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K3 powers off when after several minutes of 12W carrier

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K7TV

K3 powers off when after several minutes of 12W carrier

I have been testing sustained power capabilities of wideband HF transformers
for feeding EFHW antennas. This involves running high power through HF
transformers back to back into a dummy load. When running 200W out of the
KPA500, the K3 was indicating 12W, and I think that means the 100W PA was
not operating. After a few minutes the K3 totally shut down. This had
nothing to do with the transformers under test; I get the same result when
running the KPA500 at 200W directly into the dummy load. After restart the
K3 shows no sign of problem unless the 200W endurance test is run again.
Then I increased power just a little bit so that the 100W stage kicked in. I
got 300W out of the KPA500, and now the K3 keeps going without shutting
down. I can see how 12W may be a bit much for the driver stage, but if so,
shouldn't the 100W stage kick in sooner? Also, I expected the K3/KPA500
combo to be able to produce any power level I wanted within its range. What
I see is that when the 100W stage kicks in, the output (as seen on an analog
meter) makes a big jump so that certain power levels cannot be achieved.

Thanks,
Erik K7TV

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K7TV

Re: K3 powers off when after several minutes of 12W carrier

Same result if the K3 is run at 12W without the KPA500. This is a K3 I
bought used; I guess I may have forgotten to check the power calibrations on
it. Will try that next.
73,
Erik K7TV

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Erik Basilier
Sent: Tuesday, March 27, 2018 9:42 PM
To: [hidden email]
Subject: [Elecraft] K3 powers off when after several minutes of 12W carrier

I have been testing sustained power capabilities of wideband HF transformers
for feeding EFHW antennas. This involves running high power through HF
transformers back to back into a dummy load. When running 200W out of the
KPA500, the K3 was indicating 12W, and I think that means the 100W PA was
not operating. After a few minutes the K3 totally shut down. This had
nothing to do with the transformers under test; I get the same result when
running the KPA500 at 200W directly into the dummy load. After restart the
K3 shows no sign of problem unless the 200W endurance test is run again.
Then I increased power just a little bit so that the 100W stage kicked in. I
got 300W out of the KPA500, and now the K3 keeps going without shutting
down. I can see how 12W may be a bit much for the driver stage, but if so,
shouldn't the 100W stage kick in sooner? Also, I expected the K3/KPA500
combo to be able to produce any power level I wanted within its range. What
I see is that when the 100W stage kicks in, the output (as seen on an analog
meter) makes a big jump so that certain power levels cannot be achieved.

Thanks,
Erik K7TV

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jh3sif

Re: K3 powers off when after several minutes of 12W carrier

My friend had similar problem. It cause was that LPA was not tightly attached to K3 bottom cover.
After retighten the screw attaching the LPA to bottom cover, the problem was solved.
I hope this helps.

73 de JH3SIF, Keith

> 2018/03/28 13:51、Erik Basilier <[hidden email]>のメール:
>
> Same result if the K3 is run at 12W without the KPA500. This is a K3 I
> bought used; I guess I may have forgotten to check the power calibrations on
> it. Will try that next.
> 73,
> Erik K7TV
>
> -----Original Message-----
> From: [hidden email] <[hidden email]> On
> Behalf Of Erik Basilier
> Sent: Tuesday, March 27, 2018 9:42 PM
> To: [hidden email]
> Subject: [Elecraft] K3 powers off when after several minutes of 12W carrier
>
> I have been testing sustained power capabilities of wideband HF transformers
> for feeding EFHW antennas. This involves running high power through HF
> transformers back to back into a dummy load. When running 200W out of the
> KPA500, the K3 was indicating 12W, and I think that means the 100W PA was
> not operating. After a few minutes the K3 totally shut down. This had
> nothing to do with the transformers under test; I get the same result when
> running the KPA500 at 200W directly into the dummy load. After restart the
> K3 shows no sign of problem unless the 200W endurance test is run again.
> Then I increased power just a little bit so that the 100W stage kicked in. I
> got 300W out of the KPA500, and now the K3 keeps going without shutting
> down. I can see how 12W may be a bit much for the driver stage, but if so,
> shouldn't the 100W stage kick in sooner? Also, I expected the K3/KPA500
> combo to be able to produce any power level I wanted within its range. What
> I see is that when the 100W stage kicks in, the output (as seen on an analog
> meter) makes a big jump so that certain power levels cannot be achieved.
>
> Thanks,
> Erik K7TV
>
> ______________________________________________________________
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Brian Hunt

Re: K3 powers off when after several minutes of 12W carrier

In reply to this post by K7TV

For folks who run lots of high duty cycle modes, Elecraft is now recommending 'thermal pads' between the LPA transistors and the bottom cover. I found this out when I was doing some mods to my 10yo K3 and the instructions said to install them and I didn't have 'em. You can get them from Elecraft, not expensive.

73,
Brian, K0DTJ
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ke9uw

Re: K3 powers off when after several minutes of 12W carrier

So there was a time early on for the K3 when the pads were not installed? I looked at my 2010 assembly instructions and they required them. So I must have put them in.

Chuck Jack
KE9UW

Sent from my iPhone, cjack

> On Mar 28, 2018, at 6:24 PM, Brian Hunt <[hidden email]> wrote:
>
> For folks who run lots of high duty cycle modes, Elecraft is now recommending 'thermal pads' between the LPA transistors and the bottom cover. I found this out when I was doing some mods to my 10yo K3 and the instructions said to install them and I didn't have 'em. You can get them from Elecraft, not expensive.
>
> 73,
> Brian, K0DTJ
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Chuck, KE9UW

Rose

Re: K3 powers off when after several minutes of 12W carrier

Any chance of model confusion between K2 and K3? I recall adding them to
my K2 ... a case of having to hold my tongue just so in order to hold them
and their hardware in place. Not a place for fat fingers!

73!

K0PP

On Wed, Mar 28, 2018, 17:36 hawley, charles j jr <[hidden email]>
wrote:

> So there was a time early on for the K3 when the pads were not installed?
> I looked at my 2010 assembly instructions and they required them. So I must
> have put them in.
>
> Chuck Jack
> KE9UW
>
> Sent from my iPhone, cjack
>
> > On Mar 28, 2018, at 6:24 PM, Brian Hunt <[hidden email]> wrote:
> >
> > For folks who run lots of high duty cycle modes, Elecraft is now
> recommending 'thermal pads' between the LPA transistors and the bottom
> cover. I found this out when I was doing some mods to my 10yo K3 and the
> instructions said to install them and I didn't have 'em. You can get them
> from Elecraft, not expensive.
> >
> > 73,
> > Brian, K0DTJ
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
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> > Message delivered to [hidden email]
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markmusick

Re: K3 powers off when after several minutes of 12W carrier

In reply to this post by ke9uw

When I built K3 serial #3505 in September of 2009, the kit had thermal pads
for the LPA transistors.

Mark, WB9CIF

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of hawley, charles j jr
Sent: Wednesday, March 28, 2018 11:34 PM
To: Brian Hunt <[hidden email]>
Cc: [hidden email]
Subject: Re: [Elecraft] K3 powers off when after several minutes of 12W
carrier

So there was a time early on for the K3 when the pads were not installed? I
looked at my 2010 assembly instructions and they required them. So I must
have put them in.

Chuck Jack
KE9UW

Sent from my iPhone, cjack

> On Mar 28, 2018, at 6:24 PM, Brian Hunt <[hidden email]> wrote:
>
> For folks who run lots of high duty cycle modes, Elecraft is now
recommending 'thermal pads' between the LPA transistors and the bottom
cover. I found this out when I was doing some mods to my 10yo K3 and the
instructions said to install them and I didn't have 'em. You can get them
from Elecraft, not expensive.

>
> 73,
> Brian, K0DTJ
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
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> list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]

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Brian Hunt

Re: K3 powers off when after several minutes of 12W carrier

My K3 is #4113 factory assembled and delivered in April 2010. I'm pretty sure the bottom cover had never been off when I did the update mods a couple months ago. That's when I asked Elecraft support about it and I assumed it had been added to later #s. I've never had any issues but run mostly CW at either 5 watts or 100 watts.
73,
Brian, K0DTJ

> On Mar 28, 2018, at 18:02, Mark E. Musick <[hidden email]> wrote:
>
> When I built K3 serial #3505 in September of 2009, the kit had thermal pads
> for the LPA transistors.
>
> Mark, WB9CIF
>

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K7TV

Re: K3 powers off when after several minutes of 12W carrier

In reply to this post by K7TV

Brian, thanks for that tip. I bought this K3 used, so I didn't put it
together. Will have to inspect to find out if pads are installed. The serial
# 2241 suggests to me that the pads might indeed be missing.

Recalibrating the wattmeter plus TX gain did not eliminate the problem of
the K3 powering down, and there is still a gap in obtainable output powers.
After recalibration (without the KPA500) the powers not obtainable on 80m
was anything between 12 and 16. I get the impression that this is normal
behavior. Not a problem for normal hamming, and only a minor annoyance when
using the rig as a variable power test instrument. Running the same
endurance test with power setting 12W on 20m did not seem to lead to the rig
shutting down, and the range of unobtainable output powers is actually
between 9 and 12. I attribute this to variations in wattmeter sensitivities
between 80m and 20m. Of course the wattmeter calibration is performed only
on the 20m band.

As I performed the wattmeter calibration today I ran into a complication
that I don't remember from last time I did this (over a year ago). Following
the manual instructions I set the power to 5.0W. (I did this using the power
knob; first I misread it to mean tweak the power setting to obtain a 5W
indication on the external wattmeter. The manual really should not be
ambiguous on this). I brought up the CONFIG:WMTR LP display as instructed. I
then held TUNE to start transmission, and was ready to adjust the main
tuning knob to get 5W on the external meter. However, the transmission did
not utilize the 5W PWR setting. Instead it used the TUN PWR setting, which
happened to be very different. To complete the procedure I had to go back
and adjust TUN PWR to 5W. I must be missing something here...

73,
Erik K7TV

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Brian Hunt
Sent: Wednesday, March 28, 2018 4:24 PM
To: [hidden email]
Subject: Re: [Elecraft] K3 powers off when after several minutes of 12W
carrier

For folks who run lots of high duty cycle modes, Elecraft is now
recommending 'thermal pads' between the LPA transistors and the bottom
cover. I found this out when I was doing some mods to my 10yo K3 and the
instructions said to install them and I didn't have 'em. You can get them
from Elecraft, not expensive.

73,
Brian, K0DTJ
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N2TK

Re: K3 powers off when after several minutes of 12W carrier

In reply to this post by Brian Hunt

Anything special about the thermal pads they recommend or the placement of
the pads? Is there anything on the Elecraft site I missed on this?
Tnx
N2TK, Tony

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Brian Hunt
Sent: Wednesday, March 28, 2018 7:24 PM
To: [hidden email]
Subject: Re: [Elecraft] K3 powers off when after several minutes of 12W
carrier

For folks who run lots of high duty cycle modes, Elecraft is now
recommending 'thermal pads' between the LPA transistors and the bottom
cover. I found this out when I was doing some mods to my 10yo K3 and the
instructions said to install them and I didn't have 'em. You can get them
from Elecraft, not expensive.

73,
Brian, K0DTJ
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Don Wilhelm

Re: K3 powers off when after several minutes of 12W carrier

Tony,

Unless you have a very old K3, the thermal pads should already be in
place. Remove the rear bottom panel to see if they are present.

The thermal conductivity of the pads is the important parameter. Get
the correct thermal pads from Elecraft, they are effective p/n E700002 -
Adhesive Thermal pads TO220 size. They are easy to apply.

73,
Don W3FPR

On 3/29/2018 8:20 AM, N2TK, Tony wrote:
> Anything special about the thermal pads they recommend or the placement of
> the pads? Is there anything on the Elecraft site I missed on this?
> Tnx
> N2TK, Tony
>
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Barry Baines

Re: K3 powers off when after several minutes of 12W carrier

Don:

I have the K3-KPA500-KAT500 purchased in August 2014. Using the Y-Box offered by Bob Wilson, N6TV which he configured me, I have the K3 attached to Antenna Genius (AG) Radio Port A with BCD and it works well. Similarly, I’m using the USB interface on the Flex-6700 to provide BCD to the AG on Radio Port B and it works well.

The key advantage of this approach is that I primarily operate remote. Using BCD for both devices means I don’t have to run the AG app on a PC to match the antenna port of either radio upon startup of each radio, ensuring that the proper antenna for the desired operating band is selected (Tribander or Offset Half-wave wire). Of course, if I want to select a second antenna port for the desired band (such as a dummy load), I can still use the AG app to make the change.

One thing to point out is that BCD configuration for 160M is different between the K3 and AG, so it isn’t possible to select an antenna defined as 160M. The DB-15 pin assignments of the AG and K3 ACC lines for BCD logic also differs. As I recall, there is also a voltage level difference between Elecraft and AG when using BCD and Bob had to build a circuit within the Y-Box setup to compensate for this. Bob posted an e-mail to this list on 15 SEP 17 describing how he configured the Y-Box to work with AG and still allow the KPA-500, KAT-500 to function as intended.

My recommendation for those with a K3 who want to have a BCD connection to an Antenna Genius should consider Bob’s Y-Box configuration for AG as an effective interface between the two devices.

FWIW,

Barry Baines, WD4ASW
Keller, TX

> On Mar 29, 2018, at 12:06 PM, Don Wilhelm <[hidden email]> wrote:
>
> Tony,
>
> Unless you have a very old K3, the thermal pads should already be in place. Remove the rear bottom panel to see if they are present.
>
> The thermal conductivity of the pads is the important parameter. Get the correct thermal pads from Elecraft, they are effective p/n E700002 - Adhesive Thermal pads TO220 size. They are easy to apply.
>
> 73,
> Don W3FPR
>
> On 3/29/2018 8:20 AM, N2TK, Tony wrote:
>> Anything special about the thermal pads they recommend or the placement of
>> the pads? Is there anything on the Elecraft site I missed on this?
>> Tnx
>> N2TK, Tony
> ______________________________________________________________
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