Star Digital Ski Wax Iron Repair

[logscool]

Alright so this one might be a bit different from the usual test gear and typical consumer products.

So I have a Star digital Ski waxing iron used for waxing nordic and downhill skis (nordic in my case). These are some of the best irons on the market and hold temperature very nicely. The other day I went to use mine and plugged it in only to have nothing happen. I was pretty sad  .

I have made a repair to this iron in the past when the rotary dial broke. That was quite a simple job and after ordering the part I was back up and running shortly.

This time the Iron displays no sign of life when plugged in and I am not quite sure where to start.

I've attached some photos of the different components in the iron.
There is a BTA12-600C Triac, an IEC 60384-14 X2 capacitor, and both the main board and the display board have Atmega48 20AU chips.
I understand that there is some half wave rectification happening which is then controlled with the Triac to feed the heater but that's pretty much the extent of my knowledge and I'm unsure how to troubleshoot this issue.

If anyone can help me better understand what to check and what might be going on that would be great!

[Armadillo]

I would suspect the X2 cap. Take it out, measure it and replace it.
It forms a AC voltage divider with the big resistor. It either open or high ohms.

[logscool]

Ok I pulled out the X2 I'm not very knowledgeable in measuring capacitors but on my multimeter it measures overload on resistance.

On my LCR meter at 1kHz I measure 841 nF and an ESR of 0.01 ohms

[Armadillo]

Seems like the cap is OK, opps! not this time around.
Then the next suspect is the big resistor.

[logscool]

Measuring the resistor in circuit with the cap removed it measures exactly 220 ohms which is it's rated value.

[Armadillo]

Only a handful of components on the board.
My last shot will be the 2 diodes, soldering and broken copper tracks.

[logscool]

Both diodes test fine with 0.53v on the silicon diode and 0.69v on the germanium diode and both testing overload when reversed. I also tested the smaller electrolytic cap on the board and it measured 380uF with an ESR of 0.3ohms (theta -84. at 120Hz, it's rated at 470uF.

Visually I don't see anything wrong with the soldering or the copper tracks.

Is it possible that something happened to the micro controller and it isn't running properly?

[Gyro]

Daft thought, but I don't see any reference to you having checked the heating element continuity? 

Edit: The temperature sensor and the pot could also be suspects.

[logscool]

I did not check that because I figured it wasn't even trying to supply current to the heater. Just checked it and it measures 15.3 ohms.

However I just soldered everything back up and it now powers on again!

I believe the main board is actually one that I had pulled out of another iron that had intermittent problems with not turning on before. I thought it was just due to some loose connections at the time and swapped it because this board is configured to heat up to 180C instead of 170C which can be helpful for some of the very high end fluoro powder waxes.

Glad it's working now, any thoughts on where an intermittent fault might be would be helpful. Perhaps it was one of the solder joints I redid.

[Gyro]

That's promising, I just edited my post above - either of those might possibly cause intermittent operation. Even something as silly as a damaged cable near the entry (check continuity while flexing). Not all faults turn out to be electronic, especially intermittent ones.

[Armadillo]

kkkkkkk LOL 
Did I say soldering and broken tracks?
I discover some micro cracks can only be seen in a microscope, and some hidden below solders.
Sometimes, try moving the components, you can see the cracks lift up.
Best is to resolder all joints, "reinforce" it if necessary and clean contacts.

Edit: BTW I hate the board. Look at the tracks, I think is auto-routed using a width of 12. Kind of Silly especially for power lines.

[logscool]

Awesome thanks for all the help guys. Hopefully it'll be reliable in thew future now. Great tip on the resoldering and reinforcing solder joints!