Balanced solution for KAT500 tuner?

[k6dgw]

Hmmm... I run my KPA500 @ 500W on RTTY most of the time.  120V AC.  15/10 I usually run barefoot @ 100W.  KPA500 tops out @ ~68C.  Sounds like somthing is wrong for you.
73,
Fred K6DGW


Sent from my Samsung Epic™ 4G

DGB <[hidden email]> wrote:

Am running my fairly new kpa-500 in the rtty contest. It is situated out
in the open.

it from 220v and during the run it's current runs at 10a and 64-74v. The
temp starts at 35c and as I run it slowly creeps up to 55-57c and kicks
out with the error message of "Pwr In High".

I'm only driving this with a K-3 set at about 13w to drive the amp to
350 watts. I wanted to take it easy on the amp and seems from the specs
that it should handle that. The amp. seems to be real sensitive to the
driving power of just a watt difference from the K-3. The power varies
at the amp from 250-350 watts when running and not fiddling with the K-3
power knob. I have the fan set on 1 and didn't make any difference if I
set it to 6, it still would kick out in due time, just slightly longer.
Must mention it does it whether it's into a resonant antenna or a dummy
load. The temps just slowly climb.

Anyone have a similar problem, makes it useless for rtty contesting and
running. No problems in CW contests at full bore!

73 Dwight NS9I.
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[ve3dvy]

>   The temp starts at 35c and as I run it slowly creeps up to 55-57c and kicks
> out with the error message of "Pwr In High".
does it read 35 degrees C  when the amp is cold?   and is it that hot in
your shack?    if this is the reading from a cold start I am guessing
the temp sensor is not calibrated correctly and it is reading quite
high  possibly falsely indicating a high temp when its not really that
hot.   either that or the ambient air temp is to high.
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[Jim Brown-10]

On 9/30/2012 7:53 AM, DGB wrote:
> Anyone have a similar problem, makes it useless for rtty contesting and
> running. No problems in CW contests at full bore!

Something is broken.  I get 500W out on 6M (the most difficult band)
with modes like JT65, ISCAT, and FSK441 for  48 seconds on each
transmission; typically the fan will crank higher after 35-40 seconds.  
On the lower bands I run it at 600W on JT65 and RTTY.  I also had a beta
unit for a RTTY contest weekend, with instructions to "run it with all
the lights lit."  Never any problems.

73, Jim K9YC
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['DGB']

I determined the cause was a flaw in the recent shack remodeling. I had
the K-3 and the amp. under a shelf that apparently wasn't allowing
enough air flow. Even though I had the more then the recommended
clearances for air flow, that was not enough. I put the amp. out in the
wide open Sunday morning and ran all day at 500 watts on all bands
without incident. In addition the temperature in the shack was around 75
degrees Sat. night, apparently compounding the accumulation of heat
under the shelf.

Thank you all for your responses and insight.

73 Dwight NS9I

On 9/30/2012 1:43 PM, Jim Brown wrote:

> On 9/30/2012 7:53 AM, DGB wrote:
>> Anyone have a similar problem, makes it useless for rtty contesting and
>> running. No problems in CW contests at full bore!
> Something is broken.  I get 500W out on 6M (the most difficult band)
> with modes like JT65, ISCAT, and FSK441 for  48 seconds on each
> transmission; typically the fan will crank higher after 35-40 seconds.
> On the lower bands I run it at 600W on JT65 and RTTY.  I also had a beta
> unit for a RTTY contest weekend, with instructions to "run it with all
> the lights lit."  Never any problems.
>
> 73, Jim K9YC
> ______________________________________________________________
> 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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[John K3TN]

Same experience here: K3 driving the KPA-500 on 220v to about 500w out with 23-26w drive, depending on band. When RTTY CQing, with reasonable period between CQs (like 3-4 seconds), amp temp gets up to 57-60c and the fan does its thing.

When I'm getting answers to every CQ, amp temp usually stays below 58c and lower when I'm S&Ping. If I'm fighting to keep a frequency and leave less time between CQs, amp temp will go up in high 60s but I then back off and have never gotten a HI TEMP warning.

I find it to be a FB amp for medium power RTTY work.

John K3TN