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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

#31

Post by silon42 »

mrweasel wrote: post #15
glugc wrote: post #2

Opening Amazon and buying a new one is even easier and you end up with a more modern and therefore better product.

I don't completely disagree. VGA should have been removed from monitors 10 years ago. Some companies still buy new monitors and hook them up via VGA. That should be prohibited by labour laws. The image quality wasn't good enough to be used for an entire work day in 2010 and it certainly isn't acceptable today. Tens years ago I argued with a previous boss that it didn't matter how cheap the monitor was, he shouldn't f…

Just like 3.5mm headphone jack. No.

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

#32

Post by wongarsu »

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?

It's just a resistor over the capacitor that slowly draws current from it. Little enough that it doesn't matter in normal operation, but enough to reasonably quickly discharge the capacitor to a safe level when power is removed.

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

#33

Post by bpoyner »

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 had a friend in high school who found it funny to hand unsuspecting people a fully charged capacitor he pulled from a camera flash. This was 30 years ago, before "modern electronics", so the charge lasted longer than a few seconds. Why this never started a fight I don't know.

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

#34

Post by amelius »

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?

This might be a nice feature of a multimeter: discharge mode.

Putting the leads over a capacitor, the multimeter will show the voltage and discharges the capacitor with a constant safe current. Beeps can be used to indicate when the capacitor is safe to handle or not.

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

#35

Post by jonathanlydall »

mrweasel wrote: post #15
glugc wrote: post #2

Opening Amazon and buying a new one is even easier and you end up with a more modern and therefore better product.

I don't completely disagree. VGA should have been removed from monitors 10 years ago. Some companies still buy new monitors and hook them up via VGA. That should be prohibited by labour laws. The image quality wasn't good enough to be used for an entire work day in 2010 and it certainly isn't acceptable today. Tens years ago I argued with a previous boss that it didn't matter how cheap the monitor was, he shouldn't f…

I think these days that you don't really pay extra to have an HDMI port on a monitor. As HDMI is signal compatible with DVI, you can just use a passive adapter if your computer only has a DVI output.

I have considered digital inputs (DVI, HDMI or DP) mandatory for any monitor I have purchased for myself since 2010 and when people ask me for advice on monitors I advise the same.

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

#36

Post by yitchelle »

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…

> the market is literally invaded by rubbish quality capacitors, and swapping a bad quality one with another bad quality one guarantees it will fail again one day

Actually, even a quality capacitor will fail eventually, just not as early as the fake ones. As you have mentioned about the heat, the capacitor will be exposed to it and will fail because of it.

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

#37

Post by LeonM »

bpoyner wrote: post #33
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 had a friend in high school who found it funny to hand unsuspecting people a fully charged capacitor he pulled from a camera flash. This was 30 years ago, before "modern electronics", so the charge lasted longer than a few seconds. Why this never started a fight I don't know.

> before "modern electronics", so the charge lasted longer than a few seconds.

If you take any capacitor and charge it, it'll take quite some time to discharge on its own.

The discharge is usually controlled by a resistor in parallel with the capacitor on the PCB. Removing the capacitor from the board disconnects it from the discharge resistor. So not much "modern electronics" going on here :-P

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

#38

Post by HPsquared »

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?

A charged capacitor has a surplus of electrons on one side, and a shortage on the other. A bleed resistor allows current to flow from one side to the other, balancing the charges on both sides so there is no relative voltage. Q=CV

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

#39

Post by MisterTea »

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…

Aye I remember bringing back a lot of dead monitors, TV's and even a cheap Pentium 4 motherboard by swapping caps.

A place I worked at had a bunch of 19" Optiquest LCD monitors which ALL eventually died from a single bad cap on the power supply board. I fixed every one of those monitors, think it cost less than $10 to order the caps from digikey.

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

#40

Post by jonathanlydall »

I did this kind of a repair job to a couple of Samsung 23" 1080p screens back in 2012.

A friend gave them away since their backlights would flicker making the monitor unusable for the first 10 or so minutes after they were turned on, after which they worked completely fine.

I have little to no knowledge of electronics, but did know how to use a soldering iron. As I recall, I watched a YouTube video and was confident that if the problem was just the capacitors, then I could manage to replace them.

I opened up the monitor, saw two or three capacitors which were clearly bulging and I used a soldering iron to get them off the board.

I went to an electronics shop expecting that someone there would be able to advise on replacements which would work. As I recall one or more of replacements they had available on hand had a different "number" on it, but they assured me it was a higher rating and wouldn't affect use, I don't know much about electronics, but this made sense to me so I trusted it.

I managed to re-solder them on and they then worked perfectly.

Fast forward to today, about 9 years later, and my brother is still using both the repaired monitors. They have DVI input, 1080p resolution and VESA mounts so are actually very decent unless things like >60Hz refresh rate, higher resolution or very good colour accuracy are important to you.

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