Posted by
Bob McGraw - K4TAX on
Apr 17, 2020; 7:49pm
URL: http://elecraft.85.s1.nabble.com/Electrolytic-Capacitor-failure-tp7659760p7659795.html
I have always been taught and thus have a concern when power supplies of
excessive capacity are used for any type of service. If the wiring, in
this case, between the power supply and the radio is #12 or #14 of any
length typically supplied by radio companies, should a short occur in
the power cable, it is likely the power supply will deliver full
current. That will quickly melt the insulation on the power cable and
could cause a fire before the power supply goes into current limit.
Now at the same time, each power cable could be fused at the supply to
limit the amount of current the supply can drive into the cable. I
have to say I don't like this idea as the in-line fuse adds a
significant amount of resistance and will impact the stability or degree
of regulation of the voltage at the radio under a dynamic changing load
such as SSB or CW.
All of this is no different than when one uses a battery for their
radio. In auto installations, for that reason, it is highly recommended
that a fuse or circuit breaker be located at or very near the
battery. Same applies here where the supply is capable of delivering
very high amperage. I realize power supplies of this nature have over
current protection. However, 70 amps through #14 wire will will
produce lots of heat and smoke amazingly fast.
The correct solution is not so simple in one sense of the word. The
better solution is to use properly rated supplies for the required
load. For that very reason, I have two 30 amp CCS rated supplies on my
desk. One feeds the Elecraft 100 watt transceiver while the other feeds
the Tentec Eagle 100 watt transceiver.
All of my supplies have both voltage and current meters and they are in
a position I can see them when I turn them on. With supplies which do
not have meters, when one turns them on, you never know in advance and
get what they deliver. In my case, I observe the meters BEFORE turning
on a radio. On more than one occasion this has saved a radio due to a
power supply regulation failure. Dumping 24 to 32 volts into a $3000
radios is not very pretty. Oh yes, the supplies do have OVP, Over
Voltage Protection, but I've seen this fail as well and I've repaired
several supplies where this did fail. And one doesn't know it has
failed until the voltage goes to maximum value. Its too late then to
find out the OVP circuit has failed. A meter would have prevented
radio and accessory equipment damage.
73
Bob, K4TAX
On 4/17/2020 12:28 PM,
[hidden email] wrote:
> I also use an Astron RS-70 for my K3Ss. Like you, mine was not
> purchased for this purpose. It is under my desk so the physical size
> is not an issue and I have no worries about overloading it.
>
> John KK9A
>
>
> Barry w2up at comcast.net
>
> I got a kick out of "big hulking supply," too. I have an RS-70 on my
> K3. It
> used to power a lot more stuff, but since I downsized my station, it
> loafs
> along. Definitely overkill, but it sits under the desk, out of the
> way, so
> why not? Oh yeah, my keyer's on it, too, and still doesn't get warm,
> even
> at QRQ :-)
>
> Barry W2UP
>
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