Fuzzbox, Distortion, Phaser, Chorus, Echo and other Guitar Effects Info

Not related to pedals or audio, but… I have a couple of the 18v Drillmaster cordless drills from Harbor Freight that I bought years ago during one of their sales. They are crappy drills but still useful on occasion. However, the battery charger has died and HF does not sell them anymore.

The wall transformer was definitely burned out and it looked like some components inside the base unit were also defective. However, after a few minutes of poking around with the ohmmeter on the tiny pcb in the base, I decided that all of the parts were okay and that the hand-soldered smt parts were just covered with nasty flux residual. I cleaned the pcb with a swab and some alcohol, measured the parts values to confirm they were good, and drew the schematic while I was looking at it with a magnifier.

Amazon had a replacement wall power adapter but it was a switching power supply and not a transformer type that came with the original drill. I bought it anyway and when it was delivered, I connected it to the cleaned-up base unit and put a battery on the charger. The proper lights came on and it seemed to be working. After a couple of hours, I put the battery in the drill and it was definitely charged (at least partially).

The circuit in the charger base is very simple, and uses a PNP transistor to switch on a red LED when the unit starts charging. When the voltage on the battery gets high enough, the PNP turns off and the LED goes out, however, the full voltage is still being sent to the battery. This means that it should be monitored and the nicad battery pack removed from the charger once the red light goes out.