I’m feeling pleased with myself today after fixing a dead hot air rework station. My technique? Whacking things with a wooden stick! I used the same method a few months ago to fix a dead Mac Plus, so it’s proven its worth yet again. What could possibly go wrong?

This technique is useful for electronics that were working fine, then became progressively more flaky, before finally dying completely. If you can coax a flash of life out of it by slapping the case with your palm, or rapping it with your knuckles, then you’re probably looking at a loose connection or a bad solder joint somewhere – but where? How do you find it?

In my case, I had a two year old Sparkfun Hot Air Rework Station that gave up the ghost. It started working intermittently, and would be fine one minute, but the next minute the temperature display would go dark and I’d get nothing but cold air blowing from the nozzle. For a couple of weeks I could usually “fix it” by tapping on the side of the case, but eventually it failed completely. I was prepared to throw it in the trash, but I decided to open it up first and see if I could diagnose the cause of the failure. Inside I found a lot of… parts. There was a PIC, and lots of discrete components, a transformer, and lots of cable harnesses. Nothing looked obviously damaged or burnt. Hmm.

Enter the hero of the story: a wooden stick. With the cover off, I turned on the power, and began gently tapping on all the different components. Do not use your finger or anything conductive to do this! You don’t want to short anything or electrocute yourself. When gentle tapping didn’t accomplish anything, I resorted to heavier force. Hey, it was already broken, so I couldn’t make it any worse! I finally discovered that if I gave U1 a hard shove (that’s the TO-220 just right of top-center in the photo), I could semi-reliably bring the hardware to life. The suspect was identified.

Fixing it proved to be another matter. After removing all the screws, that circuit board still wouldn’t budge. I needed access to the back side of the board to examine and troubleshoot the connections there. Again, I almost gave up and threw the thing into the trash, but persistence paid off. There are two large knobs on the front of the hot air station for controlling air flow and temperature, and it turned out that these knobs actually anchor the circuit board to the case. I had to unscrew the tiny set screw to remove each knob, then unscrew some nuts and other hardware, before I was able to get the board out. Sure enough, there was a cracked PCB trace right at U1. After a quick solder repair, the hot air station is now as good as new. Thank you, wooden stick!