Weller WHS 40 (analog model)

[smile]

Well I was able to dissemble the Weller WHS 40 soldering station iron to change the cheap insulation wire to silicone insulation. To dissemble the WH40 iron you have to use small flat screwdriver and brake 4 red tabs you can see inside on the front of the handle.

The wire can be changed and everything be put together, you can leave few centimeters of old wire to solder to, because there are nice crimped connections you do not want to remove.

Other then that you put everything together and use hi temp furnace glue Stovex to hold it in place
https://images.clasohlson.com/medias/sys_master/8871330119710.jpg

The glue gets rock solid, adheres to plastic and metal. So no problems either.

My question is about the fact that this soldering iron has 2 core wire, so how does it control the temperature?The The heating element has 3.8ohm value and AFAIK polarity does not matter.

P.S. anyone has schematic?

[nanofrog]

For two wires, the sensor is in series with the heating element. Since resistance changes with heat, you can measure the voltage change for the feedback loop.