Just to add to what Arfa said, the supply to the PWM chip often starts
with a simple resistor feed from the +170V rectfied mains voltage, and
is then augmented by a regenerated supply from a tap on the switchmode
transformer. If this is the case, then there will be a small
electrolytic filter capacitor (~10uF) that often develops high ESR.

- Franc Zabkar


Hi Franc,

I found the 10uf cap you mention and measured the ESR. It was very
high (around 50), so i replaced it with another cap i had around. it
is not a low esr cap and only an 85 deg one, but figured it would be
ok for testing. it measures about 4.5 on the esr meter which is still
a little high (should be closer to 2). I still get the same result
when its hooked up.

-R