A little Black&Decker cordless drill controller problem


Thread Starter


It's a 9.6V drill (bought in the UK - KC9682C, type 2). Pulled the drill apart and the separate MOSFET (I assume!?) in this is blown - sortov obvious as it has a big chunk missing! Then pulled the controller apart (this reads, if I
remember, 9.6V, 20A) - one of those things that spits their contents at you when you disassemble them!! Was gobsmacked that this has a tiny surface mounted insertable white (ceramic?) PCB with ONLY the following: 8 pin IC, surface
bonded pot plus an R each side, one other R, 2 unidentified SMCs (one is a diode I believe). And that's it!!

OK - so what are the goodies?

The 8pin SMC is marked 'CPX94' then separate line '0605' - what IS this??? Can't find it in any of the chip directories.

The separate T220 is a MOSFET because, well, what else would it be (maybe an IGT?). The terminals were all nicely G|D|S as well. And a T220 is NOT something I expect to see a 20A transistor in!

So, replaced the fractured T220 with a grunty MOSFET - and guess what??? It now cycles between off and full with about a 10sec period (my memory?) regardless of trigger position (except that 'full' is really full and 'off' is really off, plus shorts the motor - thanks to a set of mechanical switches).

I'm confused and amazed - can anyone *please* elicidate? Especially - I want to know what IC can do this (it's not a 555 I am sure!??).

Regards, [email protected]

Curt Wuollet

Probably a custom with an opamp and comparator, etc. Must be PWM as
linear would be inefficient. I'll bet if you check National, Maxim
LDI and the other linear houses they would have a generic for this
function. If the surface mount package doesn't match up, get the
dip and put it together on a little piece of perfboard. Or call the
service center and see if you can get the module. A 555 could be
made to do it, but you would probably need a rail to rail opamp
to get the feedback right.



I have encountered a similar problem with a 956 from dewalt. used a 555 and like mosfet IRF 511 working again.