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Electronics => Repair => Topic started by: hoei on May 07, 2020, 09:52:40 am

Title: Weller AG701 Hot air solder station
Post by: hoei on May 07, 2020, 09:52:40 am

Pump is working, but heater wont come on no matter the temperature knob setting.

I've dissambled the cable connector for the pen, and was surprised to find only 3 wires going to the pen. Two black wires, apparently for a 5 ohm heating element, a white wire for chassis. Also there is a small PCB inside the connector (see reverse engineered schematic). Adjusting the potmeter makes no difference.

Interestingly, I am able to make the lamp come on (albeit dim) by connecting a 1K - 5K6 resistor over pin 3+4

- Has anyone experience with this device?
- Is it even worth bothering with a solder station without a proper temperature sensor? I wonder how the regulation is done.

Title: Re: Weller AG701 Hot air solder station
Post by: hoei on May 08, 2020, 11:24:25 am

Ok, so took the case apart and found out that the temperature control pot is not getting any supply voltage at all. It is connected to a transistor T1 (only TO-92 on the board) which seem to be a darlington. Marking is "bl" , "C617".

Anyway, I didn't get much further because suddenly the 8V dc supply blew up, so now I have to replace one of the bridge diodes and the 8V regulator L7808CV.