Clone PhoneFix Quick 861DW Hot Air Rework Soldering Station Repair - Blower Fan Fault

This video details the diagnosis and repair of a clone/fake PhoneFix Quick 861DW hot air rework soldering station. Mid-way through soldering, the airflow blower fan (which I usually use at a low speed) suddenly sped to maximum. Returning the handle to the holster to cool down did not stop the fan once cooled as expected, and continued to run at full speed until the mains power was cut.

In this video I look into the fault, which turns out to be with a TIP122 NPN Darlington transistor in a TO-220 package mounted to a small heat-sink. We also look at a few other parts on the circuit board, including the BTA41-800C triac controlling the mains voltage heating element, the CPU, and voltage regulation, though not in much detail.

The repair was to replace the TIP122 part and full functionality was restored. I wasn't able to find a schematic for my 2019 dated unit. Earlier PCB revisions seem to have undergone significant changes and schematics online did not match my hardware. In the end I did not need the schematic, as some educated guesses led us to the solution! A cheap, easy, trivial fix!

[Aug2023]: This unit is a fake Quick 861DW. I have since bought a genuine one, but this video remains for others.

[June2024]: After lending this to a colleague, the unit failed again, this time, with no fan (rather than full fan). The same transistor had failed. I reverse engineered the schematic a little to see what could be causing the issue. The issue is that the TIP122 (Q1) is used as a linear regulator, and thus runs very hot! I have added extra heatsinking! The schematic section is here: https://www.george-smart.co.uk/files/...