Element ELCHW402 - Will not turn on!

[pineapple]

Hello all!

My mother in law bought an Element ELCHW402 a few years back. About two weeks ago, the unit would only turn on every so often. A power cycle or two from the wall, and it would fire up. When it was on, there was no picture distortion or other issues. When it powered up, it worked just fine.

Neither the physical (loosely...its a heat button I think) button nor the remote will turn the unit on!

She called up up a few days ago to say that the TV wouldn't power up at all now. I did a quick google search before going over there to pick it up. It seems that others have swapped a few caps or replaced the entire power board to achieve success.

Symptoms -

1. The plug in - There is an electromechanical click when the unit is powered up with all the boards attached to the power supply. Attempting to remove the connectors to the other boards and then plugging the unit in will not energize the contactor.

2. With the unit in standby, I get 5V and 3.3V on the proper rails, but cannot get a reading on 12V, 16V, or 24V.

3. A thorough examination of each capacitor on the power board shows no physical abnormalities. I have a cap meter that gives me a nice output in farads, but it is at work unfortunately... A quick check for opens shows nothing out of place.


Considering that I can't get the unit to even try powering up completely, what's the next step? It seems that the power supply is ready to turn on but either can't or isn't being told to. I would find it odd that both inputs (the buttons and the remote) would go bad at the same time... The circuits that power them aren't in the same place and seemed to be traced separately.

Thanks to all for reading!

[budm]

Re: Element ELCHW402 - Will not turn on!

Please take good closed up pictures around the connectors so we can read the lables for each pin. We are looking for PS_ON signal which comes from the main board and fed into the power supply board to turn on the 12v/24v power supply.
Please read my basic LCD TV troubleshooting guide.

[pineapple]

Re: Element ELCHW402 - Will not turn on!

Thank you for your reply! I will take a look and try to snap a pic!

EDIT:

Here's the pic as requested. I see from the pdfs you linked that the PSU on signal is activated by just pulling it high and not a complicated rise/fall sort of deal.

I don't see PS_ON specifically...


Also an edit2: The circuitry for both the IR inputs and the button inputs looked linked. May make more sense.

[budm]

Re: Element ELCHW402 - Will not turn on!

OK it is the pin number 3 'STBY' (counting from the right of the connector XP805 which has white/blue stripes) is the control pin that will turn 12v/24v on and off.
So put the black probe of the meter on the chassis, red probe on pin3, check it with the TV plugged in but not turn on, and with TV turn on. We are looking to see if the voltage on that pin will change state (some TV uses >3V for ON, other may use <1V = ON), if it does, then we know the moan board sending the ON signal OK.

[pineapple]

Re: Element ELCHW402 - Will not turn on!

I checked that pin 3, and with the TV plugged in and off it reads 1.1V. 5V logic, anything below 2.5 should cut it for a low. The unit won't turn on, though. I can't check the second spec. The 5V reads 4.98V, so I'm almost positive that isn't the issue. There is also a LED on on the front of the unit when plugged in.

It just sits there with the standby light on. Won't turn on via remote or panel button! Seems really strange...

[pineapple]

Re: Element ELCHW402 - Will not turn on!

I did a few more tests, here are the results:

With a meter between STBY and chassis with 120V plugged in: 1.1V
Same setup, but with a finger tapping the power on button: No change 1.1V (no movement from my analog needle here)

Checked a few + cap legs and other easy to get to test points to see about 5V on the mainboard, and they all read between 4.92V and 4.98V.

Checked the small 0402 resistors by each connector, and they all check out around 2k ohms (they aren't screened with a value...). That seems logical for a currlimit res on that logic trace.

The mainboard isn't sending a turn on signal. Can I jump STBY to 5V to turn the unit on? EDIT: Tried and failed. No change.

[selldoor]

Re: Element ELCHW402 - Will not turn on!

Hi Can you post a pic showing the legend for the connector with the different coloured wires to the right (in your picture) of the one with the white and blue wires

[pineapple]

Re: Element ELCHW402 - Will not turn on!

Hi Can you post a pic showing the legend for the connector with the different coloured wires to the right (in your picture) of the one with the white and blue wires

That is the 24V bundle going to the backlights I believe. The legend is straight forward.

[selldoor]

Re: Element ELCHW402 - Will not turn on!

Yes,I see what you mean. As Budm says some tvs the pson is operated by
pulling the voltage down so 1.1 on the pin may be correct or it should be high.

You can pull it low using a 1 kohm resistor from pin to ground or
to take it high I would use a 3v battery, but yes you can use the resistor to the 5v.

[pineapple]

Re: Element ELCHW402 - Will not turn on!

Thanks for the reply!

I have attempted to pull STBY high by using a 1k ohm resistor to 5V, and the same to low with GND. No change. I don't feel like the resistor is pulling stby high enough, i still read around 1.1V. I am inclined to think a logic HIGH will turn on the power supply as without the blue/white bundle plugged in, that pin reads flat while the 5V_S pins still read a nice 4.98V. Also, without that same bundle plugged in, the power supply doesn't energize the tall, thin relay with that satisfactory click.

[tom66]

Re: Element ELCHW402 - Will not turn on!

Try using a 100 ohm resistor.
A common fault with this model is the blue poly-film capacitor in the middle of the PSU.

[pineapple]

Re: Element ELCHW402 - Will not turn on!

Are you talking about the large film 1000V cap? It can be so hard to tell with those caps, i'll take it off and give it a thorough examination. I will also run by work and grab my esr meter if I'm not satisfied with the ohms result...

[tom66]

Re: Element ELCHW402 - Will not turn on!

Yes, that one. But you can't check it with an ESR meter. For that device capacitance is sufficient.

[pineapple]

Re: Element ELCHW402 - Will not turn on!

I pulled it off and checked for ohms. Open and open! I only have a pretty terrible radio shack meter at home right now, so I'm not entirely sure I'm convinced this is the issue...

[tom66]

Re: Element ELCHW402 - Will not turn on!

A good capacitor will test open, too.

[pineapple]

Re: Element ELCHW402 - Will not turn on!

Thanks for the refresher! My last long term job had a lot of ceramics and electrolytics...

I will have to wait to test that film cap... I did pull most of the electrolytics off for a quick check, and they all acted the same as their counterparts of the same value.

Pulling stby high to 5V with a 100ohm resistor made no change. I will try again with a ten then call that idea shot. No activation of any other power rails.

[pineapple]

Re: Element ELCHW402 - Will not turn on!

Some more information:

Probing the touch button 4 wire input into the mainboard shows perfect signals. Each button sends a different analog voltage, and it returns to normal after the button is released. So the button inputs are not the issue. Running the same test, but checking STBY, shows no pulse or any change whatsoever. I still have no idea where the issue lies!

Also to update, STBY reads about 2.10V (not 1.1V) consistently. My meter had one old and one new battery... doh! Anything above 3V has the same reading as before.

[pineapple]

Re: Element ELCHW402 - Will not turn on!

Sorry to triple post, but I was able to figure out what was going on here.

After jumping STBY to 5V for the 5th time or so, I heard a soft but rewarding pop from the speakers. Realizing that this meant one of the power rails had to be active for at least some human comprehensible amount of time, I isolated the power supply from the other boards, and hard jumped STBY to 5V_S. With the meter + on 12V, I saw the needle quickly jump to about 10.5V, and the quickly fall to 3V or so and falling slowly to 0V. So... the smps isn't functioning properly. Better than the mainboard failing!!!

My hvac buddy is bringing me his nice meter today, hopefully it's just a cap or two...

[whatusername]

Re: Element ELCHW402 - Will not turn on!

continuing where he left off i have the same tv and need to find that blue poly cap anyone know where i can find it and what is the actual value of it? or even better a part number?

Edit nevermind found a youtube vid with a mouser part number 505-M10.047/1000/10P in case someone needs it in the future

[whatusername]

Re: Element ELCHW402 - Will not turn on!

A common fault with this model is the blue poly-film capacitor in the middle of the PSU.

hi all i was given this same model tv with same symptom. i also saw the youtube video on it and the tech had 2 with exact same symptom and problem resolved same way with a new poly cap. i went to mouser with his part number and ordered 2 but turns out they are on back order till august.
mouser part number 505-M10.047/1000/10P and link http://www.mouser.com/ProductDetail/...mvdoxmUNrRPA==
but today while i was working i searched fleabay for 1kv .047 uf cap and came to a set looking similiar ending in a few seconds so i immediately purchased it. but now i notice the ones i bought say .047uF 1kV 1000v 10% WIMA MKS4 http://www.mouser.com/ProductDetail/...w/%252b0LzlQ== Guitar Tube Amp Amplifier Capacitors while the one in his video says MKP10 and im thinking they may be different than the ones i need. so can someone tell me where i can get the correct ones in stock besides mouser? i cant find them