That sounds like a good thing to do. An improvement you can make to the
standard Drake power supply is to connect .01uF caps across each of the
diodes. Also, bypass each leg of the power transformer secondary to ground
witha 1uF NP cap. This removes that "flourescent ballast" type of buzzing
hash that you may hear on frequencies below 700kHz. If you have the later
unit that tunes down to 100kHz (which I wish I had), expect much lower noise
performance down there.
Pete
"starman" wrote in message
...
Pete KE9OA wrote:
Hi folks,
I decided to check out my SW8 a little bit more. I measured
the
wall wart voltage, and it measured 9.6VDC, so it seemed to be within
limits.
Just for the heck of it, I checked the ripple voltage with a scope. 4.6V
p-p
of ripple!
I opened up the supply, and discovered that the filter cap had exploded.
Just for the record, this isn't a regulated supply; it is merely a
transformer, four diodes, and a filter capacitor.
I decided to build up my own 10V supply, using a 1000uF cap and a 7810
regulator. I also decided to go with a 3-wire grounded power cord, using
single point grounding on the power supply board.
Now, all of the buzz on the low end of the MW band is gone, and the
sensitivity is much better. Also, the intermittent display backlight
problem
is gone.
Still not quite as sensitive as my other receivers, but not bad. MDS is
now
down below .1uV, which is pretty ok.
Pete
I got tired of keeping track of the wallwart for my SW8, which doesn't
fit in the Drake carry bag. The remedy was to cut open the wall wart and
install the parts in the radio. I had to move the battery holder about
an inch to one side to make room for the transformer. It was a tight
fit. I also added a receptacle on the back which accepts a standard
computer power cord. I probably have the only SW8 with an internal AC
power supply.
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