Trying (AGAIN) To FIX This Toshiba TV With NO POWER | Revisit

I'm going to have another crack at this Toshiba 42YL863 LCD TV that had no power!

Will I be able to fix it this time?

Hope you enjoy!
Steve

PS. I'm not an expert in repairs at all. I do this for fun, and it may not be the best or safest way to go about repairing broken stuff. I'm pretty good at melting plastic though. Please don't copy me - I'm an idiot.

The magic things I use to break stuff;

Filming Equipment;

[StezStixFix]

Break Yo'self Fool



(this is a spoiler saver, by the way)

[fluxilla]

You may want to consider using a lighter touch on the desoldering gun. You shouldn't need to use any pressure, the solder wicks onto the tip. Hulk smashing it down into the board can damage pads and traces, especially when you're flexing the board. Keep the desoldering iron tip tinned just as you would an iron. They are magic when they work right. This video is over a year old, so I assume you know this by now, but just thought I'd mention it for anyone else trying this at home. :-)

[I_SuperHiro_I]

It’s the Mooing Solder Sucker’s origin story!

And yes I believe those yellow things are high frequency signal transformers. They look a bit shorter than I remember, but idk what else they would be.

Those wire wound resistors are usually employed as oscillation attenuation adjustment in transformer circuits. I suppose it could be for discharge or suppression as well. Hard to tell from here.

[FrankJCarver]

For a man who has no experience on working on TVs, you have done very well. I have some electronic knowledge (enough) to repair most electronic devices. I've been working on an LG CRT TV (dead set) for two months, now and I just can't seem to find the fault. It could be anything, with a TV.

[valkenburgert]

Steve is so relatable, I always slightly panic from a standby light on my television as well.

[Madmanguruman]

The EMI filter is not there to filter incoming power. The switching power supply generates lots of RF noise and the filter is meant to block it from back feeding onto the mains and causing interference on other devices.

[KBUIF]

Steve, look at the value of the resistor before you condemn things. If one side is ground and the resistor is say 2ohms your meter is going to beep to tell you you have a short or low resistance. Remember meters will beep on continuity between a certain range of resistance, possibly for example between 0 - 50ohms. Examine what you are testing!! Also when testing switch mode power supplies you often see what appears to be shorts but are actually measuring the resistance of coils. Yes the coil is short at DC, but it has impedance that is not a short at AC. Remember these circuits are SWITCHING to generate a high frequency across the transformers to give the required AC output voltages that are rectified back into DC to power the rest of the circuits. They use switch mode power supply circuits to reduce the amount of weight and iron cores involved as the transformers can be much smaller at the higher frequencies. Down side is they produce high frequency noise. That noise however is somewhat filtered by the common mode filter chokes at the AC input stage.
You could bypass those input chokes for testing purposes but you should replace if they are faulty to keep the RF noise generated by the SMPS at a minimum and not fed back onto your AC input mains and into your house wiring and other AC powered devices.

[guywilton]

“I do need to go to the pub….”
Wise words and always better to go to the pub after fixing potentially lethal electronics…..
Well done Steve, more learning has taken place !!

[robindebekker]

Ah, the ol' "I don't expect this to work but it does" conundrum. Good fix, you kept at it mate! I would've long given up at some point.

[martijnappeldoorn]

Those resistors are there to limit the current that is flowing through the mosfet or transtor that it is connected to, in this case the source (mosfet) or emitter (transistor).
The higher the current through the mosfet ( and those resistors) the higher the voltage drop over those resistors, if the drop gets to big the ‘current sensing circuit’ triggers an ‘ over current protection’ and switches the gatedrive to the mosfet off.
Similar resistors are found in power amplifiers between the emitters of the powertransistors and the speaker output.

[chromatiCityGame]

In general multimeters beep "short" even with small resistances, because it's "close enough", usually wires and pcb traces etc. add a tiny resistance, but it's still practically a "short" and needs to be classified as one.

[oldguyable]

i admire your courage to try things other people critique you i am the opposite good on you

[pjmelect]

The two 1.5 ohm resistors are current sensing resistors.

[CTCTraining]

Nice video ... more fixes should end with a well deserved pint. 👏
Those were power resistors you were toying with which, on one side of the transformer are a path to ground but presumably the opposite side windings are where the power for the circuitry is taken ... see if you can find the circuit diagram for a similar model board on somewhere like BadCaps or via general googling to help put them in context.
If it was me doing the fix I’d run it as my main tv for a few weeks before passing it on, coils are weak points and makes sense as a point of failure which didn’t kill the fuse, but I never discount collateral damage which might take time to show itself.
Keep up the great work 👍

[ripleysmith]

If that choke has the same part number it should be fine. Those resistors just tied two sections to the board to the same ground where there’s a physical isolation point. It’ll keep the high frequency out of the DC section of that power supply.

[xuniwor]

The real problem could've been the filter/choke only. If the wires are shorting through the base of the coil (where the wires are wound on), then pretty much only the fuse would blow. This also makes sense that it would only blow the fuse when the tv has heated up enough for the short to happen. Also no damage is done to the rest of the TV if the short happens there. On a side note: Usually when there's a short in the primarily side of a SMPS, often the MOSFET is blown and shorted permanently

[andrewdoherty]

The black line across the board is to show the isolation from the 'hot' side to the cold side. A high value resistor and normally a capacitor is used to provide a reference to earth from the hot to cold sides. Dont measure from cold ground side to hot side as they are not the same thing.

[codlinks]

So glad you made a follow up video. I only recently found your channel so youtubes playing your videos back to back for me. I love your honesty when your not sure or don't know what to do. I wish I had your skills as I have a 52 inch tv that no longer turns on too. Love the videos.

[oldb-kenobi]

So here we are in 2023 and I just found the video where you started using the desoldering gun, which has been a mainstay since!

[gb]

You definitely earned that pint! These videos are getting better and better ... keep up the good work. I have to question how much learning is actually going on in the beer school though :D