On Mon, 24 Oct 2016 11:18:20 GMT, Johnny B Good
wrote:


Looking at the picture, I can't see any signs of a triac (nor any place
on that PCB where one might lie hidden from view unless it's mounted on
the reverse side).

The black rectangle with a heat sink in the side above C2, what is
it?

The circled area marked "RV1" looks like this Variable Resistor
component may have been replaced by a couple of resistors located at the
switch (it's hard to tell, but it looks like the mounting holes are wired
back to the switch).

RV1 is the red blob

The two electrolytic caps at the opposite end of the board look
suspiciously like they may be a couple of 200vdc rated caps wired in
series to provide a smoothed 350v HT supply for a switching converter
(perhaps there *are* additional surface mount components on the underside
after all but the PCB's appearance suggests otherwise).

Apart from the 6 rectifier diodes and a small glass diode (probably a
zenner)

Yes I thought it was a zener too.

I will get some better photos up and see if I can trace the circuit
and also the other PCB in the motorhead but as I only want the brush
to work would there be any harm in abandoning the Dyson PCB and
feeding it with a simple 400V rated bridge rectifier off a separate
switch?


Good luck & HTH

Yes you have been very helpful, thanks

AJH