On Fri, 21 Oct 2016 11:31:26 +0100, wrote:

I inherited this a year ago and it has been a good vacuum cleaner with
it's own little electric motor to power the brush head.

It has stopped rotating the motorhead without warning and a red LED is
glowing when power is switched to the head.

I have stripped the head and it uses a Domel 230VDC motor via a PCB
which has the LED. This motor rotates slowly when 12VDC is applied.

The two leads coming to the head measure 90VDC on a moving coil meter.

I'm thinking the head and PCB are probably OK but some diodes have
gone open circuit in the power supply.

Any thoughts?

https://www.dyson.co.uk/support/dc05/dc05-motorhead

(Don't just Google Motorhead or you might get a completely different
answer!) I would give them a ring - nothing to lose. There is a good
Dyson repairer near me and I am sure there must be many more. Maybe
they could cannibalise another machine?