weird NE555 circuit, found in a cordless drill...

[ELS122]

I took apart the switch in a cheap broken cordless drill I had... this one wasn't potted in epoxy surprisingly. reverse engineered the circuit... and drew a shematic...
I could've gotten the NE555 pins wrong by 180degrees... idk, it had no notches on it and I'm not too familiar with IC's, or SMD stuff for that matter...
the SOT package too... it had 'A73' writen on it, so I asumed it was some 2SA73- BJT, and for that too I could've gotten the wrong BJT with a diffrent pinout, since it makes no sense how there's like no grid leak, no collector supply, no emitter drain... it just seems like it it wrong af....

I don't know where the pins connected to the mosfet and the big diode since it fell apart when I got it open.
if it helps the diode was a 6A4, and the fet was a 50N06

[retiredfeline]

2SA transistors are PNP. The VCC feed to the 555 doesn't look right.

[ELS122]

2SA transistors are PNP. The VCC feed to the 555 doesn't look right.

so I double checked everything again and yes I messed up the circuit a bit... here's the revised shematic

but there's still the transistor is just like floating... I see no path to ground from the emitter, are they using it as a diode perhaps? but why?

edit: yes 4 and 8 are connecter... missed that

[ELS122]

so now after looking at it, it seems that the BJT is used as 2 diodes... so it's like a regular motor driver basically...

[mvs]

A7* is BAV99, two diodes in series.
https://assets.nexperia.com/documents/data-sheet/BAV99_SER.pdf

[retiredfeline]

It seems to be some kind of PWM circuit. You should move the resistor network and switch to the left to make it clearer.

[Zero999]

Yes, it's probably a dual diode package, rather than a transistor.

The circuit doesn't look quite right. Pin 4 should go to +V.

Here's a schematic of a PWM circuit with a potentiometer. It should be similar to that, but with a switch and discrete resistors.