Elecraft

PA Temp

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hank k8dd-3-2

PA Temp

How hot does your K3/100 PA run?
And how hot is safe?

I was sitting in a pileup at 90 watts and watching the PA Temp - it got up to around 41 or 42 C (about 100 F) so I turned the fan up a notch or two and it cooled right back down to around 20 C (70 F).

73 Hank K8DD

--
'Never argue with an idiot. They drag you down to their
level then beat you with experience.' -anon
--

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Don Wilhelm-4

Re: PA Temp

Hank,

I don't know how hot is safe for the K3 PA devices, but I would believe
your 42 deg C is OK.

I am going to go out on a limb and make some assumptions - that the PA
transistors are operating at 65% efficiency, that they are rated for the
normal commercial operating temperature of 125 deg C and that the
thermal resistance to the heat sink is 1 deg C per watt. If those
assumptions are correct, operating at 100 watts would mean that 54 watts
is being turned into heat at the junction, and for that power the case
temperature should not be allowed to rise above 71 deg C.

If anyone has more specific data, please correct me.

73,
Don W3FPR

hank k8dd wrote:
> How hot does your K3/100 PA run?
> And how hot is safe?
>
> I was sitting in a pileup at 90 watts and watching the PA Temp - it got up to around 41 or 42 C (about 100 F) so I turned the fan up a notch or two and it cooled right back down to around 20 C (70 F).
>
> 73 Hank K8DD
>
>
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Julian, G4ILO

Re: PA Temp

In reply to this post by hank k8dd-3-2

hank k8dd-3 wrote

I was sitting in a pileup at 90 watts and watching the PA Temp - it got up to around 41 or 42 C (about 100 F) so I turned the fan up a notch or two and it cooled right back down to around 20 C (70 F).

How did you turn up the fan? I assumed that the K3 would speed up the fan by itself when the temperature rose above thresholds defined in the firmware.

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

Eric Swartz - WA6HHQ

Re: PA Temp

Administrator

In reply to this post by hank k8dd-3-2

We will let the heatsink get up to 85C before dropping the KPA3
off-line, that still has plenty of safety margin for the transistors.

40-42C is actually on the cool side for heavy usage. But it never hurts
to keep it cool if you don't mind the added fan noise. Fortunately the
K3's dual fans are pretty quiet even at the higher speeds.

73, Eric WA6HHQ

hank k8dd wrote:
> How hot does your K3/100 PA run?
> And how hot is safe?
>
> I was sitting in a pileup at 90 watts and watching the PA Temp - it got up to around 41 or 42 C (about 100 F) so I turned the fan up a notch or two and it cooled right back down to around 20 C (70 F).
>
>
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Mike Harris-9

Re: PA Temp

In reply to this post by hank k8dd-3-2

Hi,

Not sure if the question was answered.

To turn the fans on manually: CONFIG > KPA3: VFO "A" from "PA nor" to Fn
1 through Fn 4

The setting sticks when you come out of CONFIG and through a power ON/OFF
cycle.

Regards,

Mike VP8NO

----- Original Message -----
From: "hank k8dd" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Wednesday, June 04, 2008 9:36 AM
Subject: [Elecraft] PA Temp

| How hot does your K3/100 PA run?
| And how hot is safe?
|
| I was sitting in a pileup at 90 watts and watching the PA Temp - it got
up to around 41 or 42 C (about 100 F) so I turned the fan up a notch or
two and it cooled right back down to around 20 C (70 F).
|
| 73 Hank K8DD
|
| --
| 'Never argue with an idiot. They drag you down to their
| level then beat you with experience.' -anon
| --
|
|
|
|
| _______________________________________________
| Elecraft mailing list
| Post to: [hidden email]
| You must be a subscriber to post to the list.
| Subscriber Info (Addr. Change, sub, unsub etc.):
| http://mailman.qth.net/mailman/listinfo/elecraft
|
| Help: http://mailman.qth.net/subscribers.htm
| Elecraft web page: http://www.elecraft.com

--------------------------------------------------------------------------------

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hank k8dd-3-2

Re: [K3] PA Temp

In reply to this post by Julian, G4ILO

--- G4ILO <[hidden email]> wrote:

>
>
> hank k8dd-3 wrote:
> >
> > I was sitting in a pileup at 90 watts and watching
> the PA Temp - it got up
> > to around 41 or 42 C (about 100 F) so I turned the
> fan up a notch or two
> > and it cooled right back down to around 20 C (70
> F).
> >
> How did you turn up the fan? I assumed that the K3
> would speed up the fan by
> itself when the temperature rose above thresholds
> defined in the firmware.

The fans will increase speed when the PA gets hot, but
while I was sitting there at 90 or 100 watts, pressing
the function key to send my call over and over, I
checked the PA temp and watched it rise, so it got me
wondering!

I'm not at home at the moment, but I think I went to
CONFIG:PA nor When you turn the VFO B knob you can
step through the fan speeds. I had to turn the volume
down and you could just barely hear the fan speed come
up. And you could see the PA temp come down real
fast.

The main reason I was wondering is because on one of
my K2/100's you can definitely tell that the KPA-100
has been run very hot by looking at the solder pads.

Never did work the XE2 on 6 M CW!

73 Hank K8DD

--
'Never argue with an idiot. They drag you down to their
level then beat you with experience.' -anon
--

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Dennis McAlpine

RE: [K3] PA Temp

Hank,

I had exactly the same thing happen to me in WPX as I pushed F1. In my case
the fan never went on though but the temp leveled off at about 47C.
However, in my case, the power shutdown went in and, on 40m, the xcvr seemed
to get hung up without any receive antenna when the transmission stopped.
Did you experience either of these?

73,

Dennis, K2SX

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of hank k8dd
Sent: Wednesday, June 04, 2008 4:43 PM
To: G4ILO
Cc: Elecraft Reflector
Subject: Re: [Elecraft] [K3] PA Temp

--- G4ILO <[hidden email]> wrote:

David Woolley (E.L)

Re: [K3] PA Temp

In reply to this post by hank k8dd-3-2

hank k8dd wrote:

> The main reason I was wondering is because on one of
> my K2/100's you can definitely tell that the KPA-100
> has been run very hot by looking at the solder pads.
>
Are you talking about some sort of oxidation effect. If the solder has
actually softened, you have exceeded the absolute maximum storage
temperature outside the device by some 33 degrees C and must have
exceeded the absolute maximum storage temperature inside the device by
even more. As pointed out elsewhere, nowadays commercial specification
devices are rated for an absolute maximum internal temperature, when
operating, that is 25 degrees lower that that. (Tin lead solder softens
at 183 degrees, absolute maximum storage temperature is 150 degrees and
absolute maximum operating junction temperature is 125 degrees.

Alternatively, you had a bad solder joint and the joint has heated up
locally.

--
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
that is no longer good advice, as archive address hiding may not work.
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