Hi..
I've just recently obtained a Codan 7010 HF Linear and associated exciter and
power supply.
This was originally a complete stand alone 2-15 Mhz HF Transmitter used by our
Maritime
Authorities with 4 4CX250B's in parallel and auto tune.
Whilst cleaning the thing up for future amateur use, the power supply has
needed some caps
replaced and some new IN5408's to replace the ageing and ancient IN4007's.
The power supply is a cap input setup, but with a tuned choke on the B- return
leg, which is
held down near ground by a 5.6 ohm 10w power resistor with two 680uf electro's
across it.
The voltage developed across this resistor/cap setup is used for EHT fault
detection ( too
much current). The large choke is positioned just before the return to the
bridge with three
680n polycarbonate caps across the choke to tune it to the ripple
frequency...two chokes
were specified in the parts list, one for 50hz and one for 60hz. The
polycarbonate caps have
gone to god, leaving a large charred black mess. I have managed to obtain some
metallised
polypropylene types rated at 400ac to replace them with, as the original
polycarbonates are
apparently now defunct...these originals were rated 450ac.
My question is this...is the tuned choke required, or is this just an old
design philosphy
that can be dispensed with, along with the caps ?
Any input on the above greatfully received.
Regards,
Glenn
VK4TZL
|