Problem with weller WECP-20

gianmarco

Member
2013-02-20 1:33 pm
Hi I am writing because I have a strange problem with my Weller WECP-20 soldering station.

When I power on it, the led is on, the stylo became hot but a some point it turn off and the tip stops heating. Some times the tip is too cold to solder well, and if it became hot enough it stay hot for a little.

If I point the pot to 350 (with other 100° more avaibles) the station starts going on, it stops, but if I try to increase the temperature the led stay off.

I can't understand why. referring to the official manual I changed the voltage regulator and tested the OP-Amp that seems ok.

Sometimes the solder works, sometimes not, I can't figure out why. The thermal sensor have 25ohms resistance and the resistance of the heating component is 12 ohms.

can you please help me in fugure out what's the problem??
 

gianmarco

Member
2013-02-20 1:33 pm
MM ... unfortunately after couple hours of trying i removed the temperature sensor, connected to the ohmmeter and registered this:

cold: 25ohms

touching with the tip of another solder iron, after something like 3 seconds: overscale

immediatly I touched also with my finger, obviously the tip was barely warm. I figure out the range of the resistance of the sensor is 22 - 58 ohms (more or less) thanks to a trim pot connected instead the sensor and few tests.

Now I connected a 56R resistor instead of the sensor, but I think I need a very expensive (about 40€) sensor.... :( damn..
 
Hi I am writing because I have a strange problem with my Weller WECP-20 soldering station.

When I power on it, the led is on, the stylo became hot but a some point it turn off and the tip stops heating. Some times the tip is too cold to solder well, and if it became hot enough it stay hot for a little.

If I point the pot to 350 (with other 100° more avaibles) the station starts going on, it stops, but if I try to increase the temperature the led stay off.

I can't understand why. referring to the official manual I changed the voltage regulator and tested the OP-Amp that seems ok.

Sometimes the solder works, sometimes not, I can't figure out why. The thermal sensor have 25ohms resistance and the resistance of the heating component is 12 ohms.

can you please help me in figure out what's the problem??

I had the same problem. Most likely the temperature sensor is defective . Check the resistance. When cold it should be ca. 20 Ohms. At 450ºC ca. 56 Ohms. You can buy a new one at Farnell, see:
52641099 - WELLER - TEMPERATURE SENSOR, FOR LR21 | Farnell element14

Cheers, E.