Element ELCHW321 Catastrophic Failure

[budm]

Re: Element ELCHW321 Catastrophic Failure

Yes, that is correct, just do not let the probe slip.

[Agent24]

Re: Element ELCHW321 Catastrophic Failure

do not let the probe slip.

I also advise against any wandering probes - I already did that once myself.

The resultant fireworks may give a good adrenaline rush but they are brief and expensive compared to contemporary gunpowder types and not really worth the lasting headache.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

I'm fairly confident I can do this with the probes as it's an 8-pin ic and only pin 4 is the gate. What kind of results am I looking for exactly ?

[budm]

Re: Element ELCHW321 Catastrophic Failure

To see if it draw at 0.5A or more, you may see the current surge at the beginning then it should drop down below 0.5A.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Well I'm not sure what to make of that test. I had the lamps disconnected as it's the only way I can get to the bottom of the board.

With a voltage reading about 1.3v on the 5v line I switched the probe over to AMPs and switched the meter into the amp range as well.

I was reading 0.00 so I switched to mA scale and now it would read a peak that varied (max about 125ma) but would settle to zero in a matter of seconds. Could only get a reading by removing one of the probes and retouching. Always returned to zero soon thereafter.

What's up with that ?

[budm]

Re: Element ELCHW321 Catastrophic Failure

OK, I would solder the wires to the S and D, connect everything back together, turn on the TV, then short the two wires together to simulate MOSFET on condition, if the switched 5V is OK, then the TV should function, then you will know that the MOSFET is bad.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

I like that idea

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Well yoda, you nailed it. Soldered a wire from S to D and set works beautifully.

Since the 5v supply is switched by the 12v supply do you see any reason why I shouldn't just leave the jumper in ?

[budm]

Re: Element ELCHW321 Catastrophic Failure

That switched 5V must be sequenced on after the 12V is on, otherwise they would not have designed the circuit that way. If you leave the wires connected, the switched 5V will always be present even when the TV is turned off.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Actually it has no problems with the on/off sequence as it is now, but if you're saying it could damage something down the road I will swap out the mosfet.

[budm]

Re: Element ELCHW321 Catastrophic Failure

You need to make it turns on after the 12V is on, we do not want the surprise later and I do not think it is good idea to have the switched 5V be on all the time, they have it turned off when in standby for reason.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Roger roger I will swap out the mosfet in question.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Mosfet V813 has been replaced and full voltage to the 5v line has been restored. Set works as it should now.

Much thanks budm !!

[budm]

Re: Element ELCHW321 Catastrophic Failure

Thanks for the feedback. That was fast, you have the MOSFET in stock? Started on Nov 2013, fixed in May 2014, I am glad you did not give up on it.
Also really to have thanks newtothis for providing the SCH, otherwise we may not have gotten this far.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Well I let it sit for a long while until I bought this power supply instead of attempting to fix the train wreck that the original one was. Thanks again and here's a pic of the landfill "escapee"

As an aside Diane Sawyer just refuses to age !

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Yes of course, thanks newtothis !! To clarify I had the old power supply which I harvested the mosfet from.

This was the first tv I bought to repair after I fixed my neighbours by replacing the main board so I feel sorta like I've come full circle )

[Repler]

Re: Element ELCHW321 Catastrophic Failure

I'm working on this exact board, looking to replace C810, C834, and C808. The schematic shows different specs than the capacitors physically on the board - does that matter?

For example, C810 is on the schematic as 220uF/450V and what's physically on the board is 150uF/450V.

The TV used to work just fine, and these look to me to be the original caps. Should I follow the schematic or just replace what's there?

[Agent24]

Re: Element ELCHW321 Catastrophic Failure

The original design would follow the schematic, but likely they found later they could use cheaper parts in production and get away with it.

You can probably follow either\or. But copying what was already there is probably cheaper.