"Dave W" wrote in message
...
"Arfa Daily" wrote:

Hmmm. Now it gets a whole lot more complicated. With a mains supply
between
about 60v and 160v, it works. It will light a lamp, and support
considerable
amounts of current. However, as you go above that voltage, you can watch
on
the 'scope, the activity around the switching devices progressively die,
until it stops altogether. I think that the next thing I am going to do is
look for the 'potted down' supply to that little sub board, and see if it
ever stabilizes at any figure, or just keeps going up and up. I've spotted
a
fairly meaty 220k resistor straight off the bridge, heading in that
direction, so I guess that might be a good place to start.

Arfa

Might this thing be for US mains? Also, there used to be converters
which automatically switched between US and UK mains by using two
SCR's and two diodes in a full-wave bridge arrangement for 120V, and
switching off the SCR's so the diodes acted as a half-wave bridge for
240V.

Dave W



No, it's a genuine UK mains only input. It's front end is just a bridge
across the mains supply, not even the sophistication of a filter cap, let
alone any kind of auto voltage sensing. Anyways, I've sorted the problem
now - see reply to meow2222

Arfa