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TV Repair: some days you are unlucky...

DonH56

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#41
A magnet strip (as found on fridge doors) is useful in these situations.
Yah, as long as they are ferrous metal... There were also Al and plastic clips and junk. I have not done TV repair except on my own stuff since college, and not much of that, however.
 

Neddy

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#43
Here's two of such professionals at work.
THAT is HILARIOUS!!!
And neither of them is wearing a wrist grounding strap...that must've stung quite a bit; he did good a hiding it, probably cursed like mad when he got back in the truck:)
In college I worked testing 20-50kv ECL sensing circuits on drift chambers (high energy physics), and even though the power supplies were current limited, I got tagged a few times.
Was fun watching them being installed on the beam line at FermiLab later:)
(Don't let the smoke get out and you'll be fine.)
 

Doodski

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#44
A large capacitor charged to 50 V will make a nice bang if shorted, but it can't directly harm you. You'll feel a slight tingle on wet skin, nothing more.
Wrong ;) I took +/- 65 VDC off some 40,000 micro Farad caps and near broke my arm on my face or was it my face on my arm. I had bent and broken glasses and it made a loud smack sound from the smack that my mates heard and where surprised at. Not recommended. :facepalm:
 

mansr

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#45
Wrong ;) I took +/- 65 VDC off some 40,000 micro Farad caps and near broke my arm on my face or was it my face on my arm. I had bent and broken glasses and it made a loud smack sound from the smack that my mates heard and where surprised at. Not recommended. :facepalm:
That doesn't make sense. If I set my bench power supply to 60 V and touch the leads to wet skin, I feel a very slight tingle, nothing on dry skin. I have only experienced anything resembling the kind of jolt you describe when accidentally touching 240 V mains or higher.

Electrical safety regulations vary, but generally voltages below about 70 VDC or 50 VAC are considered safe in normal circumstances. Much lower voltages can be dangerous if, for example, applied directly to the heart. Secondary dangers like sparks setting off explosions are another matter.
 

Koeitje

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#46
The other problem with using an oven as a soldering tool, aside from it being really broad-area and having a variable temp profile as stated earlier, is that all the food grunge outgasses and can contaminate whatever is on the board, and of course the board can outgas all sorts of nasty chemicals that will bind to stuff in the oven to be deposited on whatever you cook next.
My dad has an oven with Pyrolysis cleaning, there is no food residue in that oven ;).
 
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#47
Got tired of it and picked up a C series LG OLED TV. May still repair it for bedroom use or something.
Would be interesting to see measurements of internal DAC of C9. It has a combined headphone/line out that can be selected from menu to be either.
 

solderdude

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#48
My dad has an oven with Pyrolysis cleaning, there is no food residue in that oven ;).
How hot is the oven set to ?
Solder usually doesn't reflow below 180oC even low temp solder paste needs at least 140oC.
 
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amirm

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Thread Starter #50
Would be interesting to see measurements of internal DAC of C9. It has a combined headphone/line out that can be selected from menu to be either.
Oh. Have to figure out how to get it to play content to do that. Right now, disconnecting it from the main system is out of the question after being without a TV for a few days. :)
 

bravomail

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#51
Got tired of it and picked up a C series LG OLED TV. May still repair it for bedroom use or something.
way to go! I heard some stories about Samsung TVs even when tube Funai TVs were around. Funai rocked! Then I upgraded to Panasonic Plasma, which I still have. OLED should do well. Just watch that burn-in.
 

solderdude

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#52
I don't remember exactly, something like 180c or 190c.
How long would the board be in there ?
Most parts shouldn't be heated for more than 60 seconds.
Certainly for BGA it also takes time for the heat to reach the balls and for them to melt might take several minutes.
 

mansr

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#53
How long would the board be in there ?
Most parts shouldn't be heated for more than 60 seconds.
Certainly for BGA it also takes time for the heat to reach the balls and for them to melt might take several minutes.
And that is one of the reasons why reflow profiles start by pre-heating the board to a lower temperature that is safe for a longer duration before applying a short high-temperature blast to melt the solder without frying the internals of components.
 

Tks

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#54
way to go! I heard some stories about Samsung TVs even when tube Funai TVs were around. Funai rocked! Then I upgraded to Panasonic Plasma, which I still have. OLED should do well. Just watch that burn-in.
Ill second this, don't watch news channels or nonsense with static elements of UI or logos. This is the deathblow that will forever keep OLED out of the computer realm in any serious mainstream capacity.
 

Bombadil

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#55
Get the LG OLED. I had a very hard time giving up my pioneer Kuro plasma but the LG is a better picture. So far (1 year), no burn in. I did buy the extended warranty however.
 

Prana Ferox

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#56
That doesn't make sense. If I set my bench power supply to 60 V and touch the leads to wet skin, I feel a very slight tingle, nothing on dry skin. I have only experienced anything resembling the kind of jolt you describe when accidentally touching 240 V mains or higher.

Electrical safety regulations vary, but generally voltages below about 70 VDC or 50 VAC are considered safe in normal circumstances. Much lower voltages can be dangerous if, for example, applied directly to the heart. Secondary dangers like sparks setting off explosions are another matter.
AC makes the muscles tingle, DC makes muscles contract and keep contracting. DC hurts way worse but both can kill.

NFPA 70e Article 130 gives the limit where you need special electrical safety precautions at 50 volts (AC or DC). That's the common US civilian reference for electrical workers.
 

Don Hills

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#57
Way back when I did my electrical registration course, the instructor set up a demo. We all had to write down a voltage that we thought we could withstand. Then he took 2 pairs of uninsulated linesman's pliers and hooked them to a variac via an isolating transformer. We each had to wet our hands with salt solution and hold the pliers in each hand while he increased the voltage. None of us managed more than 23 volts. It was quite unpleasant, approaching involuntary muscular contraction.
 
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amirm

amirm

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Thread Starter #58
Ill second this, don't watch news channels or nonsense with static elements of UI or logos. This is the deathblow that will forever keep OLED out of the computer realm in any serious mainstream capacity.
It has a couple of interesting features to deal with static content:

1. Detects logos and lowers their luminance.

2. When it detects static video frame, it starts to shift them gradually (about once a second).

Pretty clever signal processing that is possible now, but not a few years ago.

On computer use, I have had an OLED on my main music system driven by a PC for some three years. I don't use it all the time though so no damage. When the new LG puts up help text, you want to cry. It is that sharp and nice!
 

DonH56

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#59
Way back when I did my electrical registration course, the instructor set up a demo. We all had to write down a voltage that we thought we could withstand. Then he took 2 pairs of uninsulated linesman's pliers and hooked them to a variac via an isolating transformer. We each had to wet our hands with salt solution and hold the pliers in each hand while he increased the voltage. None of us managed more than 23 volts. It was quite unpleasant, approaching involuntary muscular contraction.
It's not just voltage, it is current (power) as well... 12 V from a car battery or alternator can be more painful than 20 kV from an old CRT.

At least to some people.

OK, to me.

BTW, AC and DC voltage are different beasts. DC will generally cause one spasm and knock you away; AC can react with the ions in the bloodstream (etc.) and cause muscles to clench and lock up. Low-level AC is used in exercise units for general conditioning and to aide the medically bedridden.
 

Alexanderc

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#60
I’m frustrated for you Amir. Thanks for sharing. I’m glad there is somewhere you can go to vent.

I don’t know if this is the proper place for my story, but it’s about TV repair (a mod should feel free to delete this if it’s not appropriate). About 5 years ago I bought a new Vizio 55 inch TV. A month or two later it developed a serious problem where the picture looked like there was a shadow floating on it. After many emails over a couple of weeks including both photo and video evidence proving there was indeed a problem, they sent two guys out to replace the board. In the process, the two guys managed to crack a trim piece on the edge. It wasn’t visible from the front and purely cosmetic, but every time I walked by I noticed. So I emailed customer service again, but this time no picture, no proof just a message back saying (I’m paraphrasing): “this is a known issue, we will be happy to replace your TV ASAP; however we no longer have the 55 inch model in stock. Would you be willing to take a 65 inch instead?” To which I responded, “sure, that’s fine.” Literally non-functional TV requires proof, gets repaired (not well). Minor cosmetic defect gets replaced immediately no questions asked. :oops:
 

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