Element ELEFW40C won't turn on.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

If the cap has charge Voltage of 400V and your body resistance of 40,000 Ohms (80,000 Ohms), you will then have 10mA (5mA) of current flowing through your body (you will feel that!), and after 1 time-constant, the Voltage on the cap will drop down to 63% of 400V.
If you touch the stun gun using EACH hand at each probe, then you have current flowing between two hands and your heart will be in the path of that current flow, the stun gun has probes close together to reduce that chance.
BTW, the CRT power supply may discharge, but the CRT itself can hold up charge for weeks.
Capacitor also has internal leakage resistance (very high vlaue) that cause the cap to self discharge.
I always measure the Voltage on the cap after the power cord is removed, just to be safe, if it needs to be discharged then I use resistor to do that.

Budm, doesn't it just take 1/10th of an amp (100mA) to kill a person? I almost never check the voltages on the cap, I just discharge them, but I have always discharged them after I unhook the cables and remove the board. From now, I'm going to do it the opposite way.

In case anyone's wondering where Budm got the 5mA from, I believe he used Ohm's Law. The formula for amperage is:
I = V / R where I = current, V = voltage, R = resistance:
I = 400 / 40,000
I = 0.010 Amps
I = 10mA

Thinks like wet hands (ie, from sweat) will allow the current to flow more easily and can cause more damage, I believe. Someone correct me if I'm wrong please. Thanks!

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

I will get some clearer pictures and remove the insulator. I'm sick right now. Had a fever of 101.4F, but I'm going to try working on it because I want to get it fixed.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

With regards to a 120uF capacitor charged at 400v, I'm not actually sure. But I'm not going to grab one with one lead in each hand and see if it messes with my heart. Everyone is different though. It might not kill some people but it might kill others. Best practice is to check first before touching.

If you touch both leads with the same finger it will hurt but is unlikely to kill you as it's only going through your finger.

If the thing didn't discharge after 2 hours I am surprised, though, but indeed, it may be indicative of the fault, or just bad(?) design.

I don't think it could have enough amperage to kill anyone, but I might be wrong. I thought it took around 100 amp to 200 amp to kill a person. But somewhere around 10 milliamp is enough for a real painful shock. I was never trying to say I shouldn't have discharged it first. I didn't and I ended up getting hurt because of it, it was definitely a mistake on my part and everything there. I guess that's how we learn though. If I didn't get shocked, I probably would still be discharging the capacitors after I remove boards, rather than before. If the cap was large enough, maybe in the future, I would have died. So I guess I'm kinda lucky, in a way, that I got shocked.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

I busted out the tripod and tooked zoomed in images and some that aren't zoomed in. If these could be done better, please let me know. Looking through them, I'm thinking maybe I zoomed in too much.

Thanks!

[Agent24]

Re: Element ELEFW40C won't turn on.

I don't think it could have enough amperage to kill anyone, but I might be wrong. I thought it took around 100 amp to 200 amp to kill a person. But somewhere around 10 milliamp is enough for a real painful shock.

I assume you mean 100-200mA, 100 Amp + would probably carbonise you!

List here: https://sciencebasedlife.wordpress.c...efore-you-die/
I assume the limits for death will be lower for anyone with a weak heart etc.

I busted out the tripod and tooked zoomed in images and some that aren't zoomed in. If these could be done better, please let me know. Looking through them, I'm thinking maybe I zoomed in too much.

Thanks!

Since the power supply and logic board are part of the same PCB, there will probably be no external PS_ON pin. Instead there will be a track somewhere going from the Microcontroller to the PSU controller.

At first I would check the PSU outputs, I guess there should be a 5v standby rail somewhere.
See the logic-board regulators, and see if the voltages make sense. Probably you should have a 3.3v and 1.8v rail somewhere.

Might sound dumb, but is there a signal from the buttons\IR board?

If you find the PSU controller IC, look up the datasheet, find the enable pin, trace this back to the MCU perhaps?

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

Oh man, yeah! I mean 100-200mA!

I wondered about the heart thing as well. I also wondered about stuff like a pacemaker. I bet that might change the game a bit.

Only marking on the board where I could see any voltages was the 5V down by where a connector is on the side. That connector also says stuff like IR, green, red, etc. I don't think that's what we're looking for though. Now that I have that insulator off, I might have better luck finding the voltages.

What would the PSU controller IC look like?

I haven't checked if there's a signal from the buttons to the IR board. This is why I wanted to try "jump starting" it. It's hard, because there's like one main connector that has a bunch of wires going to it. The buttons go there, a bunch of other things as well. I'm going to have to maybe plug the board in, but have it upside down, to test, so I can see the printing on the PCB.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

What's the best way to check for that signal from the IR board? Just put a DMM on the IR pin on the logic board and GND, set to VDC and just check to see if there's voltage when someone hits the on button? Or should they be using the remote control? I tried with just the button, there's 0.000VDC. When my wife gets home from her appointment, I'll have her try with the remote control. Maybe I should start tearing the rest of the bezel off to get to the button PCB.

[Agent24]

Re: Element ELEFW40C won't turn on.

Only marking on the board where I could see any voltages was the 5V down by where a connector is on the side. That connector also says stuff like IR, green, red, etc. I don't think that's what we're looking for though. Now that I have that insulator off, I might have better luck finding the voltages.

Check voltages at the output diodes of the PSU section. At least one should have 5v on it.

What would the PSU controller IC look like?

Probably just an IC, somewhere in the primary section. May even be as small as a 6-pin SOT, but unlikely. Either under that heatsink or on the back side of the board under the black plastic, since I can't see anything from the current photos.

That said, there is no APFC here it seems, and I don't know if the smaller, diagonally positioned transformer is a standby supply or the LED driver?

I haven't checked if there's a signal from the buttons to the IR board. This is why I wanted to try "jump starting" it. It's hard, because there's like one main connector that has a bunch of wires going to it. The buttons go there, a bunch of other things as well. I'm going to have to maybe plug the board in, but have it upside down, to test, so I can see the printing on the PCB.

Can you get some more photos showing where the front panel plugs into?

What's the best way to check for that signal from the IR board? Just put a DMM on the IR pin on the logic board and GND, set to VDC and just check to see if there's voltage when someone hits the on button? Or should they be using the remote control?

DMM on the input pins should show a change in voltage level somewhere (low\high) when power button pressed. Can't tell for sure which connector.

With IR input, should be a data stream somewhere, probably a different pin. On a scope you can see a pulse train. On a DMM you're probably looking at the voltage changing from Low or High to something around in the middle, say 2.5-3v if it was a 5v line (PWM effect tricking the meter)


Of course this could maybe all be from an EEPROM fault too.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

I made a mistake and had the wrong pins when I was testing the IR one. I was looking at the board upside down and was counting the pins backwards. The IR has 5.19VDC on it. The power button one has a voltage and drops down when I push it, so I'm assuming the button / IR board is good.

I'll check the diodes. I've checked a few and they have voltage, but I don't remember anything that low. I should hit the power button first though, then check the voltages? I have an oscilloscope, but I still haven't fully figured out how to use it. There's always just too much to do and not enough time to do it in. I started playing around with it once but touched the probe to something on a PSU, thinking I could touch the probe to anything and be fine, turns out that's not true. There were sparks and I was lucky I didn't damage the oscilloscope. Afterwards, I was a bit scared to play around with it. I'd like to see the pulse train, just for learning purposes, but that can wait until I fix it.

Here's pictures of where the connector plugs in, front and back.

I'm still learning. Could you go a bit more in detail about these diodes? First off, I'd like to know why they're called output diodes and how can I always identify them? I know what diodes are, but how can I be certain they're output diodes? Also, what are the purposes of these output diodes? I'm going to check the larger diodes, because I know they're for the PSU. I'll check all of them and report if any of them have a voltage of around 5V or so.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

Okay, I think we're getting close to figuring out what's wrong. None of those diodes had a 5VDC. I had some that had a 12VDC and the rest were much higher, some in the 30VDC range, some in the 100+VDC range. But one of them, one of them is very weird. It shows 227.3mVDC but negative when I measure it the same way as I measure the other ones (black on the cathode side shows positive 227.3mVDC (it fluctuates a bit). With all the other ones, the black (or common) on the cathode side shows a negative voltage.

I'm thinking I should now pull that diode and test it. But I'm also questioning at this point if the diode is at fault or if it's something before the diode that is broken. What do you think?

[Agent24]

Re: Element ELEFW40C won't turn on.

If you're getting 5v on the IR pin, then you probably have a 5v rail somewhere, and it's the correct voltage. That's good.

The diodes I call "output diodes" (because they are for the power supply's output rails) are the rectifiers connected to the main SMPS transformer's secondary windings. Unless the power supply has an AC rail somewhere, all output rails from the transformer will (usually) go straight to diode(s) of some kind.

The silkscreen has the primary side labelled HOT and the secondary labelled COLD. This is common terminology.

Yes, measure the voltage at each diode and check if anything changes when you hit the power button


You can't poke just anything with an oscilloscope, at the very least, remember:

1) Scope input has a max voltage rating, don't exceed it
2) Scope probe has a max voltage rating, don't exceed it (this maybe what you did)
3) If you're probing the primary\HOT side\mains side you need an isolation transformer (or differential probe) or things get blown up. You should have an isolation transformer anyway if you're doing that.

[Agent24]

Re: Element ELEFW40C won't turn on.

OK, so the 5v rail probably generated by a secondary regulator somewhere from one of the other rails. 12v and 30v will be your main output rails from the SMPS. Those are fairly typical voltages.

The ones measuring 100v+ are probably the mains rectifier diodes. The ones right next to the word "HOT" right?

Which diode measures strangely?

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

Here's a picture of that diode and where it's located at.

I was probing the primary / HOT side of a power supply. I'm going to look into getting an isolation transformer (or differential probe). Hopefully, they're not too much.

I'll go back and measure the voltage at each diode, then I'll measure it after push the on button. I still don't think this one should show hardly nothing and be jumping around a little bit like it is. I still want to pull it just to check, but you're thinking this isn't the problem?

From my experience, when voltages fluctuate like this, I'm getting close to finding the problem.

**EDIT: I lifted the leg of that one diode. I test it. One way (black on the cathode side), I find around 47Kohm. The other way, it jumps around. First at the 3Mohm, then it goes to OL, then it comes back, and after a while, it's still counting but up to 14Mohm.

Is this normal for it to jump around with one leg lifted? I would have thought it would have been a stable number. The 47Kohm was increasing as well, but not real crazy like, like it was when I was measuring the other way.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

OK, so the 5v rail probably generated by a secondary regulator somewhere from one of the other rails. 12v and 30v will be your main output rails from the SMPS. Those are fairly typical voltages.

The ones measuring 100v+ are probably the mains rectifier diodes. The ones right next to the word "HOT" right?

Which diode measures strangely?

The one in the picture that has a red square around it. I edited my last post too, telling you what the measurements were (when set to continuity) when I lifted one of the legs. I don't know if that's normal, those readings moving around like that.....

[budm]

Re: Element ELEFW40C won't turn on.

That diode and the small yellow inductor and the filter cap laying on its side next to it are for the Boost converter circuit for the LED backlights.
So did you see the backlights even flash on for seconds?

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

That diode and the small yellow inductor and the filter cap laying on its side next to it are for the Boost converter circuit for the LED backlights.
So did you see the backlights even flash on for seconds?

No, I didn't see the backlights even flash for a second. When I plug in the TV, there's a red standby light. I hit the power button, absolutely nothing. No clicks, no noises, no flashes, nothing. It's as if I didn't even touch the button. But I measured the pin for the power button and I can see the voltage drop when I push it, so I know the button PCB is good.

There's some sort of chip by that diode, that looks like a voltage regulator. There's a metal bar over it and it's hard to see. I want to remove that metal bar and check that chip, to see if it's working.

Is that capacitor you're talking about the black one that has glue under it? Also, that yellow inductor....which component is that? I see the yellow component, but I thought that was some sort of small transformer. Now though, I'm pretty sure I was wrong, because on it, I see:

SYRM06Z-L003 1.0
142914 SY

The L003 means it's an inductor, right?

So the boost converter circuit is a DC-to-DC power converter that steps-up the voltage, while dropping down the current, is that right? If so, why do we need to step-up the voltage to the LED backlighting? I'm trying to understand everything, but couldn't a transformer do the same thing? Or even a mosfet?

I'm thinking it's not working, but maybe there's something else broken that isn't providing power. That's a very big diode to have less than a half of a volt DC on it....

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

Also, can't a switching regulator produce a higher output voltage than its input voltage? I understand we cannot produce more power, but we can decrease current to increase voltage or increase voltage to decrease current. Why use a boosting converter circuit? I'm just trying to understand why things are done the way they're done and how everything works.

[vinceroger69]

Re: Element ELEFW40C won't turn on.

I have had a good look and cant seem to find a schematic for this board have you tried freezing the eeprom/spi flash ic just in case its corrupt and causing the fault you have.

[budm]

Re: Element ELEFW40C won't turn on.

No, I didn't see the backlights even flash for a second. When I plug in the TV, there's a red standby light. I hit the power button, absolutely nothing. No clicks, no noises, no flashes, nothing. It's as if I didn't even touch the button. But I measured the pin for the power button and I can see the voltage drop when I push it, so I know the button PCB is good.

There's some sort of chip by that diode, that looks like a voltage regulator. There's a metal bar over it and it's hard to see. I want to remove that metal bar and check that chip, to see if it's working.

Is that capacitor you're talking about the black one that has glue under it? Also, that yellow inductor....which component is that? I see the yellow component, but I thought that was some sort of small transformer. Now though, I'm pretty sure I was wrong, because on it, I see:

SYRM06Z-L003 1.0
142914 SY

The L003 means it's an inductor, right?

So the boost converter circuit is a DC-to-DC power converter that steps-up the voltage, while dropping down the current, is that right? If so, why do we need to step-up the voltage to the LED backlighting? I'm trying to understand everything, but couldn't a transformer do the same thing? Or even a mosfet?

I'm thinking it's not working, but maybe there's something else broken that isn't providing power. That's a very big diode to have less than a half of a volt DC on it....

When LEDs are connected in series to form a string, the total Vf of the string can be much higher than the typical TV power supply putting out for the backlights circuit which around 24VDC, so the boost converter is needed.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

I have had a good look and cant seem to find a schematic for this board have you tried freezing the eeprom/spi flash ic just in case its corrupt and causing the fault you have.

I have not tried that. I wanted to rule out a few other things first. Do you think it's time to try such a thing? I have a can of compressed air. If I tilt it upside down, it'll produce something really cold, but it's highly flammable. Is that a smart thing to do or should I purchase something that's specifically designed to freeze components?

How would freezing a corrupt eeprom / spi flash IC help? What exactly does the cold do that would make it work again?

Thanks!