Problem with weller WECP-20

[gianmarco]

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??

 

[DUG]

Try 360C-365C setting.

 

[gianmarco]

no matter the temperature, my 350 in the first post was in example. The heating stops too early.

by the way, I tried also with 360, 365, no differences.

 

[gianmarco]

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..

 

[gmphadte]

I had one of these iron without the station. I connected one constant current source initially, but later connected 15 Volts dc laptop PSU. I have another iron that gets very hot for difficult jobs, and this is now kept for pcb duty only.

Gajanan Phadte

 

[Edmond Stuart]

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.