Weller WES51 works only at high temperature

Thread Starter


Joined Nov 24, 2016

There're other posts related this issue like this, http://forum.allaboutcircuits.com/threads/weller-wes51.93435/#post-1065641 but no solution found so far I guess.
My Weller WES51 is working only at 75F or higher. It gives me green light but the iron is not getting hot at all until I turn the knob to 75.
I did multiple testing based on the manual, "https://www.scu.edu/media/school-of...-lab-resources/Manual_WellerSolderStation.pdf"
Below is the test result.

Base Check
1. With line cord unplugged and power switch on, check for approximately 21 ohms at line cord blades
2. With line cord plugged in and power switch on, check for 24VAC ±10% between pins #2 and #6 of tool receptacle
- 4.2VAC (#2 & #3 - 27.84VAC, #2 & #4 - 27.84VAC)
3. Check transformer secondary for 24VAC ±10% - 27.84VAC
4. Check wiring from tool receptacle to printed circuit board
- #2-red(bottom), #3-orange(2nd from top), #4-yellow(3rd from top), #5-ground, #6-red(top - J1)
5. Check for continuity from pin #5 of tool receptacle to line cord ground pin

Tool Check
1. Check heater resistance from pin 2 to pin 6 (see Figure 1) of the tool connector, should measure 9 - 11 ohms
- 10 ohms
2. Check sensor resistance from pin 3 to pin 4 of the tool connector, should measure 1 - 2 ohms
- 2.3 ohms
3. Check resistance from pin 5 of the tool connector to tip, should measure 2 ohms maximum
- 0.4 ohms

One thing that's odd to me is #2 & #6 pins measured only 4.2V while #2 & #3 or #4 measured 27.84VAC.
Is this wrong?
The wire connections seem correct.
Can anyone help on this issue?