K3: Do you "Juice" your K3?

[w0mu]

In the RTTTY contest I noticed the fans changing speed now and then which is
expected.  


"A slip of the foot you may soon recover, but a slip of the tongue you may
never get over." Ben Franklin
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Bill W4ZV
Sent: Wednesday, March 11, 2009 3:45 PM
To: [hidden email]
Subject: Re: [Elecraft] K3: Do you "Juice" your K3?




Ed Muns, W0YK wrote:

>
>> During the NAQP RTTY, at one point I was calling a solid stream of
>> CQ's at 100 watts output on RTTY and not getting any replies. I was
>> watching the PA Temp, and it climbed up to 65C and looked like it
>> wanted to keep rising pretty quickly.
>> I think hi temp shutdown is at 84C. I backed off on my CQ's and used
>> the other radio for a while. I had the fan speed locked on step 4.
>> All of this was at 13.8VDC. With any kind of heavy duty usage, I
>> don't think cranking up the voltage is a good idea. A better idea is
>> to buy an AL-1500 or similar low drive amp, which will give you 1500
>> watts out with 50 watts of drive. NOW, we are talking "juice." ;)
>
> This is interesting.  I run 100 watts output on RTTY, CQing and
> working stations at a continual flow, and the fans hardly run at all.  
> The PA temperature stays down.  I wonder if there is something unique
> going on with your K3(s)?  One user found a fan wire impeding the
> blades of one of his fans and even on CW, he had the same experience
> described above.
>

That user would be me!  :-)  I strongly suspect Dave has the same problem I
did.  The longer fan wire (from the left fan viewed from the rear) was
binding the right fan.  I believe this happened when I did the 12V sense
mod.  I dropped the rear fan assembly as the directions indicated and then
replaced the assembly.  When doing this it's possible for the longer fan
wire to block the right fan and you cannot tell unless you take the top
cover off to physically inspect or test the fans to make sure both are
turning.  It's a credit to Elecraft's conservative design that heavy
operation in the ARRL DX CW with only one fan turning was not sufficient to
damage my KPA3.

Now PA TEMP seldom climbs much above 40C whereas it was resetting at ~80C
with only one fan running.  Be sure to visually check that BOTH fans are
turning.  I was fooled because it felt to my wet finger held to the rear
panel that both were turning when actually only one was.  Use the PA FN1-4
tests in the menu and make sure both are actually turning.

73,  Bill
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[Augie "Gus" Hansen]

Lance Collister wrote:
> I also am quite interested in learning what the maximum recommended supply voltage
> is for the K3.  I recall some discussion indicating that it was advisable to have
> higher voltage rather than lower, but I don't recall what the maximum was.  I have
> just ordered a 15 VDC 100A switching power supply (that can be adjusted down to
> 13.5 VDC) with the intent of running one or more solid state amps on it.  If the
> K3 can safely be used on this power supply, I would like to consolidate supplies
> and also use it to power the K3.  VY 73, Lance
>  

A word of caution is in order. SGC advises against the use of switching
supplies for their SG-500 SmartPowerCube amplifier. The recommended
supply is a stout battery with a charger to keep it topped off, or a
beefy linear supply. And I believe running the rig and amp on the same
supply could be problematic if the regulation is not really good at
handling transients.

I occasionally use my K3 with the SG-500 and use separate power supplies
for the rig and amp: An Astron RS-35M for the K3 and the SGC PS-50 for
the amp. A pair of PS-50s is recommend for high duty cycle modes.

73,
Gus Hansen
KB0YH

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[Dave Hachadorian]

Earlier today, I remarked that one of my K3's was running
warm in the NAQP RTTY after an extended number of RTTY CQ's.
Tonight I did a little experiment - key down at 100 watts
for four minutes while noting PA Temp and fan speed. It
turns out that there really is no problem. Both K3's behaved
identically and both leveled off at PA Temp = 64C after
about 3 minutes. For the record, here are the results (best
viewed with Courier font):

Time   Temp  Fan
0:00    26C   0
0:26    37    1
0:44    41    2
1:19    50    3
1:45    55    4
2:40    60    4
2:50    62    4
3:15    64    4
4:00    64    4

Room temp was 77F.

Dave Hachadorian, K6LL
Yuma, AZ

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[hf4me]

Those are my thoughts also.  Follows is my way of isolating the "shock" of
an 80 amp audio modulated load from my K3 input power supply.

I do run my radio bench with a 70 amp linear Astron supply BUT I have a
seperate Power supply buss(pair) and a battery buss(pair)(plus a seperate
ground buss bar).  The two busses are connected to each other by a knife
style disconnect from an air-conditioner cutoff (new and removed from box
and mounted under bench) BUT there is 25 feet or wire involved and the spare
wire (about 20 of the 25 feet) is coiled up as a sort of (wimpy) inductor.
BTW, the 4 buss bars (2 bar pairs) are 1/4 by 1 inch aluminum and the ground
buss is 1/4 by 1 inch copper mounted on the upper back of my bench.  The
wire is long and is 14 ga on purpose to add resistance to partially isolate
the "shock" of the 80 amp requirement (during audio peaks) of the ALS500
solid state amplifier.  The amp is wired to the battery buss with 3 pairs of
12 ga wires (14 inches) and the battery buss is wired to the battery also
with 3 pairs of 12 ga wires (12 inches).  The battery is two LARGE
automotive batteries (one stolen for my truck recently not yet replaced).
(Flame on about gasses if you wish, I'm not listening)  I don't want that
shock on the power supply AND I don't want my K3 to have to try to operate
properly on that kind of voltage that must be very noisy (and it matters not
if the power goes out, I keep on operating).

The battery buss (and batteries) is held up in non-use times by a battery
maintenance charger (of no use during operation).  Not one of the $7 ones
that are useless on this size battery (if any), these are about $30 and are
larger and "intelligent" and monitor and only add charge as needed.

73, de Jim KG0KP

----- Original Message -----
From: "Dave Hachadorian" <[hidden email]>
To: "Elecraft reflector" <[hidden email]>
Sent: Wednesday, March 11, 2009 11:53 PM
Subject: Re: [Elecraft] K3: Do you "Juice" your K3?

> Earlier today, I remarked that one of my K3's was running
> warm in the NAQP RTTY after an extended number of RTTY CQ's.
> Tonight I did a little experiment - key down at 100 watts
> for four minutes while noting PA Temp and fan speed. It
> turns out that there really is no problem. Both K3's behaved
> identically and both leveled off at PA Temp = 64C after
> about 3 minutes. For the record, here are the results (best
> viewed with Courier font):
>
> Time   Temp  Fan
> 0:00    26C   0
> 0:26    37    1
> 0:44    41    2
> 1:19    50    3
> 1:45    55    4
> 2:40    60    4
> 2:50    62    4
> 3:15    64    4
> 4:00    64    4
>
> Room temp was 77F.
>
> Dave Hachadorian, K6LL
> Yuma, AZ
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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