Element ELCHW402 won't turn on

[Noo0b]

Hello everyone.
Thanks or reading.

This TV started having trouble to power on, and after a while it just would not turn on anymore.
From my reading research, it's a common issue.

I tried every solution I found online but its still not good.
The first couple pictures are of the components I replaced.
The next two what they looked like on the board before the replacement.
The following four pictures are from the replaced components already soldered to the power board. As you can see from these pictures, some capacitors have different voltages from the originals, but from what I've read online and technician advice, the big blue cap would be better off with this higher spec and the others would not make a difference. The three legged components have the same spec of the original.
The soldering on the rear of the board does not look the best but seems firm. The big capacitor has some sort of residue on its solder, please check the next 6 pics.
The last picture is from the power board disconnected from the TV.
I followed the instructions from the other posts about this failure, and my results seem preety similar: no 12v on the blue-stripped white cable connector.
I tested the power button on the main board and the voltage seems to drop from 3,3 V to a value above 1 V, most times around 2.4 V.

The readings that I have on the stripped connector mentioned above, with the 120VAC power line connected are:
GND: 0.0 V
GND: 0.0 V
STB: 2.1 V
5V_S: 4.81 V
5V_S: 4.81 V
12V: 0.0 V
12V: 0.0 V
GND: 0.0 V
BR1: 0.0 V
SW: 0.2 V
GND: 0.0 V
GND: 0.0 V
5V_M: 0.0 V
5V_M: 0.0 V
The relay clicks.
The SW voltage was 0.0 V before the parts replacement.
Measurements done with the black probe on chassis.

The readings with the 120VAC power line connected and the stripped cable disconnected are:
GND: 0.0 V
GND: 0.0 V
STB: 0.0 V
5V_S: 4.84 V
5V_S: 4.84 V
12V: 0.0 V
12V: 0.0 V
GND: 0.0 V
BR1: 0.0 V
SW: 0.0 V
GND: 0.0 V
GND: 0.0 V
5V_M: 0.0 V
5V_M: 0.0 V
Measurements done with the black probe on chassis.

The readings with the 120VAC power line connected, the stripped cable disconnected and a 1k resistor between STB and 5V_S are:
GND: 0.0 V
GND: 0.0 V
STB: 0.0 V
5V_S: 4.83 V
5V_S: 4.83 V
12V: 0.0 V
12V: 0.0 V
GND: 0.0 V
BR1: 0.0 V
SW: 0.0 V
GND: 0.0 V
GND: 0.0 V
5V_M: 0.0 V
5V_M: 0.0 V
The relay clicks with the resistor contact.
Measurements done with the black probe on chassis.

I believe here's where my problem branches from the other related posts on badcaps.net.
I have tried the solution that worked for those, replacing the 10uf caps, but it did not produce results here.

If anyone could share advice on what to do next it would be kindly appreciated.
Thanks in advance for all.

[CapLeaker]

Re: Element ELCHW402 won't turn on

with the PSU turned on, what DC voltage do you get on the main filter capacitor? Check out the repair kit for this PSU at SJ. There are some IC's involved and SMD resistors too.

[Noo0b]

Re: Element ELCHW402 won't turn on

Hi CapLeaker,
Thank you for your reply and the kit tip.
The big capacitor was at around 200 VDC right after plugging in the AC cord, then slowly discharged.
Measured with each prong at the correspondent cap terminal at the rear of the PSU.
Isn't 200 V a bit low for a 250 V capacitor?
Kind Regards and thanks again.

[budm]

Re: Element ELCHW402 won't turn on

The BIG MAIN FILTER CAP (black round cap with 450V rating on it) will not have DC on it until the power relay is turned on until the STB (PS-ON) signal is received from the main board.
https://www.badcaps.net/forum/attach...4&d=1528240407
Please provided better focused pictures of the whole top and bottom side of the board, I have a hard time reading any prints the board.

[Noo0b]

Re: Element ELCHW402 won't turn on

Hi budm,
Thank you for your reply.
I noticed the capacitor would not charge without the main bundle connected.
A computer jumper shorted STB to 5V and the voltage on the main cap was 221 VDC.
Capacitance was 0 uf. Also tried with the probes inverted on it's terminals.
The power switch did not change STB from 2.1V, and the reading on the STB leg of the 1k resistor connected to 5V was 3.3V.
I took a bunch of separate pictures of the board, that was the best I could do. I added the pictures from another OP with the same issue, newuser65, since they have far better quality, thanks for him. I Also included the schematics for the board, Thanks to R J for that.
Kind Regards and thank you all again.

[budm]

Re: Element ELCHW402 won't turn on

How did you go about measuring 221VDC on that main filter cap? Where did you put the meter probes?

[CapLeaker]

Re: Element ELCHW402 won't turn on

yeah... these 221V DC on the main filter cap do not make any sense. What exact cap did you measure (C903)?

[Noo0b]

Re: Element ELCHW402 won't turn on

Hi,
Thanks for the replies.
Sorry for this, I guess I should have remembered that the main filter cap is near the power terminal. I measured C810 instead.
C913 is at 175.3VDC with the probes to the corresponding terminals on the underside of the board.
The PSU's main connector STB was jumped to 5V with a PC jumper.
Thanks again.
Best regards.

[budm]

Re: Element ELCHW402 won't turn on

I just look again at your reported Voltage readings:
The readings with the 120VAC power line connected, the stripped cable disconnected and a 1k resistor between STB and 5V_S are:
GND: 0.0 V
GND: 0.0 V
STB: 0.0 V
5V_S: 4.83 V
5V_S: 4.83 V
12V: 0.0 V
12V: 0.0 V
GND: 0.0 V
BR1: 0.0 V
SW: 0.0 V
GND: 0.0 V
GND: 0.0 V
5V_M: 0.0 V
5V_M: 0.0 V
Something is not making sense, if you do have have 1K resistor between 5VS and the STB pin then the STB pin should not be showing '0 V'.
You did indicated that the relay does click, if that the case then the PFC Voltage booster circuit is not working since you only see around 170VDC on the main cap with forced on resistor, so need more in-depth troubleshooting in PFC section.

[Noo0b]

Re: Element ELCHW402 won't turn on

Hi,
Thank you for the reply.
Good point.
Multiple rechecks indicate a consistent 3.3VDC reading.
Since no repairs were attempted since that reading, it's probably missing a paste edit.
My apologies.
Best regards and thanks one more time.

[Noo0b]

Re: Element ELCHW402 won't turn on

I noticed that R815 is getting a bit hot and R807 is warm to the touch right after jumping STB to 5VS.
I believe those are 5.6k Ohms 5% resistors.
They are connected in series with resistance "1" if measured separately and "0" if measured at the external terminals.
Here's what they look like:

[Noo0b]

Re: Element ELCHW402 won't turn on

I'm not sure which cap I should have measured.
The biggest cap, located between the heatsinks, C810, is rated 250V and reads 221VDC.
The smaller cap located nearest from the power terminal, C913, is rated 450V and reads 175.3VDC.
Here's what they look like:

[budm]

Re: Element ELCHW402 won't turn on

C810 in the schematic you provided is rated at 220uF 4500V which is the for the PFC Voltage booster circuit filter cap.
I do not see C913 in the schematic.

[Noo0b]

Re: Element ELCHW402 won't turn on

Hi budm,
Thanks for the reply.
I checked the schematics and C810 is rated 220uF 450V indeed.
All the other OPs with this board issue report a 250V C810:

I think the PFC of 220VDC is OK since the cap C810 is only rated at 250VDC.

The cap measured is C903, as CapLeaker mentioned.
My apologies for this.
Its rated 450V and reads only 175V.
If that's an indication of a defective cap, I'll try to find and replace it again.
Thanks again and kind regards.

[Noo0b]

Re: Element ELCHW402 won't turn on

C903 replaced.
No changes, still at 175V

[R_J]

Re: Element ELCHW402 won't turn on

When you jump 5V_S to stb, I suspect the relay turns on (clicks once)?
This is a universal input power supply rated 100-240v input, thats why the 450 volt cap. for standby, I take it in hell you have 120 volts a/c? so voltgae on C903 will be 160-175 vdc
The voltage on C810 should be 400vdc if the pfc is working
Check the voltage across C814 (22uf/50v) in pfc circuit (stb jumped to 5v) and then VZ812, It should be 18 volts on the zener and maybe around 25 volts on c814

[Noo0b]

Re: Element ELCHW402 won't turn on

Hi,
Thanks for the reply.
The relay clicks alright.
All voltages measured at 120VAC.
Its worth noting that everyone seems to be confused about C810.
The schematics report a 450V Cap
Every other OP with this board @ badcaps.net have a 250V 390uF cap, check my pic.
C814 was replaced along C811 and C812 before the OP.
Check the first picture on the OP and C814 is the fist to the left of the bulged blue poly cap.
C814 readings oscilate from 11.45VDC to 11.77VDC, prongs at the terminals and STB jumped to 5VS.
I had a hard time finding VZ812, so i took my chances and assumed it was VD812, by the PFC circuit on the schematics.
It appears to be marked DAO0 SEF1506.
I measured it with the STB jumped, meter set to 20VDC and the meter beeped intermitently.
I inverted the polarities and it beeped a bit as well.
I changed the meter to Diode mode and the moment I touched the anode with the probe a big flash happened at the rear of the board and the fuse is busted.
Hopefully it's the only damage I caused.
Please look at the picture below to see what it looks like.
Thanks for the attention and best regards.

[CapLeaker]

Re: Element ELCHW402 won't turn on

Yeah, ok... that’s why there are some weird measurements. First off, when you do measurements with the PSU powers on, you only measure Volts AC and DC. For capacitance, resistance and diode mode, the PSU is unplugged!

I am thinking the PFC isn’t working, because you have no boosted voltage. Check that diode you just fiddled around with for a short. If its shorted, replace it. Check the fets on the PFC for a short. If they are shorted to the gate of the fet, check the driver circuitry too.

[R_J]

Re: Element ELCHW402 won't turn on

Here we go again... Why would you check resistance with power applied? Not only did you damage the power supply, you likely damaged your meter.