Archive for December 14th, 2011

Weller EC1201A Soldering Handle Failure

For the last few days, my trust Weller EC1000 soldering iron (well, station) has been misbehaving: shortly after cleaning the tip, it would become covered in charred residue and slag. Today, the LED I’d hacked across the heater terminals inside the base stayed dark, even though the tip was hot, and then became sensitive to the handle position. Obviously there’s a loose wire inside, right?

So I took the handle apart by removing the two screws on the front plate:

Weller EC1201A soldering handle innards

Weller EC1201A soldering handle innards

The trick to getting the guts out is to push down on the tab inside the handle that locks the cord strain relief block into the handle. After that, everything comes apart with very little force at all.

Contrary to what I thought, the heater is in the tube surrounding the temperature sensor probe. Looking at the connector on the front of the base unit, the key is on the left side and the wires going clockwise from above the key are:

  • Yellow: heater
  • White: heater
  • Black: sensor
  • Red: sensor
  • Green: shield

I would have sworn the red & black were the heater, as they have special-looking brass/bronze/copper colored pins & sockets. Wrong again.

The temperature probe comes apart thusly:

Weller EC1201A temperature probe disassembly

Weller EC1201A temperature probe disassembly

Basically, slide the connector and ceramic-coated sensor out of the back of the black shell, then pull the spring-loaded sheath out the front.

I hoped for a laying-on-of-hands fix, but it was not to be: the tip heats while the LED (which I wired there early in the iron’s life) across the heater power remains off. But the LED blinked on intermittently with slight pressure on the iron’s tip; a bit more poking and prodding isolated an intermittent open-circuit to the ground wire just outboard of the strain relief at the handle:

Soldering iron cable failure

Soldering iron cable failure

A bit more poking & tugging isolated an intermittent high-resistance short (a few hundred ohms, more or less) to a section of cable half a foot from the base connector at the bottom of the cable’s natural loop when the iron’s in the holder.

Unfortunately, fixing all that didn’t restore the iron to life. It seems that the temperature sensor (a thermocouple?) has failed, allowing the tip to heat well beyond any rational temperature. Now that I’m looking, a cleaned solder layer turns blue with oxidation in a matter of seconds and rosin chars instantly. The temperature control knob has no effect whatsoever.

The date codes inside the box show it’s been with me since late 1982, so on a dollars-per-year basis the thing has been a bargain. A new sensor is $60, a new handle is twice that, and I think it’s time for a new iron… at less than the price of the sensor alone, I think that’s OK.