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Re:Ask HN: Tips for Hacking a TV? by purple-leafy on Wednesday October 16, 2024 @01:30AM (#41855906)
Whatever you do, don’t touch the capacitors, especially if it’s an old TV, even if it’s unplugged. Could kill you. Old TV caps pack a serious punch (even when unplugged)
Re:Ask HN: Tips for Hacking a TV? by fewgrehrehre on Wednesday October 16, 2024 @02:18PM (#41862027)
Thank you very much! I will keep that in mind.
Re:Ask HN: Tips for Hacking a TV? by laserstrahl on Thursday October 17, 2024 @02:23AM (#41866933)
Ya, i can relate.
Re:Ask HN: Tips for Hacking a TV? by dommer on Friday October 18, 2024 @06:20AM (#41877946)
Me too. I was about 8 when I took my TV apart and brushed my arm against that capacitor. Packed a wallop, and kept my arm in a ridged state for a bit.
Re:Ask HN: Tips for Hacking a TV? by squidgedcricket on Thursday October 17, 2024 @12:25PM (#41871123)
I think that's no longer true for modern flatscreen TVs. Older CRT TVs had caps charged to a dangerously high voltage, but all the caps on an LED/LCD TV should be a low enough voltage to be touch safe.
Re:Ask HN: Tips for Hacking a TV? by purple-leafy on Thursday October 17, 2024 @05:30PM (#41874010)
Touch safe, how about lick safe?
Re:Ask HN: Tips for Hacking a TV? by throwup238 on Friday October 18, 2024 @04:03AM (#41877286)
That’s what flyback transformers were for. If you licked them, you’d fly back.
Re:Ask HN: Tips for Hacking a TV? by ale42 on Friday October 18, 2024 @03:18AM (#41877054)
Except for the switching power supply, where you have capacitors charged at (rectified) mains voltage so around 155 or 325 volts depending on where you are. They should discharge relatively quickly, but they might be dangerous for a few minutes.
Re:Ask HN: Tips for Hacking a TV? by KaiserPro on Friday October 18, 2024 @06:08AM (#41877871)
Mains will still kill you, even if its not 3.3kv or what was needed to run a CRT.

Its always best to work out where the mains PSU is, and either cover/isolate it so that you don't touch it by accident. Even if turned off, there is a non-insigificant risk that there is either mains power lying around or some other large charge/current ready to bite.

THe back of the inlet is also tends to be a hazard, so be really careful around there too.

Re:Ask HN: Tips for Hacking a TV? by i_am_proteus on Friday October 18, 2024 @06:15AM (#41877917)
Can't echo this enough. If you're working on anything that has been connected to residential mains... use a multimeter. They're cheap! Check the power supply for residual voltage from PSU caps. Discharge them safely before working on the equipment!
Re:Ask HN: Tips for Hacking a TV? by maayank on Friday October 18, 2024 @07:48AM (#41878491)
How do you discharge them safely?
Re:Ask HN: Tips for Hacking a TV? by i_am_proteus on Friday October 18, 2024 @08:18AM (#41878696)
The correct answer is "bleeder resistor."

The other answer is "pliers."

(Make a connection across the terminals that have a voltage difference)

Re:Ask HN: Tips for Hacking a TV? by avidiax on Friday October 18, 2024 @08:57PM (#41884797)
If the maximum voltage is within range, a neon line tester with the button grounded should work well. When the light goes out, the remaining voltage is below the sustain voltage of the neon lamp.

That kind of tester is usually built into a screwdriver and often comes free with some electrical items. They are maybe $2 otherwise.

Re:Ask HN: Tips for Hacking a TV? by implements on Friday October 18, 2024 @08:31AM (#41878796)
Some older flat panels use “cold-cathode fluorescent display backlights” and they’re driven by a high-voltage inverter, I believe - so it’s still a good idea to be wary.
Re:Ask HN: Tips for Hacking a TV? by ta1243 on Friday October 18, 2024 @04:12AM (#41877332)
The UN24H4500 is an LED monitor.

The big risk in old TVs was the enormous voltages in the CRTs (which acted as a capacitor and stored energy even when off, and even pick up energy from background sources)

Re:Ask HN: Tips for Hacking a TV? by BoxOfRain on Friday October 18, 2024 @07:21AM (#41878330)
Aren't a lot of old TVs 'live chassis' as well as using very high voltages?
Re:Ask HN: Tips for Hacking a TV? by mixmastamyk on Friday October 18, 2024 @11:38PM (#41885476)
For faster startup, yes.
Re:Ask HN: Tips for Hacking a TV? by hagbard_c on Friday October 18, 2024 @06:11AM (#41877889)
That may have been true a long time ago in the age of CRT (picture tube) televisions but anything with a flat screen contains a bog-standard switching power supply with a bunch of 450V-or-so capacitors which will give you a nasty bite but not much more than that. In CRT sets it typically [1] wasn't the discrete capacitors which posed a problem but the CRT itself which was used as a smoothing capacitor for the HT power supply. The in- and outside of the back of the tube were (are) covered with a conducting paint (e.g. 'Aquadag' [2], a colloidal graphite coating) with the inside connected to the HT power supply and the outside connected to ground. That 'internal capacitor' can keep its charge for a long time. As to whether it 'can kill you' that seems to depend on a lot of factors ranging from the discharge path, physical condition of the subject and more. There are many reports on people getting zapped who describe it as 'a nasty jolt' but survivor bias means this is not what you should go by - just avoid getting zapped by discharging the tube.

[1] there are exceptions, e.g. older vacuum tube sets which used a mains-driven EHT circuit with discrete capacitors

[2] https://en.wikipedia.org/wiki/Aquadag

Re:Ask HN: Tips for Hacking a TV? by HumanOstrich on Friday October 18, 2024 @07:20AM (#41878329)
TVs that old didn't need to be hacked.