shutdown. This is why the panel may light up for a few seconds then turn off. Consider not repairing a TV with bad LED's for a Customer. Its too risky and you put yourself at fault if you break the panel. You will also have several hours in it. If someone gives you a TV because it has a bad panel or you already one it then go for it. You can still throw it away if you can't fix it! If you want to check the LED's pull the panel open from the front (carefully, you can break the glass or tear one of the ribbon cables, and remember how it all goes back together each is different), get to the LED strips in the light box and ohm check each LED light. On some models you might have to scratch off a little white paint on the strips to check each LED. Follow the tracings carefully to find the positive and negative. Check each light separately you can't diode check them all in series. They should all measure about the same. Maybe 2% tolerance. If you order LED lights, make sure they are rated for TV back light LED's. I use the High Power LG 110LM 1watt 3528 LED TV back lights. They will cost you around 25 cents each. Other types will NOT work. Many bulbs are rated at 20ma and will blow instantly. The TV LED's will pull around 400ma at up to 5 volts. They have worked well in all sets I repair. You will have to pop the lens off the LED. I use my hot air rework station to heat up the bad LED to remove it. Also if you get the new LED's too hot it will ruin them. I use 247 low temp solder paste that melts at 137C/278F and a hot air rework station set low to around 250C. (yes you heard that right, solder that melts at 278F!) You should be able to melt the paste in less than 10 seconds and you will not destroy the LED. I use a little clear silicone to glue them back down on the edges and center them over the LED's perfectly or you get strange light patterns on your screen! Don't get any glue on the LED itself, just each edge of the lens. If you are unsure about surface mount LED's then look up some youtube videos. While your LCD panel is still out of the TV, turn the set on for a minute and check the lights. Use sunglasses. They will be VERY bright! The light should all be uniform from every angle and if they stay lit up you can put your TV back together! Watch some youtube videos on how to surface mount LED's. It will help a lot!
Cheers.

[Sageman98]

Re: Funai LF320FX4F Power Supply Issue?

Hi, can someone on the forum tell me what the LED strip supply voltage actually should be for this model?

Thanks,

Al

Someone said 21 Volts for the LED strip which is incorrect. I have a working unit just like this on my bench and the back lights are fine. It was given to me but has a cracked screen with partial picture and sound but can't find a panel and it would probably cost more than this TV is worth so I am going to put the parts on ebay. The DC voltage on the LED's (red and black wires going to the LED's) shows 56.2 Volts. Hope this helps anyone.

[toddw65]

Re: Funai LF320FX4F Power Supply Issue?

Toddw65 can you please give step by step instructions on how you did the hair dryer fix?

Sorry, wasn't subscribed to this thread so I didn't know about the thread updates. All I did was take a hairdryer to the power board until it was as warm as I could get it then let it cool and the tv fired right up. Unfortunately I now have it back again. The standby LED is lit but the tv won't power up. Back to the drawing board.

[gator2]

Re: Funai LF320FX4F Power Supply Issue?

Hi I am still having the funai 32 inch LF320fx4f tv no power no standby light problem exactly as here discussed .
I found the service manual, can anybody find a clue with it? I thought
here is the link

type B TV, there is some trouble shooting flow chart but no detailed instructions as to how to check which point of voltage etc. I am think might be the standby voltage of 3.3V is at fault but no able to pinpoint where it is

[ZnsaneRyder]

Re: Funai LF320FX4F Power Supply Issue?

I just repaired another TV. Same Repair. Replaced LED with piece of LED strip, and upgraded two caps to 160V 68uf!

[ZnsaneRyder]

Re: Funai LF320FX4F Power Supply Issue?

As a reminder folks, an LED can either short OR open, and this TV will detect that and shut off. You can find white SMD LEDS on ebay, make sure you get cool white or as close to 6500K color you can.

[readyakira]

Re: Funai LF320FX4F Power Supply Issue?

I have the lf320fx4f with serial number prefix ds1. Trying to locate a place to buy the led strip from... Any ideas?

[budm]

Re: Funai LF320FX4F Power Supply Issue?

The LEDs are connected in series like Christmas lights, if one goes open circuit then the whole string will not light up.
I am not sure about the 17 blinks of the power LED though.

[rlivin]

Re: Funai LF320FX4F Power Supply Issue?

Thanks, I got one bad one in the middle of the strip. Would that cause all the others to be bad? If so i am assuming that is why no picture and power light flashing 17 times?

[budm]

Re: Funai LF320FX4F Power Supply Issue?

You need to test each one using power source to limit the test current o may be 50mA or so or your meter may be able to put out enough Voltage and current in Diode mode to test white LED.
According to the earlier post, it has one LED strip with 16 LEDs on it.

[rlivin]

Re: Funai LF320FX4F Power Supply Issue?

My Funai will not get any picture. I have replaced the power board and still nothing. I get 10.5 volts going to them when i hit the power button it goes up to 45.5. Is that enough? What would be the easiest way to test the leds?

[ron350]

Re: Funai LF320FX4F Power Supply Issue?

Toddw65 can you please give step by step instructions on how you did the hair dryer fix?

[toddw65]

Re: Funai LF320FX4F Power Supply Issue?

FWIW, the hair dryer reflow worked on one I just salvaged. At least so far.

[pbones]

Re: Funai LF320FX4F Power Supply Issue?

I have been following this thread, as I have the same problem with my LF320FX4F (Funai) TV. So far I tested and or replaced all the through hole capacitors (not SMD's). That didn't seem to help. I tried re-flow with the hair dryer trick, it worked twice, but once the two was turned off for a 5 minutes or so it would go right back to the same problem (turn on for 2-3 seconds see the logo and turn off). As in the red led indicator would be in standby (solid red) instead of flashing to start. I tried shorting most of the SMD capacitors (one at a time) but still could not get the set to stay on. I have 21 volts on start up (where the board says 21 v on) and 13 volts at the amp spots where the board says 13 v. The only odd thing I noticed was a couple small SMD's jumping up in voltage after the logo disappears, so the smd caps would measure 21 volts on start up, but then once the logo disappeared the voltage at the cap would spike to 60 volts, and then drain off. Any thoughts or ideas?

[budm]

Re: Funai LF320FX4F Power Supply Issue?

Using variable power supply with constant current setting to may be 50mA or so.

[itronic]

Re: Funai LF320FX4F Power Supply Issue?

ok thanks. i have one not light up when testing it with a diod meter. are they a better way to test it.

[budm]

Re: Funai LF320FX4F Power Supply Issue?

You can use FIVE 1N4007 Diode connected in series to simulate White LED.
https://www.badcaps.net/forum/showth...335#post612335

[itronic]

Re: Funai LF320FX4F Power Supply Issue?

can you jump out the bad led just for test purpose

[ZnsaneRyder]

Re: Funai LF320FX4F Power Supply Issue?

I replaced the LED and the TV lights. Now I just need to find the right LED to replace it.

[ZnsaneRyder]

Re: Funai LF320FX4F Power Supply Issue?

I opened the LCD part of the TV to discover a single blown LED backlight. All the others work, which is why I thought when testing that they were good. Just the one in the center is blown.

These TV's must be sensitive to slight voltage variation of LED, but I wish it didn't shut off the whole set. I wanted to post in case others deal with this TV. I'm guessing the capacitors helped by making the LED voltage stronger, being one is blown or about to blow, it draws more current.