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Hear how engineers talk about various "fantasies" about first power-up on PCB.


For a newly soldered board, after confirming board's circuit diagram is correct and checking it thoroughly before powering it up (mostly with a multimeter) - are you still worried about what awesome things are going to happen at moment you power up? the flowers even explode)?

Hear how engineers talk about various "fantasies" about first power-up on PCB.

Complaint version

@pivot point:

The sister paper in lab will ask us to approach board every time board is turned on for first time...

@ Eric Luo:

The main board. In beginning, I always felt that weak electricity would not be dangerous. And then there were two destructive experiments, once mos hit me in face, and once power source flared up. After that, every time I turned on power, I freaked out.

@I will become a giant, stepping on strength, stepping on dreams:

Have you ever seen gorgeous explosion scene of a 1600V 4800uF capacitor? Have you ever seen a real arc discharge scene with a current of 1000 A?

Funny version

@Anonymous user A:

It's like having a girlfriend for first time.

If you pay too much, you'll get used to it and know why it won't explode!


There must be a feeling of fear. Every time I turn on power I find a sheet of hard paper to cover all capacitors. Am I going to say stupid things?

@Anonymous User B:

One of my buddies who was working on an internship project made ten prototypes and they all burned down. So I did not become permanent and quit...

Dangerous Edition


This means that there was more than 200 V at output of coupling voltage regulator due to accidental disconnection of coupling regulator... The voltage-limited 16-volt capacitor directly bulged... fortunately, eyes closed quickly. Slight scratches on outer eyelids, nothing else. In any case, when dealing with electricity, be prepared for accidents, be careful and strict, and ensure lowest possible accident rate.


I'm not an electronics engineer, but I'm into electronics now, usually drawing circuit diagrams, PCB diagrams, generating gerber files, and then making PCBs. One day, boss asked to check if ready-made board could be used, and in order to save time, boss directly asked for a powerful power supply, more than 300 volts.

When I first turned on power, I didn't feel any fear when looking at functions. The boss was worried. I tested it alone, so I asked a colleague to accompany test. The colleague who accompanied test was a graduate student. He saw me test. Lecture me first, you don't want to die, it's all high voltage electricity, you should stay out of line of fire... I said a lot of things that I should have paid attention to, but I didn't.

When I didn't know which board to test, thermistor exploded without warning and sound was loud. I got scared for a moment and it took me over ten secondsd to react. . When I check again later, I will step back one meter before turning on power. Well, yes, it leaves a shadow. I was very scared.

Technical version


Do you want to test strong or weak electricity? If you have strong electricity, you will subconsciously check power switch first. When I turned it on for first time, my hands shook a little. After getting used to it, every time I closed switch or opened air, it was clean and tidy. Once there was a short circuit of battery circuit on circuit board at moment of turning on, there was a loud noise, and after a few seconds of dizziness, immediately check cause of problem.


Actually turning on PCB isn't that big of a deal, until following points are done early on problem won't be a big deal.

1. Check key components, especially polar capacitors, for imaginary soldering, missing soldering, and solid soldering (may short circuit and burn components);

2. Try to use an adjustable power supply, adjust voltage first, and then turn on current slowly when you turn it on for debugging. When you see that current is much higher than calculated one, turn it off immediately and check for a short circuit (or perhaps setting resistor is in wrong position);

3. The next important point is to add a jumper, which is very useful when debugging. I heard from an old senior engineer that a good circuit is 30% design and 70% debugging, so remove jumper before turning on power.


Siege lions, labor is more expensive, but life is more expensive. Powering up PCB is risky and should be done and protected. Be careful and careful when working!