Hi /diy/
Are electronics hit by lightning salvageable in any way ? I have his receiver or whatever it is here and it was supposedly hit by lightning, but I can't see any visual damage like blown caps, any idea how I can start troubleshooting without damaging the equipment beyond the damage that's already been done or killing myself ?
Pic related, psu of device
>>967896
Lightning is a bitch.
As far as troubleshooting goes, just measure everything that you can.
Start with the diodes, move up to transistors.
The ICs are very likely shot.
These are called varistors.
They are usually connected directly at the mains.
Some times in series with a shunt resistor. When high transients occur, it will route it back, so your circuits are safe.
When the transients have more energy than usual, the varistor will break.
And most of the time if it breaks it will stay shorted.
Measure the resistance across the varistor.
If it is low (5k is still low) it has blown. Desolder the varistor and measure the resistance again. If the resistance is high, you are safe to plug your circuit in the mains and check if it works.
When you measure, remember to check the polarity of you measurements. The diode rectifier may lead you to believe the varistor is broken while it is perfectly fine.
Your circuit will work fine without the varistors.
But if you have a transient again, Everything will break. They cost about 50 cents,
So just replace it.
>>967903
Don't confuse the varistor (connected in parallel with the mains) with an inrush current limiting device like a NTC thermistor which will be connected in series with the mains and should have a relatively low resistance (like 5 ohms). They are in very similar packages.
>hit by lightning
this is a myth, it wasnt hit by lightning because if it was it would have exploded and killed you, do you know how poerful a lightning bolt is? it was a power surge most likely... if lightning hit your house and it traveled thru the electrical system your house would have burned down.
with that out of the way.. unless you have proper tools and knowledge on what each part does to determine what parts are bad.. might as well just shitcan it
>>968088
I assumed everyone knew that I meant a power surge, getting hit by actual lifhtning would be too cool
>>968472
you dont get out much do you...
>>968498
I'm not the one trolling for threads to make pedantic non-corrections on...
>>967896
Bottom left of your pic to the right of the power cord input the round blue thing which is labeled F1 is a fuse. Start there.
>>968499
im not trolling threads, I merely stated that there is no possible "lightning hit" to electronics unless you have them sitting in your roof with a metal rod to attract the ightning bolt, or if your power lines got a direct hit which would either blow out the transformer supplying your house and/or be able to push a considerable surge thru your houses electrical wiring damaging anything connected
but direct hit... not gonna happen
>>969021
So you're saying that past a certain distance from the bolt, the electons expire and don't count as "lightning" anymore?
What distance is that? Who decides?
>>969021
Guy, I don't think anyone here or, indeed, anyone in relatively casual conversation cares about the inacurracy of colloquial jargon. Stop being so pedantic before you hurt yourself.
On the off chance you really don't know, being 'hit by lighting' refers to an electrical surge that exceeds the design tolerance of whatever you're working with. Oftentimes it may not have even occurred when lightning was present, because humans are funny that way.
And you're a robot.
>>969038
He lost his magic blue smoke
>>968410
This is a direct strike. I have the whole path all the way to the main service and the resulting water damage if anyone would care to see?
>>968088
Lol what. Did I had a tree get struck by lighting a few weeks ago. Blew it to bits.
This tree was about 10 meters from my house. And the surge from it fried a crapload of electrical appliances.
Not mention blew all the circuit breakers OUT of my board
Unrelated question.
What is this thing?
I've seen it in many electronic devices.
>>971390
An inductor.
As far a fixing that power supply, you should also check the diodes, they are the black things with a wire on both sides.
They act like a one way valves for electrcity and can fail with a spike in voltage.
They are also cheap to replace like most parts on that board.
>>971441
>An inductor.
Why does a power supply need an inductor?
![Figure_1[1].jpg](https://i.imgur.com/FyH3rGI.jpg "Figure_1[1].jpg")
>>971445
They're the basic component which allows a switching power supply to function.
Inductors resist changes in current with changes in voltage. This can be taken advantage of. By repeatedly cutting off current to an inductor suddenly, you can produce higher voltage. Or, if you want lower voltage, you can use the inductor to slow the rise of voltage applied, turn it off before it reaches full voltage, and the inductor will continue to circulate current until you start to apply voltage again.
>>971390
Common mode choke, part of the mains filter.
It's two inductors on a single core, wound/connected in such way that the impedance to the current drawn by the PSU is low, but impedance to the common mode noise is high.
https://en.wikipedia.org/wiki/Choke_(electronics)#Common-mode_choke
>>967896
I've repaired lots of switching power supplies over the years, and am pretty familiar with their basic topology. Having said that, I am not seeing a "chopper" or switching transistor on the primary (left) side of your board. Are there more parts attached to the bottom? Dollars to donuts, that chopper, wherever it is, is toast. Common repair wisdom states that "The transistor will blow to protect the safety devices."
>>971554
Might be one of those DIP8s. You can get pretty big switchers in that package nowadays.
>>971561
Looking at the 3A diodes on the secondary, I'm guessing the unit has to supply at least 50W. That's a lot of power for an un-heatsunk dip. But, yeah, IC1 is in the right place for it. I'd follow the traces back from the big transformer to verify.
>>971564
Perhaps OP could give us the part number form that chip and we could tell him how to test it.
>>971390
An AC line filter
All power supplies have them.
There are different topologies for them.
So just google it.
