On Tue, 18 Oct 2011 01:47:17 +0100, "Arfa Daily"
wrote:

Across that primary, is a network comprising a 330pF 2 Kv disc ceramic cap,
and two 3 watt cement-body resistors, all in series.

1. A what frequency is the SMPS supply running?
2. Look at the xformer or inductor with a loosly coupled pickup, and
see if there is any RF or spurious oscillations happening. 330PF at
perhaps 40KHz is 12K ohms, which isn't going to conduct enough current
to get the 150 ohm resistor even slightly warm. However, 330pf at
some higher RF frequency just might do the trick.
3. The design sounds like it might be belching some switching noise
back out the power line as conducted EMI/RFI. The 330pf and 150 ohm
resistor networks seem like they're there to reduce this EMI to
regulatory limits.

Hint: The most efficient switching power supply, is full of fast rise
time waveforms, and is therefore also an EMI/RFI noisy supply.

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