Definite fix to Weller EC2002 erratic display and no heat.
OK humanity, here is my present to you. I hope it will save tonns of collective time tinkering with moody Wellers.
As many of you who landed on this page, I have a few of EC2002 inherited from my old job. I love these irons more than any other. Though it does not have auto-shutdown like new once, I'm attached to them, they grown into my hand and nothing can replicate that feel, that perfect temperature when solder flows soft and sticky and when flux creates light haze and amber runoff rather than blackened crust.
Unfortunately, lately, in period of about one year they all, one by one started behaving badly, reading not stable, to the point where it just refused to produced any heat.
Well, as I had a few spares I eventually accumulated a bunch with exactly same symptoms. Time has come to resolve this c#4p.
I opened them and work begun:
Please note that stations I have all with ceramic boards. I've heard about once with PCB and PicChip, like EC51, but never saw them. So this story is about the once with ceramic boards.
First thought, like with most old electronics, was to replace all electrolytics. Did that, all spanking new tantalums - noting changed.
There was plenty of posts around Interweb suggesting micro-cracks in ceramic. I don't think so. These are some of the toughest boards, probably mil-spec.
Anyway, put the one with new caps aside and got next one. This one I did not touch the caps. I went straight to cutting off ribbon, removing board and cleaning it to investigate under microscope for the cracks like described above. I found none.
There was some nasty tape over three sides. I had to remove it and wash. It was very sticky. Board wash was hardly making tape glue slightly softer. I rub it off with my bare fingers and then wash board again to remove my grease. After soldering ribbon back to my surprise station was fully functional, no bad behavior or anything funky.
Yep, it got to be the glue. Got next one. To properly clean it you have to remove board. Trying to unsolder ribbon just stresses pads and melts insulation. It is my recommendation to cut ribbon off, close to the board, trim it neatly then strip it anew and solder it fresh. This way it looks clean and not abused.
As expected by now, third one now works like new.
I went back to the first one, clean it as the other two and got same result.
This is it! You don't even need any replacement parts! Isn't' it great!
TEMPERATURE SENSOR
OK, now you get bonus info: As I was tinkering with it and was getting ready to spend on spare parts I've realized that some info really missing about these stations. Temperature sensor is hard to get and very little info about technology used to measure temperature in these stations to replace them with generics.
If you have your temperature sensor open-circuit, you can make one from what you most likely have at home.
It is simple wire-type PTC. Thermal coefficient of it is slightly less than that of a copper or aluminum.I I'm guessing this is because added constant resistance of cable. Looking at metals electrical resistance thermal coefficient table it looks like many metals will work. Slight error of few degrees will not affect usability of iron. I set temperature by feel anyway.
You can wound one and pot it with high temperature silicone (hardware store, silicon for fireproofing) or other non-flammable cement like non-conductive compound.
When you trim your new sensor, at station terminals it should be 20 to 22 Ohm. It is pretty low resistance, this is why only two terminals have gold plated contacts. Other terminals are not worthy.
I hope this writing will save some of these wonderful, old stations and a lot of your time.
Cheers y'all!
