Sky question? Can anyone advise?

Paul Martin wrote:
In article ,
Bill Wright wrote:

"Usenet" wrote in message
...
Paul Woodsford wrote:
Common Power Supply fault with the Grundig causes similar problems. See

http://www.satcure.co.uk/accs/page12.htm

Strangely, my Grundig in the motorhome works fine from the mains, but
exhibits this fault when working from the inverter.

That's because most inverters provide only a very rough approximation
to a sine wave which looks a bit like the ASCII art below. Some
switch-mode power supplies cope with this waveform, some don't.


+---+ +---+
| | | |
-+ +---+ +---+ +---+ +--
| | | |
+---+ +---+

Put this through a transformer and you have a waveform with overshoots
and ringing on every transition.

PS. It was such an inverter that killed a Panasonic RFD1 DAB radio.
Their internal DC to DC converter is known to be marginal, and a few
uses of the inverter stopped the bugger working. I've not got round to
taking it to bits yet to see whether it's just the DC/DC that's died or
whether it's fried some other chips, too.

Once saw someone trying to simulate brown-outs by using
a lighting type dimmer switch (the ones that chop the mains
cycle at a certain point through the waveform...). The device
connected to the dimmer didn't like it much. Much smoke
from its transformer!

dom.

On 6-Mar-2007, dom wrote:

Once saw someone trying to simulate brown-outs by using
a lighting type dimmer switch (the ones that chop the mains
cycle at a certain point through the waveform...). The device
connected to the dimmer didn't like it much. Much smoke
from its transformer!

Only to be expected, some early ones (and cheap ones)
used Diacs instead of Triacs. Diacs act like rectifiers
producing pulsed partial half cycles, looking to the controlled
device like pulses of DC. Fine for things that don't mind
(commutator motors in drills, lamps and so on) not so
good for things that need very a close approximation
to a sine wave, preferably simulated in 3 or 5 steps per
1/2 cycle.