12 May
1998
12 May
'98
3:39 p.m.
3) The fuse is fine, but the PSU won't start up. This is suprisingly
common (I've had it twice in the last month). Most small SMPSUs run the
control circuitry off one of the transformer outputs, which leads to a
bootstrap problem (the PSU can't run without the control circuit, but the
control circuit can't work without the PSU running). The solution is a
small circuit to give the control circuit enough power to start. In a lot
of cases this takes the form of a high-value resistor chain from the HT+
(400V DC) line to the chopper control circuitry. And for some reason this
resistor open-circuits. It's worth checking all high-value resistors on
the primary side.
When you've inspected the fuse, get back to us and we'll attempt to talk
you through the PSU...
-tony
Well, I checked the fuse on the P/S, and its OK. So what is the next step?
Is this something I can take to a repair shop. I know of a TV & stero shop
that has worked wonders on an old Pioneer amplifier of mine. A P/S should be
of no problem for them. I would like to attemp to fix my self, but I just
don't have that sort of time at the moment! Or can anybody recommend someone
I can send it (the power supply only) to for repair?
Cliff Boyer