DeWalt DCD777 dead, driver board fix, TI DRV91680A brushless driver
Автор: Second life
Загружено: 2022-10-29
Просмотров: 1695
This is the happy story of a lonely DeWalt drill, found in the city recycling bin.
The symptom was no power, no blinking led ( not like in the the case for loose battery thermistor connection, where the drill white LED blinks once).
I have seen some video on the net about a dead drill and the cause was those little 2 fuses being blown, I was decided to search for them and check. I used the same paint stripper as in my other videos to remove the white silicon filler used to cover the brush-less driver board.
After searching for the 2 fuses, to my disappointment they were just fine. In the beginning I was not motivated to continue the troubleshooting but I decided to dig further. The thorough cleaning of the driver board was taking a bit of time but the paint remover does miracles to soften the glue, then it's easy to brush-it off.
After that, I could not see any damage to the parts on the PCB and by chance, at one point, when I re-assemble the drill back, it started to work for a little moment, something intermittent. Only once. Driven by frustration, I kept searching. I fund some vague info on the custom brushless chip driver TI made, special for this brushless type of drill. The chip is TI DRV91680A and this chip does not exist in any public datasheet, except this link here: https://www.ti.com/lit/df/tidrgn5/tid...
It is a custom chip that may have been used only for special customers, like DeWalt.
In that datasheet I could see the power for the chip goes also to the Hall sensors on the back of the motor and while measuring voltages on the Hall sensors pcb, I see the voltage was variable, 3-4V. This was weird.
Searching more for the "intermittent" symptom I found the voltage regulator area, poking the parts there, right away I saw those 2 loose diodes, due to a cold joint solder.
After re-soldering them, I tested the the drill, it came back to life! Voltage on the Hall sensors now measure 8 V. The drill seems to consistently be working now.
That is all. Let's save the planet one item at a time.
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