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Re: Elecraft] KXPA100 Thermal Fault

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k6dgw

Re: Elecraft] KXPA100 Thermal Fault

When I was using my K2/100 on RTTY, I stuck a muffin fan over the hottest part of the heatsink with a little square of sticky back velcro. Could run 100 watts just fine. Fan blew down.

73,
Fred K6DGW
TDY Huntington Beach CA

Bert via Elecraft <[hidden email]> wrote:

>Thanks to all who made suggestions. I will be trying one or two fans atop
>the heat sink and see how that works out in the next RTTY contest foray.
>While looking into possibilities, I checked out the web site where I got my
> "add-on" KX3 heat sink (https://proaudioeng.com/products/) and found they
>had added a new product, a power supply specifically for the KX3. Specs
>look promising. [I don't have a vested interest in the company, just pleased
>with the heat sink.]
>Again, this reflector is a great source for ideas about great products!
>73, Bert N4CW/K1IMI
>
>
>In a message dated 7/20/2014 7:18:48 P.M. Eastern Daylight Time,
>[hidden email] writes:
>
>I used my KX3/KXPA100 in the NAQP RTTY contest this weekend. The KX3 with
>added-on heat sink worked very well; however, the KXPA100 repeatedly faulted
> with HI TEMPERATURE indicated on the KX3 at full output after prolonged
>operating (lots of CQ'ing with short pause intervals). PA.X temp indicated at
> failure was around 60C...as it should. Shack temperature was around 70
>degrees F
>Yes, I know all about digital modes and full power stressing amplifiers,
>etc. What I want to know is how to mitigate this interruption yet run full
>output. To that end, I have a couple ideas: what if I mounted the amp
>vertically so the heatsink fins "drew" cooler air through themselves via
>convection? Secondly, would a couple muffin fans mounted atop the cooling fins do
>the job?
>The net of this is that I'd like to enjoy the full benefit of having a
>high-quality 100-Watt amplifier, regardless of mode or key-down time.
>
>Bert N4CW/K1IMI
>
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Mike Harris-9

Re: Elecraft] KXPA100 Thermal Fault

There will always be disagreement on this but I vote for blow when
external forced cooling. The air can be directed exactly to where it is
needed, not sucked from all over the place.

I ran my K2 overnight for days at 50W doing some Grey-line propagation
tests. Small external fan tilted at 45 degrees and blowing down onto
the heat sink in the area where the transistors were bolted. The little
screamer on the back of the KPA100 never activated.

The situation with the K3 is different, the PA heat sink is buried in
the box and the heat has to be sucked out otherwise all you would have
is a fan oven.

Regards,

Mike VP8NO

On 21/07/2014 20:37, Fred C. Jensen wrote:
> When I was using my K2/100 on RTTY, I stuck a muffin fan over the hottest part of the heatsink with a little square of sticky back velcro. Could run 100 watts just fine. Fan blew down.
>
> 73,
> Fred K6DGW
> TDY Huntington Beach CA
>
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Edward R Cole

Re: Elecraft] KXPA100 Thermal Fault

In reply to this post by k6dgw

Re: blowing air vs drawing air, the object is to increase air flow
over the heat sink (or tube if no heat sink). If one does not have a
plenum directing air over the entire heat sink surface, my bet is
with blowing. Drawing air is effective if there is a plenum
confining the air flow over the heat sink surface.

I you are cooling a tube with fins like some of the 3CX or 4CX types
then you need the extra force of a blower due to the high air
resistance (back pressure) thru the fins. Example a 8877
(3CX1500A). I have both a blower and 7-inch radial exhaust fan on
that amp. Exhaust fan lowers back pressure that the blower works into.

All my other amps are currently configured with fans that blow down
onto the heat sink. I will be installing five fans on a 6m Harris TV
amplifier (1100w with 16 transistors) that draws air. That is needed
as air is drawn thru several holes from the input side of the amp for
cooling the input components by pulling air into the output side.

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

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k6dgw

Re: Elecraft] KXPA100 Thermal Fault

In reply to this post by k6dgw

Mine was a brushless DC fsn from an old computer. Quiet running on 12V. One anomally ... on 15 (only), with beam pointed over shack & 1KW, transmitting slowed it down. Any other direction was fine

73,
Fred K6DGW
TDY Huntington Beach CA

Don Wilhelm <[hidden email]> wrote:

>Salvage a 12 volt muffin fan from a defunct computer and put a resistor
>in series with it to slow it down. Almost whisper quiet, but it can
>substantially increase the air flow over the heatsink and keep it cool.
>Cost, almost nothing. But put a shield over it to keep fingers out of
>the blades.
>
>73,
>Don W3FPR
>
>On 7/22/2014 6:18 PM, Bob N3MNT wrote:
>> This looks like a a relatively inexpensive solution to the temp controlled
>> fan idea. They seem to have a reputation for being quiet and reliable.
>> http://sitesearch.outletpc.com/search?page=1&query=Gelid+FN-TX12-15+Silent+++ON1266+++++++++1+++9.98++Warranty+%3D+30-Day+Warranty+Included+12+TC+120mm+3pin+1500RPM+++++++++++++++++++++++++++%28%2B0.00%29+Temp+Control+Case+Fan&I1.x=55&I1.y=3
>>
>>
>>
>
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