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Beginners / Re: PC restarts after shutting down
« Last post by JustMeHere on Today at 07:09:42 pm »Yeah, if it's that old, you got a bad battery.
Recent Posts
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Repair / Re: Question about Dual supply power supplies and shorting
« Last post by Kleinstein on Today at 07:07:51 pm »With a short between the +12 V and -12 V the weaker side could see a reversed voltage.
Ideally the circuit and / or supply PCB should have diodes that limit the reverse voltage to ground to something like 0.7 V. Most circuits can survive this.
If a bit paranoid one may add such diodes (e.g. 1N400x, or 1 A shottky), at least for the tests.
With a larger ciruit (many parallel OP-amps) the test current from the diode mode can be a bit on the low side. The 200 ohm range resistance measurement is usually similar (e.g. 1 mA range).
Testing OP-amp pins to the supplies is at least worth a try, as quite some semiconductors fail short.
Ideally the circuit and / or supply PCB should have diodes that limit the reverse voltage to ground to something like 0.7 V. Most circuits can survive this.
If a bit paranoid one may add such diodes (e.g. 1N400x, or 1 A shottky), at least for the tests.
With a larger ciruit (many parallel OP-amps) the test current from the diode mode can be a bit on the low side. The 200 ohm range resistance measurement is usually similar (e.g. 1 mA range).
Testing OP-amp pins to the supplies is at least worth a try, as quite some semiconductors fail short.
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Test Equipment / Re: Portable Oscilloscopes List (cheap)
« Last post by globoy on Today at 07:03:03 pm »The FNIRSI even has a FUNCATION soft button! 
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General Technical Chat / Re: What do you WANT to buy?
« Last post by themadhippy on Today at 06:59:49 pm »Quote
I want to buy are simply gogglesa face shield/visor is a better option, protects more of the face and dont fog up like googles
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Test Equipment / Re: Siglent SDS804/814X HD or Rigol HDO914S for Mechatronics student
« Last post by Fungus on Today at 06:59:17 pm »I think the Rigol's easier to use with WiFi. Just a $7 USB dongle.
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General Technical Chat / Re: Why does the US provide all critical electronic design knowledge to the world?
« Last post by themadhippy on Today at 06:56:22 pm »Quote
That's why (almost?) all modern democracies are representative democracies, whereby we elect our preferred representative and they do all the grunt work on our behalf.maybe another of the greeks ideas would work better,get rid of elected politicians and replace them with a team selected by random,bit like how jury service in the uk works.
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Beginners / PC restarts after shutting down
« Last post by Z. Khalid on Today at 06:53:07 pm »Hi all,
I have an issue related to an industrial tablet PC with Windows 8.1 installed. This PC keeps restarting by itself after approximately 10 seconds of shutting down when the power supply is not connected (when it is running on the battery). Replacing its SSD with a new one having Windows 8 fresh installed (to figure out whether the fault is OS related) didn’t help.
Have any of you guys encountered such an issue?
I have an issue related to an industrial tablet PC with Windows 8.1 installed. This PC keeps restarting by itself after approximately 10 seconds of shutting down when the power supply is not connected (when it is running on the battery). Replacing its SSD with a new one having Windows 8 fresh installed (to figure out whether the fault is OS related) didn’t help.
Have any of you guys encountered such an issue?
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General Technical Chat / Re: Submersible missing while visiting Titanic wreck
« Last post by dietert1 on Today at 06:51:31 pm »Verifying a safety factor of 2.25 or 4 would have meant pressure tests beyond 8 000 m. It never happened.After whistle-blowing happened there were enough people who knew the design was marginal. Somewhere above i already wrote that in mechanical engineering safety margins of 10 or 20% are very unusual, especially if human life is at risk. Safety checks cause delays and cost money. I think that business wasn't viable as it was nonsense from the very start.
Regards, Dieter
They thought they had a safety factor of 2.25 on the hull, which is something they should have been able to achieve given that the demands on a 5" thick hull 66" outside diameter is only 35,600 psi in hoop stress compression. the us navy did a lot of work on this in the 80's and some of their E2 fiberglass hulls had 110K psi compression strength, even though the samples tested were curved sections cut from the hull and compacted in a press.
I can't seem to find reliable data on the viewport. Stockton actually claims he was 8% off the charts and had a safety factor of 4 on the viewport, in the released transcript of Lockridge's interview. But the manufacturer said we'd only certify it for 650 meters. if you take the usual factor of safety of 6 or 7 for viewports.. this is consistent with one expert's testimony that the veiwport would last "a few dives to 4000 meters" (650*7 is 4550)
a factor of safety 4 viewport would have been more like what you see on the subs that have gone down to 36,000 feet.
Regards, Dieter
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Test Equipment / Re: Portable Oscilloscopes List (cheap)
« Last post by Fungus on Today at 06:50:56 pm »Oh, the FNIRSI comes with a cute carry case, I'm sold!
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Test Equipment / Hantek dso2d15 Noise from internal power supply
« Last post by iw2evk on Today at 06:49:39 pm »Hi,
somone have tried to modify internal circuit of dso2d15 for reduce the radiofrequency noise irradiated from scope?
I've placed a ferrite sleve on main cord but it's not sufficent for reduce noise.
All around the scope for about 1mt i've strong radio noise on wide spectrum frequencies.
need help , please
Roberto iw2evk
somone have tried to modify internal circuit of dso2d15 for reduce the radiofrequency noise irradiated from scope?
I've placed a ferrite sleve on main cord but it's not sufficent for reduce noise.
All around the scope for about 1mt i've strong radio noise on wide spectrum frequencies.
need help , please
Roberto iw2evk