Gary, you may be trying to chop the cabbage a bit finer than necessary. If
you take a close look at the input power circuit for the K3 you will see the
power pole voltage is the voltage seen by the circuit breaker and the 100W
amp. The voltage measured by the K3 is after the polyfuse (12A) which feeds
the receiver, fan, and P3 (via the power socket). The fuse drops a little
voltage which is why there is a slight difference in readings. The higher
voltage does not affect the receiver because there are several series
regulators (9V & 5V) that derive their supply from 12A (post fuse 12V). In
the end it is not that critical except the 100W amp will run cleaner and
cooler as the voltage goes up. Also your external power supply, if linear,
will also run slightly cooler as the output voltage is adjusted upwards.
There will be negligible temperature drop on switching supplies. Of course
there are limits as to how high you can raise the input voltage. Read your
K3 input power specification for this value.
From: [hidden email] [mailto:[hidden email]] On Behalf Of Gary K9GS
Sent: Tuesday, April 16, 2013 8:56 PM
To: [hidden email] Subject: Re: [Elecraft] K3 power supply recommendations
I have a question on adjusting the voltage a bit higher for use with the K3.
I was thinking of 14.5 V, as others have mentioned, and adjusting voltage on
I have an accurate voltmeter.
Should I set the voltage with the voltmeter measuring at the DC input to the
K3 (at the power pole into the radio) or should I use the internal voltmeter
in the K3?
On 4/16/2013 9:05 AM, Mike Reublin wrote:
> I've used an Astron RS-35M very happily for years. Had to turn it up a tad
for the K3.
> Tip: The voltage adjustment is on the under side of the board......
> 73, Mike NF4L
> On Apr 16, 2013, at 8:03 AM, Tom Branton <[hidden email]>
>> The K3 in question is a K3/100. Thanks,
>> On Apr 16, 2013, at 6:26 AM, "Tom Branton" <[hidden email]>
>>> Good morning everyone ,
>>> I think I have found a very nicely maintained and equipped K3 to
purchase. Any purchase recommendations as to a well constructed and trouble
free power supply?
Another vote for the RM-35. I have had mine for over 30
years. Not an issue.
Note however that Astron over specs their power supplies.
They claim that the RS-35 will do 25A continuous. It will
not. It gets too darn hot. Given the heatsink, it should
do about 20 continuous. This is with static air cooling,
no forced air.
That being said, the RS-35 powered all 12 volt equipment in
my shack including the 120W HF radio, TNC, 50W 2m radio for
packet and dx cluster, and any othe vhf or other radios
that I wanted on. I have seen the ammeter move past 33A
when the SSB voice peaks combine with the transmit cycle of
the packet radio, with no issues.
On Tue, 16 Apr 2013 21:05:18 -0700 (PDT)
Wes Stewart <[hidden email]> wrote:
> Use your meter. BTW, I second, third, fourth... the
> recommendation of the RM-35. Mine has been converted to
> a "smart charger" that keeps a 95AH AGM battery charged,
> but before that was used normally without incident.
> --- On Tue, 4/16/13, Gary K9GS <[hidden email]>
> From: Gary K9GS <[hidden email]>
> Subject: Re: [Elecraft] K3 power supply recommendations
> To: [hidden email] > Date: Tuesday, April 16, 2013, 9:56 PM
> I have a question on adjusting the voltage a bit higher
> for use with the
> K3. I was thinking of 14.5 V, as others have mentioned,
> and adjusting
> voltage on receive.
> I have an accurate voltmeter.
> Should I set the voltage with the voltmeter measuring at
> the DC input to
> the K3 (at the power pole into the radio) or should I use
> the internal
> voltmeter in the K3?