Element ELEFW40C won't turn on.

[Agent24]

Re: Element ELEFW40C won't turn on.

I need the isolation transformer so when I make mistakes like this, I don't get hurt? Or I need the isolation transformer to properly test the crystal?

Also, can you recommend a good isolation transformer that wouldn't need modification that I could use with my scope? Thanks!

It won't stop you getting shocked, necessarily. It means you are less likely to blow up your scope or damage the TV etc.

http://www.toddfun.com/2011/04/30/is..._transformers/ should help. He lists some recommended ones.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

If the clock signal is fast enough and only present for a short time, a DMM may not show anything.

Also, I think we need to see if there's any activity from complete power off, not just button press.

Okay. What I did was hook the scope up to the EEPROM, then watched it and plugged in the TV, then, while continuing to watch it, I pushed the power button. Absolutely nothing. There's an x-tal that says 24.000 on it. I'm assuming that's 24MHz. I have a 100MHz oscilloscope, so I should have been able to see something.

What is the model number of this EEPROM? I haven't seen one before that has settable bits to change the operation behaviour. But I'm sure it's possible. It will still need a clock though, regardless of the mode it's in.

25Q16BSIG. I've posted a link to the datasheet in a previous post. It can be used as single, dual or quad mode SPI, from my understanding of reading the datasheet.

I suppose it could be internally shorted although that kind of failure is more likely with power devices, and would be strange for an EEPROM. I think usually the problem is that some data cells become worn out\stuck and it loses its data in some way or gets corrupted by a 'dirty' power supply. (too much ripple, usually the result of bad capacitors)

Okay, thanks for sharing. And even if the EEPROM was bad, it should still be receiving some sort of clock pulse. I understand digital logic and I understand the purpose of a clock pulse. Without a clock pulse, the EEPROM is essentially dead. What I wonder though is if it should be receiving a clock pulse. Let me give an example:

When the TV works, maybe it works like this:
someone plugs in the TV, there's a standby voltage, waiting for someone to push the on button. Someone pushes the on button, the microcontroller turns the PSU on, THEN the microcontroller activates the clock pulse going to the EEPROM.

When the TV doesn't work, maybe it works like this:
Someone plugs in the TV, there's a standby voltage, waiting for someone to push the on button. Someone pushes the on button but the microcontroller is bad and never turns on the PSU. Because the microcontroller is bad, it never activates the clock pulse that goes to the EEPROM. The circuit for the EEPROM essentially never gets fully turned on.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

If you're measuring a crystal on the main board which is cold side of the circuit, I cannot see how you would receive a shock. Use you multimeter and check what ac or dc voltage you have between those two points.

It is good practice to isolate any set you are working on from the mains using an isolation transformer. Cheaper than a funeral.

It's around 3VDC that's going to the crystal, if I remember correctly. I checked that first before I did anything. The 3VDC measure on both pins. When the board is screwed to the chassis, there's a wire that connects to one of the screws, to ground it. Because I could only have my oscilloscope hooked up to the crystal when the board was in the air, I'm wondering if this had anything to do with it. I used an alligator clip to hold that wire to the grounding pad on the board, I made sure the alligator clip wasn't touching anything besides ground, but the TV's board wasn't grounded to the chassis.

The x-tal is on the cold side.

You are highly unlikely to measure the oscillation of a crystal by direct connection using your oscilloscope due to the impedance and capacitance the scope probe places on the crystal when you connect to it. This is not always the case but it is generally true for high frequency crystals.

I understand that I cannot accurately measure the frequency of the crystal using an oscilloscope, but I thought I could at least verify if the crystal was producing a sine wave. Are you saying I cannot do that? There's a way to calculate the frequency of the crystal using math, if you measure it with an oscilloscope, but it's not the most accurate way. I saw a video on it once. The guy suggested just pulling the crystal and building a small circuit that has a trimmer cap in it or something to allow you to measure the frequency accurately. If you're interested, I can find the video again.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

It won't stop you getting shocked, necessarily. It means you are less likely to blow up your scope or damage the TV etc.

http://www.toddfun.com/2011/04/30/is..._transformers/ should help. He lists some recommended ones.

If I were to purchase one of these (which I'm going to do, by the way), then I'll be able to probe the hot side of a PSU using my oscilloscope or no?

Are there any times I wouldn't want to be using an isolation transformer? Also, you say that by using one, I'd be less likely to blow up my scope or damage the TV. Can you think of times when I would still damage the scope or TV when using an isolation transformer? Are there any definitely don't do this! things I should be worried about?

Thanks!

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

The shock, by the way, it wasn't a bad shock, more like what you'd get from static electricity, but it was constant. There's a little screw on the side of the knob that holds the knob on. This is what was shocking me. I touched it multiple times to verify. It was like kinda what you get when you stick a 9v battery on your tongue, but it was going through my finger. I figured I did something horribly wrong and unplugged the TV, then I turned off the scope and unhooked it, hoping I didn't do serious damage to it.

[Techstar]

Re: Element ELEFW40C won't turn on.

Hi. I have an Element ELEFW40C that won't turn on. There's a solid red power light and if I hit the on button on the side of the television or use the remote control, it doesn't turn on.

I pulled the cover off and the logic board and power board are all one. I've uploaded some pictures, if you need clearer pictures of a certain part, please let me know.

I was going to try and jump start the TV but there's no PS_ON pin. Does anyone know how I can try and force this television on or does anyone have any suggestions on what might be wrong?

I'd like to add that the board bit me when I had the TV unplugged. I removed the case and was trying to remove a connector when I rested my hand on something that had juice. Not really sure what it was though. I'd have thought the 400V capacitor wouldn't hurt because TVs have bleeder resistors and everything. But it felt like a high voltage. It made me swear a little bit. I don't know if that's important or not to mention, but I felt I should say something in case it was.

Thanks!

I once got 25 thousand volts eht through me from a powered up valved tv years ago. Not enough current to kill me but but trust me something i never forgot - Very nasty...

[dick_barton]

Re: Element ELEFW40C won't turn on.

I understand that I cannot accurately measure the frequency of the crystal using an oscilloscope, but I thought I could at least verify if the crystal was producing a sine wave. Are you saying I cannot do that? There's a way to calculate the frequency of the crystal using math, if you measure it with an oscilloscope, but it's not the most accurate way.

No; What I said was that in most cases I believe that you would be unsuccessful.
There are meters on the market you can plug a crystal into for testing.

To be honest I'm sure they fail but the only ones I've ever seen fail is when a leg breaks due to vibration of the circuit board. Not TV's

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

I once got 25 thousand volts eht through me from a powered up valved tv years ago. Not enough current to kill me but but trust me something i never forgot - Very nasty...

I got zapped by a TV with CCFL bulbs. How high of a voltage do you think that would be? I know I woke my wife up swearing! She thought I was dying! I had to work on it while it was plugged in and just wasn't watching where I rested my other hand.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

No; What I said was that in most cases I believe that you would be unsuccessful.
There are meters on the market you can plug a crystal into for testing.

To be honest I'm sure they fail but the only ones I've ever seen fail is when a leg breaks due to vibration of the circuit board. Not TV's

Okay, so I can't even successful test a crystal with the oscilloscope, at least not while it's in the circuit it's in. So you really don't think it's the crystal? I thought it'd be nice to at least see the sine wave on the scope.

[CapLeaker]

Re: Element ELEFW40C won't turn on.

Okay, so I can't even successful test a crystal with the oscilloscope, at least not while it's in the circuit it's in. So you really don't think it's the crystal? I thought it'd be nice to at least see the sine wave on the scope.

Yes, you should see the sine wave on the scope. Just don't connect the probe on one leg and the probe GND to the other leg.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

So I can successfully test the crystal with the scope then? Okay. I'll figure out what leg produces the pulse. What should the sine wave look like? Will a good crystal produce a nice clean image on the scope or will it be fuzzy and jagged and all that? I'll use my x10 probe. I also have an x100, but from what I've read, it's pretty much useless with the scope I have and x10 is the best I can get.

[CapLeaker]

Re: Element ELEFW40C won't turn on.

If the circuit and the ic is OK, you will see the crystal swinging on the o'scope. I do that all the time. 10x probe is fine and that's what I use. I doubt the crystal is bad, but it is possible.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

I doubt it's bad as well. The DMM shows voltage going to it and voltage leaving it. I have a working replacement board coming in the mail. At this point, it's just an experiment so I can learn. When I finish with the experiment, I should be able to safely use my oscilloscope safely to test crystals, I should be able to tell what a good crystal waveform looks like on the crystal, and hopefully, I'll have a better understanding of the oscilloscope and how to use it.

[CapLeaker]

Re: Element ELEFW40C won't turn on.

on youtube are tons of 'how to' do things with an Oscilloscope. Once you have one and know how to use it, you do not want to be without one. I use mine all the time for trouble shooting things.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

on youtube are tons of 'how to' do things with an Oscilloscope. Once you have one and know how to use it, you do not want to be without one. I use mine all the time for trouble shooting things.

Could you give me some examples where you use the scope instead of a DMM? Besides digital logic and crystals, I can't really think where a scope would come in handy. But with digital logic, I'd think a logic analyzer would be more beneficial.

[CapLeaker]

Re: Element ELEFW40C won't turn on.

To check the LVDS signals of a main board, only able to do that with an oscilloscope. Sometimes I check ripple on small capacitors to figure out if one is bad. For audio problems I use a signal generator and the oscilloscope. If I am looking at IC's to figure out if they are dead or not, as an modulation detector for SSB / AM, etc... It all really depends on what you repair the most. Two of my oscilloscopes are 100MHz and I have a small hand held built in a DMM (Uni-T UT-81C). That little one only has 20MHZ, but it's more than enough for power supplies if I am too lazy to drag the isolation transformer out. There are tons of uses . Check a PWM on a SMPS to see if it is switching the Fet or not... blah blah... the list is long. It came in really handy when I built some crazy lead battery desulfators with a voltage doubler circuit with huge capacitors and others that were even more powerful. They would spike the battery so hard, that you could hear it not on the desulfator, but in the battery post itself. But that forum has been not active for a while now.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

Wow, thanks for sharing. I never realized how useful one can be. I want to check the ripple current on capacitors. Why do you only use the scope on small capacitors and not larger ones?

I also want to check a PWM and see what that looks like on a scope. That sounds like a lot of fun. So, what would it look like on the scope if the PWM on a SMPS was switching the field effect transistor? I still have so much to learn. It just blows my mind how much some of you guys know. Right when I think I'm making progress, I'll run across something and realize how little I still know and how far I gotta go.

I still struggling making my own circuits. I have trouble grasping the concept of capacitors and transistors. I've tried learning about them many times now. I just don't really fully understand them. I see schematics that have capacitors in them and I say why is there a cap there? I believe I understand filter caps. Their job is to just smooth the DC output of a power supply, so it's more constant. I believe a rectifier produces pulsed output and a cap can kinda smooth it out a bit. But I couldn't begin to tell you how to calculate what size capacitor to use.

We were talking earlier in this thread about the possibility of a capacitor killing a person. The only thing that seems to matter is the voltage of the cap and the resistance of the human body. The capacitance doesn't seem to come into play at all as to whether a cap is deadly or not. From the little bit that I know, I don't think any run of the mill capacitor can kill a person. I'm sure there's some super caps that can, but I don't think anything we find in modern electronics can. I might be wrong though.

[diif]

Re: Element ELEFW40C won't turn on.

This suggests 1/10 of an amp and 50v DC enough to kill.

https://sciencebasedlife.wordpress.c...efore-you-die/

[CapLeaker]

Re: Element ELEFW40C won't turn on.

There are tons of useful how to do things with an Oscilloscope. There are quite a few good vids on Youtube. Search in Youtube for 'A2AEW', Mr Carlson's Lab, EEVBlog, just to get you started. Remember to be very careful with the Oscilloscope in the Primary side of a PSU, as you are connected to power mains. A normal Oscilloscope's GND on the probe is tied to the Earth pin to Mains and that is again tied together with the neutral wire in your fuse panel. So unless one puts the PSU on a isolation transformer or use a battery operated Oscilloscope, probing the wrong thing in the wrong place is going to sour your day in less than one second.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

This suggests 1/10 of an amp and 50v DC enough to kill.

https://sciencebasedlife.wordpress.c...efore-you-die/

Isn't it just the current that matters? I was under the impression regardless of what voltage, if there's enough current, you'll die. When I was a young child, I liked to put metallic things in my mouth. I had an 8-bit NES would and put the video cable in my mouth. One day, I grabbed the transformer and put the metal piece in my mouth, not realizing it was plugged in. That break the habit that instance! The transformer was 1-amp but I didn't die. For the longest time, I had trouble understanding how 1/10th of an amp will kill a person but when I put that transformer in my mouth, I didn't die. I believe it's because of the very high impedance our bodies have is the reason I didn't die.