Electronics > Repair

When I heat the PCB, the voltage becomes constant.


Hi everyone. I have a question for you. I've Lınak motor controller PCB. This PCB was working 3.3 voltage not became constant. This value has changed between 2.8 - 3.3 at begin. After 10 min. later this voltage became constant. I checked all soldering part IC components. I never found trouble on PCB.
I noticed a pic of the PCB and the location indicated by the green circle this location when I was hit with a hot gun this place the PCB worked as well.
Thank you!


Electrolytic caps could be bad

Use a wooden stick to push on the components and PCB in that area and see what changes. It may be just as easy to resolder ("reflow") all the solder joints on the components in that area. Also, check closely for a crack in the PCB, or a trace. Please remember to post your solution, when you find it.

Wallace Gasiewicz:
I have worked on a lot of things with your particular problem. Pushing on the board with a stick sometimes helps but you flex the board and the problem may be across the board and somehow the pressure you put on this part of the board will fix the problem that is really elsewhere. I still do the stick thing, even if it is not perfect.
There could be a solder failure on one of the components or a microscopic crack on a trace.
Here is what I would do:
Re solder the caps, if the solder looks bad, remove it and re solder. Sometimes the through hole connections on these connections are not good and the solder does not reach the top of the board from the bottom, where you solder it.
Look for small cracks on the traces  and surface mount component solder joints with high magnification.
Replace the caps (cheap enough)
It is possible that one of the surface mounted components is the problem, but less likely than just a bad connection.

Remove that light brown "glue" that's used to hold the electrolytic capacitors, sometimes that material can absorb humidity and become slightly conductive.
It can also hide electrolyte leaking from the bottom of the capacitor or from the top.

Inspect components and make sure there's no bad solder joints.


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