On Thu, 27 Jul 2000 18:52:01 +0100 (BST) Tony Duell
<ard_at_p850ug1.demon.co.uk> wrote:
> Much more common is that the (working) chopper transistor is never being
> turned on. And the most common cause of that is an open-circuit startup
> resistor. I've had _dozens_ of these fail over the years.
Yes, indeed. Any failure in the driver circuit to the
chopper transistor can cause it to never switch on, and
hence leave the capacitors fully charged.
I think the easiest-to-find fault I've ever seen was in an
ICL One-Per-Desk, where a transistor in the driver circuit
blew up. It made a loud bang, leaving the plastic body of
the transistor in two pieces, one having two legs, and the
other having just one.
--
John Honniball
Email: John.Honniball_at_uwe.ac.uk
University of the West of England
Received on Fri Jul 28 2000 - 07:22:33 BST