LF501EM5F No Power, Chirping/Beeping Transformer

[jason123]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

C3214 is shorted on these main boards its underneath L3201 above the black ribbon connector. It took me 5 hours and a hot air gun but finally cleared the short from P-ON+21V to ground. Hopefully nobody else has to go through that, I can still hear the diode check beep in my sleep. Sets will power on now, I haven't found a replacement yet but will keep you posted.

Put small like sized cap from part graveyard in place of C3214 and is working perfect again.

You saved me hours of troubleshooting. Replaced the cap and the TV fired right up. Thank you very much!

[Microbot118]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Okay! I got it the C3214 cap out. Now I am getting some resistance off this cap off the board.. does that matter?
C3208 which is still on the board and in parallel with the C3214 I removed was previously coming up with no resistance. Now it has some resistance on a higher setting of my multimeter. What other troubleshooting can I do to confirm and where can I source a replacement cap from?

Thanks!

Sorry for the late reply, just turned notifications on so I should be more punctual.

It's hard to say definitively if the resistance on the removed c3214 matters, but if parallel caps are no longer shorted it looks like progress to me. If you want to check that the short is really gone, the easiest way would be to clean the board to get any residual flux removed, then measure the resistance between the 2 unoccupied pads from c3214.

Rather than trying to source a new cap, I really just found a visually similar looking cap with approximately the same footprint from a junk board and it worked.

However, this was a free tv for me so there was no risk involved. I'm not sure what your situation is but I wouldn't recommend this method if this is for a customer or something.

[akk944]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

I tested it in place as a preliminary check. It read 0 ohms, but as Bud mentioned earlier there are other caps parallel to this one. If one reads short they all read short until the culprit is removed.

Once I removed c3214, I verified that it was short off the board and the other remaining caps read correctly in circuit.

If you are new to (de)soldering I would highly recommend getting some flux and braid, and clean well with isopropyl alcohol before plugging it back in.

Okay! I got it the C3214 cap out. Now I am getting some resistance off this cap off the board.. does that matter?

C3208 which is still on the board and in parallel with the C3214 I removed was previously coming up with no resistance. Now it has some resistance on a higher setting of my multimeter. What other troubleshooting can I do to confirm and where can I source a replacement cap from?

Thanks!

[Microbot118]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Microbot,

Did you remove C3214 to check for the short... any way to check it without removing it? I still have this TV sitting in my living room.

I tested it in place as a preliminary check. It read 0 ohms, but as Bud mentioned earlier there are other caps parallel to this one. If one reads short they all read short until the culprit is removed.

Once I removed c3214, I verified that it was short off the board and the other remaining caps read correctly in circuit.

If you are new to (de)soldering I would highly recommend getting some flux and braid, and clean well with isopropyl alcohol before plugging it back in.

[akk944]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Microbot,

Did you remove C3214 to check for the short... any way to check it without removing it? I still have this TV sitting in my living room.

[Microbot118]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

C3214 is shorted on these main boards its underneath L3201 above the black ribbon connector. It took me 5 hours and a hot air gun but finally cleared the short from P-ON+21V to ground. Hopefully nobody else has to go through that, I can still hear the diode check beep in my sleep. Sets will power on now, I haven't found a replacement yet but will keep you posted.

Put small like sized cap from part graveyard in place of C3214 and is working perfect again.

+1 on C3214. I have a model LF551EM5 that wouldn't power up, power supply board chirped when plugged in. Sure enough C3214 was shorted. Different main board than OP but similar layout. Swapped with a cap from a junk samsung phone main board and it's back in action.

[akk944]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Delete

[akk944]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Looking at your picture, so how come C3214 is not removed yet to find out if the shorted circuit go away or not when C3214 is removed?
As you can see it is also connected in parallel with smaller cap C3208, c3207 3209 are not installed.
Since the cap is still in place, please check resistance between GND and P-ON +21V to see it shows really low resistance, more likely that your board version use C3214 for the P-ON+21V power supply line, we need to verify.
If it is connected to P-0N+21V line then it will be 4.7uF 35V (min) and it will be the same circuit that RJ provided..

....one year later, Quarantine has finally given me time to look at this again.

Not sure how I figured that the short without the 3214 removed. I'm looking at it now and I checked the resistance across each cap nearby and compared it to the C3214. All of them are extremely low compared to the C3214.

However, I did get 536 ohms when I checked resistance between the C3214 and ground as described in your pictured. All the other caps nearby are right around 600 ohms when grounded the same way. Not sure the relevance of doing that, but I thought I'd throw that out there.

Nearby caps I checked: C3213, C3205, C3212, AND C3211

Does this confirm the C3214 is bad or do I still need to remove it? I will go ahead and remove it if that's the next step, but want to make sure there is no further troubleshooting that can be done with it on

Thanks!

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Budm, no I'm not sure which pin is not connected to circuit ground. I was trying to figure that out by trying either end. I don't THINK my C3214 is in parallel with anything else, but it's hard to tell. I could be wrong. Please see picture of my board and C3214 attached. Finally, my meter has 20M, 2000K, 200K, 20K, 2000, 200. When I put it on the 20 or 200, it doesnt look like I have any sort of connect between AMP +13v and the resistor. Just shows '1'... doesn't even move. This changes when I go to the higher settings.

Thanks!

Looking at your picture, so how come C3214 is not removed yet to find out if the shorted circuit go away or not when C3214 is removed?
As you can see it is also connected in parallel with smaller cap C3208, c3207 3209 are not installed.
Since the cap is still in place, please check resistance between GND and P-ON +21V to see it shows really low resistance, more likely that your board version use C3214 for the P-ON+21V power supply line, we need to verify.
If it is connected to P-0N+21V line then it will be 4.7uF 35V (min) and it will be the same circuit that RJ provided..

[akk944]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Put Meter on 20 or 200 Ohms scale, put one meter probe on the AMP +13v point, another probe on C3214 that is NOT connect to circuit GND (you know which pin that is, right?), if it shows around 1 Ohms or so then that C3214 is the filter cap for the AMP +13v power supply line.
270pf will not be used for power supply filter cap, too small of capacitance.
As you can see form RJ schematic, they will usually put more then cap in parallel as needed, if you trace out one end of the C3214, you will see that is connected in parallel with other caps that may or may be not installed on your board.
The blank PCB can be stuffed to make many PCBA for the needed model of TV, so if the cap is not installed in particular PCBA then the schematic will label that part as 'Open'.

Budm, no I'm not sure which pin is not connected to circuit ground. I was trying to figure that out by trying either end. I don't THINK my C3214 is in parallel with anything else, but it's hard to tell. I could be wrong. Please see picture of my board and C3214 attached. Finally, my meter has 20M, 2000K, 200K, 20K, 2000, 200. When I put it on the 20 or 200, it doesnt look like I have any sort of connect between AMP +13v and the resistor. Just shows '1'... doesn't even move. This changes when I go to the higher settings.

Thanks!

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Put Meter on 20 or 200 Ohms scale, put one meter probe on the AMP +13v point, another probe on C3214 that is NOT connect to circuit GND (you know which pin that is, right?), if it shows around 1 Ohms or so then that C3214 is the filter cap for the AMP +13v power supply line.
270pf will not be used for power supply filter cap, too small of capacitance.
As you can see form RJ schematic, they will usually put more then cap in parallel as needed, if you trace out one end of the C3214, you will see that is connected in parallel with other caps that may or may be not installed on your board.
The blank PCB can be stuffed to make many PCBA for the needed model of TV, so if the cap is not installed in particular PCBA then the schematic will label that part as 'Open'.

[akk944]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

budm,

I don't need to check from the power board right, I can just put one end on the AMP +13v of the main board and the other on the non grounded side of the resistor. What result am I looking for? It appears I have a short on one side from AMP +13V to the C3214 I am looking at, but it's tricky for me because I am a noob and have a digital multimeter. The only thing I tested was resistance from one end of the C3214 to the other and it seems to be significantly higher than any other resistor on the board (.30 on the 20M setting vs.01 on most of the other resistors). My board is a BA31T0G02013 so the schematic that R_J provided does not seem to help, but I could be wrong.

Your help is greatly appreciated!

[R_J]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

I looked up a BA4GU5G0201_3 board and schematic, See if this helps, in this case they use a 4.7µf , The other version board are likely slightly different.

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

1) Measure the dimension of the one you remove to see if it match the dimension of the replacement or not.
2) To verify if we are talking about the same C3214 or not, you need to check the resistant of the Not Grounded leg of the C3214 pin and the AMP +13v jumper wire of the power supply board, do the same against the ALL +3.3V jumper wire of the power supply board.

[akk944]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

If it's 10uF that I need, then how does this cap look?

https://www.mouser.com/ProductDetail...SnPCSGjIcIU%3D

[akk944]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

It is power supply filter cap so it will be 10uF not 270pf.

Ah so what's the cap citywidetvtech is referring to? I just want to be sure I order the right part before I spend 6 bucks on a 10 cent part. Of course, I could order both, but I don't want to mess anything up by using the wrong cap. Please let me know!

Thanks

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

It is power supply filter cap so it will be 10uF not 270pf.

[akk944]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Hello, I'm having the same issue and have found the C3214 cap on my main board. What is the best way of confirming this cap is the problem before swapping it out with a multimeter. Do I need to check for the short as previously mentioned (got a little lost with the hot air gun).

Thanks! Sorry to bring up this old thread.


EDIT: I have a bad cap at c3214! confirmed by checking and comparing resistance with other caps on the board. With this being said, does the following look like a reasonable replacement? Original states 270pF while budm mentions 10uf?

https://www.mouser.com/ProductDetail...KDppzeEQ%3D%3D

[Mr repair]

Re: LF501EM5F No Power

hi guy,s working on a way to proof that the main CPU is bad on Emerson lf501em5f
i have a test for this butt need more info LOOKING for a service manual this for a set
with no stby led butt has stby on supply and if you force on supply all rails are up jump bl-on led,s are on need the manual

[freakytiki4u]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Thank you so much Budm! You rock!