[Elecraft] Electrolytic Capacitor failure

[Bob McGraw K4TAX]

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, john at kk9a.com 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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