"Arfa Daily" wrote in
:


"pfm" wrote in message
.
..
I continue to try and repair a CRT TV. The set's main SMPS is a
discrete, self oscillating design. The set powers up for a few
seconds and then shuts down; I think the Micon controller chip
releases the AC relay. The B+ open circuit voltage is 139V (ie
disconnected from the horizontal output). When a 60W bulb is
substituted as a load for the 'horizontal', the voltage is zero, not
a glimmer from the bulb. How can the B+ power up the set, albeit
briefly, but not light the bulb? Is there a problem with a simple
resistive load? Is it possible that the horizontal stage is essential
to the operation of the SMPS? Any thoughts please?

BobH

A light bulb is not really a 'simple resistive load'. When the
filament is cold, its resistance is much lower than when it's up to
temperature, so it might just be that when the power supply tries to
drive it from cold, it just represents a bit too much of a load,
causing the PSU to trip back to standby.

Arfa




problem is probably bad electrolytic caps.

--
Jim Yanik
jyanik
at
localnet
dot com