Electronic repair after a voltage spike or power surge

So far I was lucky and never got a lightning strike or other power failure to induce high voltages into my house and equippment.
But over the time I got several requests from friends to take a look at things after literally all connected electronics in their house got fried.
In some cases there is only a total write off as due to a lack of surge protectors inside all unwanted juice made it's way into vital components.
Like a brand new Samsung TV where the replacement of the power board was the only option - which makes you wonder...
But in other cases, like microwaves, induction cooktops, computers and such I had some good success with the repairs.
Guess it comes down to purs luck on both sides, power surge was not too bad and simple components on the input side failed quickly enough to prevent damage to microprocessors or other sensitive parts.

Right now I have an induction cooktop here again that failed after a mains transformer in street blew up during a thunderstorm.
I can tell it was bad as everything in the area of fried parts has a vaporizsed metal film on the surface and not much is left that was a surge protection.
I cleaned all up, replaced the varistors and missing parts of the traces on the circuit board but the cooktop is not performing the way it should anymore :(
At some stage during cooking it turns off with a meaningless error code stating the input voltage was out of bounds.
So my next attempt was to literally remove every single component from the filter and power supply board to measure for any possible connections between the traces.
By doing so I noticed several points where I had a quite high but measurable resistance in areas where there should be none.
Mostly on the direct input side where the varistors tried to save things.
So I used my Dremel in a tin drill press to cut the circuit board aourd the affect areas (where possible with a drill, otherwise with a thin grinding disk)..
Sure enough I was greeted by charcoal colored dust in several areas.
After removing all material until the dust was "clean"  tried again and this time all seems to work fine.

I would like to use this topic to offer some help and guidance in case you have devices that suffered a severe power surge of some sort.
Many of us either have no insurance to replace those items or even if you do the device might be expensive enough to try a repair despite getting it replaced.
Trust me, even it went up in smoke there is still a chance to fix it in some cases and if proper protective circuits were in place the repair could as cheap as a few Dollars for replacement parts.
To get useful advice the following things should be included in your request:
Some clear pictures showing a close up of the affected parts - if there is visibale damage to be seen.
A brief description of what happened, e.g.: lightning strike directly into the house or outside power lines, generator or inverter failure or simply that the power company stuffed up and your entire street was affected.
Of course you will need the means to take the device apart for investigation and also some basic soldering skills or somehow how has and can assist you.
But if you are up to the challange I am willing to help if possible.

gmoon1 year ago

We lost multiple devices (TV, router, switch, computers, even low-voltage track lighting) in a lightning strike a few years ago. Most of it was unsalvageable.

The only guidance I can offer is to physically disconnect (I.E. unplug) stuff, including any TV cable or internet. Or just roll the dice and hope it doesn't happen.

hello! Just had an audio interface go out on me. It's a tascam us800 usb interface for recording audio(music in our case). In our case, we plugged it in and out of a power strip a few times, then it just stopped powering up altogether. Input power says D.C. IN 5V. It looks like it's a little burned inside of the tascam, on the board itself. Here's a few pictures. Please let me know if I left anything important out. Thanks for helping out!

Downunder35m (author)  UPicknChoose161 year ago

The "burnt" spot is normal soldering, something got fixed or added manually after the reflow.
I would first check if the power supply still works and if not get a suitable replacement.