Emerson LF401EM5 LED TV no power won't turn on

[Toddo]

My son was watching his TV when it just went blank. The TV is only 2 years old. I know almost absolutely nothing about TV repair/troubleshooting. I can't see throwing away this TV and buying a new one when it probably only has about $4.00 worth of bad components that need to be replaced.

Since I'm getting nothing at all I "assume" there's something bad on the power supply. I went ahead and removed the PS and checked out the tops of all the electrolytic capacitors on the board and they're all good and flat. No bulging at all on any of them. I found a YouTube video and learned that the little black barrel components on the board are not supposed to have continuity and I got continuity on the three components with the red circles. Not sure what those are. The one in the Blue circle is a fuse I think and it has 3 leads and I got continuity between all three leads so I think the fuse is good. I plugged it in and tested the voltage at the power connector hot lead in the purple circle and it read 88.7 volts (I tested it with it still installed in the set with all the connectors on and the main board connected to it). Not sure if that's right or not.



Anyone got any advise what to do next?

[Andrew F. Ali]

Re: Emerson LF401EM5 LED TV no power won't turn on

Look on e-bay and get another board to replace the one you have....There are cases where these boards were repaired after much brain picking and a lot of parts, In my view it is not worthwhile fixing since if just one bad component is missed and new one replaced all of the new ones would 'blow' again...

[dskall]

Re: Emerson LF401EM5 LED TV no power won't turn on

I agree with above post. Buy new board. I am not trying to be mean just practical. To try to lead you step by step explaining the black barrels are diodes, a fuse does not have three leads, 88v on input is not correct but how did you get your measurement and the blue cylinders could kill you. You would be much better off just replacing board. Having said that if you still want help diagnosing. First you need to find out if you have standby voltage if so you will need to force power supply on and check your other voltages and report your measurements.

[Toddo]

Re: Emerson LF401EM5 LED TV no power won't turn on

I agree with above post. Buy new board. I am not trying to be mean just practical. To try to lead you step by step explaining the black barrels are diodes, a fuse does not have three leads, 88v on input is not correct but how did you get your measurement and the blue cylinders could kill you. You would be much better off just replacing board. Having said that if you still want help diagnosing. First you need to find out if you have standby voltage if so you will need to force power supply on and check your other voltages and report your measurements.

I have actually fixed a previous TV I owned about 3 or 4 years ago. It was an Akai 32" LCD TV that had the red standby light on but no power (first HD TV I ever owned). I got on the internet and found that these sets usually have some specific bad electrolytic caps so I took it apart and it did indeed have some badly bulging caps. Went down to the electronics store got the replacement caps (with higher rated voltage), desoldered the bad ones and soldered in the new one's and the TV powered right up. It's the "blue barrels" that are the electrolytic capacitors. I know about those ones. You can visually inspect those for the most part and tell if they're bad. I do not have a tester that will test the microfarens for the caps that aren't bulging to see if they're ok.

I found a site called ShopJimmy that has the whole power supply board for the Emerson for like $54, and then they also sell a repair kit with some specific parts that are known to go bad for like $15.

Board:
https://www.shopjimmy.com/magnavox-a...upply-unit.htm

PS Repair Kit:
https://www.shopjimmy.com/magnavox-a...repair-kit.htm

Looking at this ShopJimmy repair kit, the included items are listed as,
Fuses - 1
Transistors - 2
Diodes - 4
Resistors - 1



I know the white component with the stripes is a resistor because I used to be an electricians apprentice and I was also taking electrical classes at the college in order to get my journeymans card. The stripes indicate the specific Ohms of reisistance. If the component in the red rectangle is not the fuse then I'm guessing the little brown component in the blue rectangle is the fuse? Cause there's only one fuse listed and it's the only component of it's kind and it has two leads.

I tested the power connector with one lead of my voltage tester on the hot power lead and the negative just touching the metal case the boards is attached to inside the TV. It read 88.7 volts.

The only reason I'm reluctant to just go ahead and buy a whole new board is because I'm not sure it's even the PS board that's bad. I really would like to figure out if it is indeed a bad part on the PS board and then figure out which part and replace them. If you wanna help me with it I would be very grateful. I have a pretty decent Weller brand soldering iron with adjustable temp control. If not, would it be possible to just figure out if the PS board is actually bad before I waste money on a new one?

I just wanted to add one more thing. I know not to touch anything on any boards or any electrical components inside the TV with my hand with it plugged in haha. Just to ease your mind.

[vinceroger69]

Re: Emerson LF401EM5 LED TV no power won't turn on

The blue circle is a transistor and if reading between all three leads maybe bad so remove it and retest the red circles are diodes best to unsolder one side and lift a leg and retest the blue rectangle looks like a fuse test the same part on your board and see what it reads
reagarding the 88v reading on the mains connector it depends what you was using as a ground as your working on the hot side of the psu use the negative side of one of the large capacitors as a ground on the cold side of the psu you can use a grouding screw etc.

[dskall]

Re: Emerson LF401EM5 LED TV no power won't turn on

Ok well first you need to plug in power supply and see if you have a standby voltage. Check each pin with neg. on cold ground metal chassis if board is attached to tv.

[dskall]

Re: Emerson LF401EM5 LED TV no power won't turn on

Need picture of your connector that plugs into your main board. I don't see pinouts. Need picture of back of board maybe the pinout is on back. Should be at least one pin with voltage. Well pictures from shopjimmy are not showing pinouts on either side.

[Toddo]

Re: Emerson LF401EM5 LED TV no power won't turn on

The blue circle is a transistor and if reading between all three leads maybe bad so remove it and retest the red circles are diodes best to unsolder one side and lift a leg and retest the blue rectangle looks like a fuse test the same part on your board and see what it reads
reagarding the 88v reading on the mains connector it depends what you was using as a ground as your working on the hot side of the psu use the negative side of one of the large capacitors as a ground on the cold side of the psu you can use a grouding screw etc.

Black Retangle: This part has no continuity. If it's a fuse it's blown.



All 3 legs of this transistor still has continuity:



The 1 diode in this pic looses continuity with leg lifted. The other still has continuity:



And this diode still has continuity with a leg lifted:


Some diodes I test for continuity ring out for a brief second then loose it. Don't know what that's about. But the three I have pointed out had continuous continuity.

I got 91V on the hot lead of the power connector and going to a ground screw on the cold side.

Ok well first you need to plug in power supply and see if you have a standby voltage. Check each pin with neg. on cold ground metal chassis if board is attached to tv.

My power connector doesn't have individual pins. Only hot and nuetral.

Need picture of your connector that plugs into your main board. I don't see pinouts. Need picture of back of board maybe the pinout is on back. Should be at least one pin with voltage. Well pictures from shopjimmy are not showing pinouts on either side.

Power connector directly from power cord: Red Circle
Ribbon cable to main board: Blue Circle
To display?: Purple Circles



Bottom:



Whole thing:

[dskall]

Re: Emerson LF401EM5 LED TV no power won't turn on

Sorry I meant you need to test each pin on connector going to mainboard. You might want to buy the repair kit from shopjimmy and see if that fixes it.

[Toddo]

Re: Emerson LF401EM5 LED TV no power won't turn on

Sorry I meant you need to test each pin on connector going to mainboard. You might want to buy the repair kit from shopjimmy and see if that fixes it.

I will probably give the shopjimmy kit a try first before I buy the whole PSU. I can see plainly where that big 3 lead transistor goes, the brown component which is probably the fuse and that one resistor with the 2 red stripes 1 silver stripe & 1 gold stripe goes. I hope shopjimmy gives me the location of the other 5 components. I want to see what VinceRoger69 has to say first before I order the shopjimmy kit.

With that fuse being blown it should have protected the main board and the rest of the TV components. I feel pretty confident the damage is limited to the PSU at this point.

[dskall]

Re: Emerson LF401EM5 LED TV no power won't turn on

They give locations for were the parts go.

[vinceroger69]

Re: Emerson LF401EM5 LED TV no power won't turn on

i personally agree with post 2 and peplace the power board it only takes one part too be missed (we have seen this before with plasma repair kits that not all parts are included) and all the new kit blew again look on ebay etc as im sure you will be able too get a board a lot cheaper just get one with a returns policy etc if faulty.

[CapLeaker]

Re: Emerson LF401EM5 LED TV no power won't turn on

i personally agree with post 2 and peplace the power board it only takes one part too be missed (we have seen this before with plasma repair kits that not all parts are included) and all the new kit blew again look on ebay etc as im sure you will be able too get a board a lot cheaper just get one with a returns policy etc if faulty.

I agree... that's why I have a variac and a 100W light bulb wired in series trick, so parts won't blow up. All the Emersons I came across that were broken had blown parts on both sides of the PSU. It's always a fet, a transistor, a fuse, some resistors, some diodes and a zener diode.

For the op: You may want to check everything, including those green resistors for proper resistance. Resistors go higher in value or open when bad.

[vinceroger69]

Re: Emerson LF401EM5 LED TV no power won't turn on

i have not got a variac myself but do use a 100w bulb in series after psu repairs if a replacement mainboard is really cheap in this case i would get one so the sets working etc then i would still probably repair the old board as you have more time to test and a working board to compare resistance readings on etc depends too on how the op feels like soldering smd parts too i guess.

[Toddo]

Re: Emerson LF401EM5 LED TV no power won't turn on

i have not got a variac myself but do use a 100w bulb in series after psu repairs if a replacement mainboard is really cheap in this case i would get one so the sets working etc then i would still probably repair the old board as you have more time to test and a working board to compare resistance readings on etc depends too on how the op feels like soldering smd parts too i guess.

I'm gonna go ahead and do that. Get a cheap board then get the repair kit from shopjimmy and try to repair the old board too just for the heck of it.

I appreciate everybody's advise. I feel pretty confident this TV will be back in operation with a replacement PSU and without buying a whole new TV.

Thanks Yall!!

[vinceroger69]

Re: Emerson LF401EM5 LED TV no power won't turn on

sorry i meant replacement power supply not mainboard.

[Toddo]

Re: Emerson LF401EM5 LED TV no power won't turn on

Can someone help my identify this diode:



It's got SB3A0 printed on one side which I found is a SCHOTTKY BARRIER RECTIFIER diode and then it's got the value of 65 printed on the other side. Does "65" mean 65 volts? I'm gonna replace both of these diodes since the ShopJimmy repair kit did not include them and the one still has continuity with a leg lifted and the other one is still suspect. I'm gonna have to order them from ebay and I wanna make sure I get the right one.

Edit: Looking at stuff on the net just now I think the 65 mean 65 degrees celcius. So then does the 3A in the SB3A0 mean 3 amps? So am I looking for a Schottky 3amp 65 degree C diode? What about the voltage rating?

[budm]

Re: Emerson LF401EM5 LED TV no power won't turn on

https://store.comet.bg/download-file.php?id=1701
SB3A0: 100V rating

[Toddo]

Re: Emerson LF401EM5 LED TV no power won't turn on

https://store.comet.bg/download-file.php?id=1701
SB3A0: 100V rating

Thanks

[Toddo]

Can you indentify this noise the PSU is making after repair

So I got all the ShopJimmy parts on the PSU and an additional bad diode that didn't come with the ShopJimmy kit and miraculously the TV powered right up. Got a minor hitch though. The PSU is making this crazy sound haha. It sounds like it's coming from the yellow transformer on the pics above. Can anyone make out what could be causing this. The TV is powering up fine and the fuse isn't blowing. I know some of my soldering was rough but all the connections must be fine cause it's powering up.

There is one diode that I had to replace that did not come with the shop Jimmy kit that I ascertained was bad. I could not find an exact replacement for that diode which was a SB3A0 (data sheet) 3amp 100volt with a IFSM of 80 amps. I found a similar diode on ebay which was an 1N5401 (data sheet). The SB3A0 is 3amps 100volts with an IFSM of 80 amps. The 1N5401 is 3amps 100volts with an IFSM of 200amps.

I can show the location of each part I replaced. I made a video so you can hear the sound the PSU is making here: https://youtu.be/hDMcqKj_uOc

Should I just let that sound go and not worry about it? The sound is not as alarming loud as it sounds in the video as the cell phone is so close to the PSU when I took the video but you can deffinitely hear it. The TV is working.