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A VGA monitor may be easier to repair than you think

cnx-software.com

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Re: A VGA monitor may be easier to repair than you think

#21

Post by Waterluvian »

barbegal wrote: post #18
jeroenhd wrote: post #9

I'm always wary if these guides. If you know what you're doing then yes, replacing a capacitor is a quick fix to give your hardware a new lease on life, but you can get seriously injured or even killed if you mishandled the open power supplies these devices often contain. This guide addresses the danger by saying you need to "wait for a while" without telling you what "a while" is (a minute? 5? an hour?) and how to s…

IEC 60335 and IEC 62368 state that the voltage across the capacitors must be below 34 V in 1 second after the input power is removed. Modern electronics are remarkably safe and I have never heard of anyone being shocked by power supply capacitors in the last decade. Of course cheap electronics sometimes aren't standards compliant and bleed resistors can conceivably fail hence the advice to wait a bit longer if you wa…

What do bleed resistors drain towards if the ground wire has been unplugged by unplugging the monitor?

Re: A VGA monitor may be easier to repair than you think

#22

Post by nathan_f77 »

barbegal wrote: post #18
jeroenhd wrote: post #9

I'm always wary if these guides. If you know what you're doing then yes, replacing a capacitor is a quick fix to give your hardware a new lease on life, but you can get seriously injured or even killed if you mishandled the open power supplies these devices often contain. This guide addresses the danger by saying you need to "wait for a while" without telling you what "a while" is (a minute? 5? an hour?) and how to s…

IEC 60335 and IEC 62368 state that the voltage across the capacitors must be below 34 V in 1 second after the input power is removed. Modern electronics are remarkably safe and I have never heard of anyone being shocked by power supply capacitors in the last decade. Of course cheap electronics sometimes aren't standards compliant and bleed resistors can conceivably fail hence the advice to wait a bit longer if you wa…

I'm working on a project where I may need to open and repair an old device that probably contains some high-voltage capacitors. Would it be relatively safe to do this if I was wearing rubber gloves + shoes, and used a multimeter to check for voltages, and a large resistor to discharge any capacitors? What kind of bleed resistor is typically used, e.g. for old TVs?

Re: A VGA monitor may be easier to repair than you think

#24

Post by eurasiantiger »

nathan_f77 wrote: post #22
barbegal wrote: post #18

Earlier quoted context omitted.

IEC 60335 and IEC 62368 state that the voltage across the capacitors must be below 34 V in 1 second after the input power is removed. Modern electronics are remarkably safe and I have never heard of anyone being shocked by power supply capacitors in the last decade. Of course cheap electronics sometimes aren't standards compliant and bleed resistors can conceivably fail hence the advice to wait a bit longer if you wa…

I'm working on a project where I may need to open and repair an old device that probably contains some high-voltage capacitors. Would it be relatively safe to do this if I was wearing rubber gloves + shoes, and used a multimeter to check for voltages, and a large resistor to discharge any capacitors? What kind of bleed resistor is typically used, e.g. for old TVs?

Just short the positive side to ground to discharge them.

Note: do NOT do this with thin wires and large capacitors / arrays of capacitors, or you may get a hot copper shower.

Re: A VGA monitor may be easier to repair than you think

#25

Post by opheliate »

wiz21c wrote: post #8

FTA: > it was clear what the problem was with a swollen C812 capacitor. > So no need to check anything with a multimeter or an oscilloscope, a visual inspection of the board could immediately detect the issue. I'm looking at the picture. I'm not in electronics and I can assure you it's absolutely not clear to me that this is the capacitor I'm looking for. So what should it look like ? I understand these things someti…

As I understand it, as someone who is also not in electronics, the cross at the top of the other capacitors you can see is designed as a pressure release, it’s a deliberate weakness in the structure of the capacitor so that if it fails, that’s where it will burst. So it’s very likely that if a cap fails, that’s where any swelling will be visible. You can see the cross is distorted/swollen on the failed cap.

Re: A VGA monitor may be easier to repair than you think

#26

Post by [deleted] »

Waterluvian wrote: post #21
barbegal wrote: post #18

Earlier quoted context omitted.

IEC 60335 and IEC 62368 state that the voltage across the capacitors must be below 34 V in 1 second after the input power is removed. Modern electronics are remarkably safe and I have never heard of anyone being shocked by power supply capacitors in the last decade. Of course cheap electronics sometimes aren't standards compliant and bleed resistors can conceivably fail hence the advice to wait a bit longer if you wa…

What do bleed resistors drain towards if the ground wire has been unplugged by unplugging the monitor?

[deleted]

Re: A VGA monitor may be easier to repair than you think

#27

Post by kichimi »

blueflow wrote: post #12
kichimi wrote: post #10

Earlier quoted context omitted.

I do think you should open your mind a bit. Smart TVs are pretty terrific, I can just cast whatever I want across the room and bam, it's on the TV. Friends can come over and share the input. I can lay in bed with nothing but a remote and browse my plex library. I used to go along this line of thinking, and had a "dumb" TV for a long time. I would spend hundreds of hours trying to get a PC/xbmc/kodi setup with a remot…

What you didn't include: the data gathering and the ads. tons of ads. I interacted with smart TVs before, but when i pay for it and it displays me ads in the UI, its an instant return. I'll have none of that shit. And don't get me started on weird bugs that i can't even fix myself. Stuff like my dad's TV randomly outputting 1-2 seconds of audio of the last selected sender /while being turned off/. Audio only, with th…

I don't experience ads with my TV. I don't understand why this is an often repeated point. I've had three so far (due to moving countries), and never experienced this "tons and tons of ads" thing I see people complain about. It's always just been a UI and some apps.

Regarding data collection, who cares? Just get a pi hole if you really care about that.

Also you are describing a fault that can occur with a dumb tv.

EDIT: okay. I found this https://external-preview.redd.it/DcKcaASCdFkfM-eK5pOiu6DIOZb...

I have a samsung TV and I do not see this. Perhaps this is a region thing. I've lived in The Netherlands and the UK and not experienced this.

Re: A VGA monitor may be easier to repair than you think

#28

Post by jstanley »

eurasiantiger wrote: post #24
nathan_f77 wrote: post #22

Earlier quoted context omitted.

I'm working on a project where I may need to open and repair an old device that probably contains some high-voltage capacitors. Would it be relatively safe to do this if I was wearing rubber gloves + shoes, and used a multimeter to check for voltages, and a large resistor to discharge any capacitors? What kind of bleed resistor is typically used, e.g. for old TVs?

Just short the positive side to ground to discharge them. Note: do NOT do this with thin wires and large capacitors / arrays of capacitors, or you may get a hot copper shower.

Preferably connect it to ground through a resistor.

Re: A VGA monitor may be easier to repair than you think

#29

Post by eurasiantiger »

squarefoot wrote: post #17

I've repaired several TVs and monitors, LED lamps, etc. just by replacing bad capacitors, and in a few cases some diodes too, so it's worth trying especially on electronics that would otherwise be thrown away. If you see a TV/monitor going off randomly or a LED lamp starts flashing, pretty sure there are one or more defective capacitors in there. Defective capacitors are a common plague in modern electronics, and the…

Low ESR only matters for PWM filtering capacitors, such as those found in monitor backlight drivers and some switching power supplies’ secondary circuits.

It is not necessary to use such capacitors on the primary side, i.e. when the large capacitor nearest to the mains input dies, just replace it with a normal electrolytic capacitor that matches or exceeds the original’s voltage rating and closely matches its capacity.

Re: A VGA monitor may be easier to repair than you think

#30

Post by amelius »

Waterluvian wrote: post #21
barbegal wrote: post #18

Earlier quoted context omitted.

IEC 60335 and IEC 62368 state that the voltage across the capacitors must be below 34 V in 1 second after the input power is removed. Modern electronics are remarkably safe and I have never heard of anyone being shocked by power supply capacitors in the last decade. Of course cheap electronics sometimes aren't standards compliant and bleed resistors can conceivably fail hence the advice to wait a bit longer if you wa…

What do bleed resistors drain towards if the ground wire has been unplugged by unplugging the monitor?

They don't bleed to ground. Even if the power-chord is disconnected, there still is a circuit between the resistor and the capacitor, and this is where the current runs.
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