DIYbanter - View Single Post - Using a Thermal Gun / Infrared Thermometer for electronics

mike[_22_]

On 5/9/2017 8:23 AM, wrote:
On Monday, May 8, 2017 at 8:21:14 PM UTC-4, mike wrote:

With the seek, you can find the shorted cap on your laptop
board by putting a little current thru the power trace and
see
where the heat stops. I had one laptop that was driving me
nutz. Turned out there was a cap hidden under some other
component that was bad. It was a .1uF cap. Those rarely
short. I would never have found it without
the thermal imager.

I've seen a lot of those little smd film caps short recently on TV mains and tcons. I don't have an imager, but I give the circuit board a dose of freeze spray, feed in a limited current to the shorted line, and see where the white frost blanket thaws first. With any luck, it's the actual component that thaws first. Problems arise when the offending shorted is close to zero ohms and some feeding component gets hot.

That's why it took me so long to find that one.
It was absolutely, positively zero ohms. It shut down the power supply
instantly.
I had to tap into the correct branch of the power distribution and
apply current there to generate any heat.