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KPA1500 Thermal problems

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Jim AB3CV

KPA1500 Thermal problems

I participated in the WAE RTTY contest this past weekend and was having
problems with thermal tripping.

I have resonant antennas for 80, 40 and 20m and had SWR between 1:1 and
1.2:1, power nominally set between 1400-1500w.

I found that I couldn't repeatedly CQ without temperature creeping up so I
paused to around 50% duty cycle to stop that.

However when sending QTC which amount to about 200 characters the
temperature would rapidly increase and eventually thermal trip.

I took several actions to try to compensate:

I opened the shack windows and bundled up. Shack then stayed at 60f or
below.
I immediately manually cranked the fan speed to max (5) when started to
send QTCs.
I rode the drive power downward as the power increased to stay below the
trip point of 105c.

Upon taking all these actions I was able to eventually send the QTC packets
but it was unnerving and unexpected.

This is a low serial number KPA1500 but with latest production firmware.

What have others seen?

73

jim ab3cv
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ANDY DURBIN

KPA1500 Thermal problems

"I rode the drive power downward as the power increased to stay below the trip point of 105c."

Was that intended to be "as the temperature increased"? If so, do you have any data that shows PA dissipation is lower at reduced power levels for the KPA1500? For the KPA500 PA dissipation increases as power is reduced and peaks at about half rated output.

73,
Andy, k3wyc
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Jim AB3CV

Re: KPA1500 Thermal problems

In reply to this post by Jim AB3CV

" I rode the drive power downward as the power increased to stay below the
trip point of 105c."

Should have been "as the temperature increased"

jim ab3cv

On Mon, Nov 11, 2019 at 9:03 AM Jim Miller <[hidden email]> wrote:

> I participated in the WAE RTTY contest this past weekend and was having
> problems with thermal tripping.
>
> I have resonant antennas for 80, 40 and 20m and had SWR between 1:1 and
> 1.2:1, power nominally set between 1400-1500w.
>
> I found that I couldn't repeatedly CQ without temperature creeping up so I
> paused to around 50% duty cycle to stop that.
>
> However when sending QTC which amount to about 200 characters the
> temperature would rapidly increase and eventually thermal trip.
>
> I took several actions to try to compensate:
>
> I opened the shack windows and bundled up. Shack then stayed at 60f or
> below.
> I immediately manually cranked the fan speed to max (5) when started to
> send QTCs.
> I rode the drive power downward as the power increased to stay below the
> trip point of 105c.
>
> Upon taking all these actions I was able to eventually send the QTC
> packets but it was unnerving and unexpected.
>
> This is a low serial number KPA1500 but with latest production firmware.
>
> What have others seen?
>
> 73
>
> jim ab3cv
>

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AE4ED

Re: KPA1500 Thermal problems

What output power did that reduce too ultimately, is 105c the design temp
limit?

On Mon, Nov 11, 2019 at 8:30 AM Jim Miller <[hidden email]> wrote:

> " I rode the drive power downward as the power increased to stay below the
> trip point of 105c."
>
> Should have been "as the temperature increased"
>
> jim ab3cv
>
> On Mon, Nov 11, 2019 at 9:03 AM Jim Miller <[hidden email]> wrote:
>
> > I participated in the WAE RTTY contest this past weekend and was having
> > problems with thermal tripping.
> >
> > I have resonant antennas for 80, 40 and 20m and had SWR between 1:1 and
> > 1.2:1, power nominally set between 1400-1500w.
> >
> > I found that I couldn't repeatedly CQ without temperature creeping up so
> I
> > paused to around 50% duty cycle to stop that.
> >
> > However when sending QTC which amount to about 200 characters the
> > temperature would rapidly increase and eventually thermal trip.
> >
> > I took several actions to try to compensate:
> >
> > I opened the shack windows and bundled up. Shack then stayed at 60f or
> > below.
> > I immediately manually cranked the fan speed to max (5) when started to
> > send QTCs.
> > I rode the drive power downward as the power increased to stay below the
> > trip point of 105c.
> >
> > Upon taking all these actions I was able to eventually send the QTC
> > packets but it was unnerving and unexpected.
> >
> > This is a low serial number KPA1500 but with latest production firmware.
> >
> > What have others seen?
> >
> > 73
> >
> > jim ab3cv
> >
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

Jim AB3CV

Re: KPA1500 Thermal problems

It trips off at 105C.

It starts warning with a yellow indication at 100c

Power reduced to 1kw helped slow the rate of temperature increase but still
required a cold room and max fan speed at the beginning to contain it. It
never stopped climbing.

Jim ab3cv

On Mon, Nov 11, 2019 at 9:32 AM Fred Massey <[hidden email]> wrote:

> What output power did that reduce too ultimately, is 105c the design temp
> limit?
>
> On Mon, Nov 11, 2019 at 8:30 AM Jim Miller <[hidden email]> wrote:
>
>> " I rode the drive power downward as the power increased to stay below the
>> trip point of 105c."
>>
>> Should have been "as the temperature increased"
>>
>> jim ab3cv
>>
>> On Mon, Nov 11, 2019 at 9:03 AM Jim Miller <[hidden email]> wrote:
>>
>> > I participated in the WAE RTTY contest this past weekend and was having
>> > problems with thermal tripping.
>> >
>> > I have resonant antennas for 80, 40 and 20m and had SWR between 1:1 and
>> > 1.2:1, power nominally set between 1400-1500w.
>> >
>> > I found that I couldn't repeatedly CQ without temperature creeping up
>> so I
>> > paused to around 50% duty cycle to stop that.
>> >
>> > However when sending QTC which amount to about 200 characters the
>> > temperature would rapidly increase and eventually thermal trip.
>> >
>> > I took several actions to try to compensate:
>> >
>> > I opened the shack windows and bundled up. Shack then stayed at 60f or
>> > below.
>> > I immediately manually cranked the fan speed to max (5) when started to
>> > send QTCs.
>> > I rode the drive power downward as the power increased to stay below the
>> > trip point of 105c.
>> >
>> > Upon taking all these actions I was able to eventually send the QTC
>> > packets but it was unnerving and unexpected.
>> >
>> > This is a low serial number KPA1500 but with latest production firmware.
>> >
>> > What have others seen?
>> >
>> > 73
>> >
>> > jim ab3cv
>> >
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>>
>

AE4ED

Re: KPA1500 Thermal problems

Thank you for the information. RTTY contests are the acid test of an
amp....

On Mon, Nov 11, 2019 at 8:35 AM Jim Miller <[hidden email]> wrote:

> It trips off at 105C.
>
> It starts warning with a yellow indication at 100c
>
> Power reduced to 1kw helped slow the rate of temperature increase but
> still required a cold room and max fan speed at the beginning to contain
> it. It never stopped climbing.
>
> Jim ab3cv
>
> On Mon, Nov 11, 2019 at 9:32 AM Fred Massey <[hidden email]> wrote:
>
>> What output power did that reduce too ultimately, is 105c the design
>> temp limit?
>>
>> On Mon, Nov 11, 2019 at 8:30 AM Jim Miller <[hidden email]> wrote:
>>
>>> " I rode the drive power downward as the power increased to stay below
>>> the
>>> trip point of 105c."
>>>
>>> Should have been "as the temperature increased"
>>>
>>> jim ab3cv
>>>
>>> On Mon, Nov 11, 2019 at 9:03 AM Jim Miller <[hidden email]> wrote:
>>>
>>> > I participated in the WAE RTTY contest this past weekend and was having
>>> > problems with thermal tripping.
>>> >
>>> > I have resonant antennas for 80, 40 and 20m and had SWR between 1:1 and
>>> > 1.2:1, power nominally set between 1400-1500w.
>>> >
>>> > I found that I couldn't repeatedly CQ without temperature creeping up
>>> so I
>>> > paused to around 50% duty cycle to stop that.
>>> >
>>> > However when sending QTC which amount to about 200 characters the
>>> > temperature would rapidly increase and eventually thermal trip.
>>> >
>>> > I took several actions to try to compensate:
>>> >
>>> > I opened the shack windows and bundled up. Shack then stayed at 60f or
>>> > below.
>>> > I immediately manually cranked the fan speed to max (5) when started to
>>> > send QTCs.
>>> > I rode the drive power downward as the power increased to stay below
>>> the
>>> > trip point of 105c.
>>> >
>>> > Upon taking all these actions I was able to eventually send the QTC
>>> > packets but it was unnerving and unexpected.
>>> >
>>> > This is a low serial number KPA1500 but with latest production
>>> firmware.
>>> >
>>> > What have others seen?
>>> >
>>> > 73
>>> >
>>> > jim ab3cv
>>> >
>>> ______________________________________________________________
>>> 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
>>> Message delivered to [hidden email]
>>>
>>

Richard Zalewski

Re: KPA1500 Thermal problems

I operated the contest with over 1200 contacts. I never saw temps over
80c. I too have a low serial number but have installed all the firmware
updates. Only on 40m did I hear the fan speed get to a very high speed. I
was running about 1200w at all times.

Richard
*W7ZR* ex:5C5Z, CN2ZR, K2JSP, W6SBZ, W7KXR, K9ZIJ, W9KNF, W0KDF, W0MQU,
J68ZR, KC6ZR, PJ4/W7ZR, KH2,W7ZR, KH6/W7ZR, V31ZR, VK4AAZ, XE2DV

*Be joyful in hope, patient in affliction, faithful in prayer*

On Mon, Nov 11, 2019 at 7:44 AM Fred Massey <[hidden email]> wrote:

> Thank you for the information. RTTY contests are the acid test of an
> amp....
>
> On Mon, Nov 11, 2019 at 8:35 AM Jim Miller <[hidden email]> wrote:
>
> > It trips off at 105C.
> >
> > It starts warning with a yellow indication at 100c
> >
> > Power reduced to 1kw helped slow the rate of temperature increase but
> > still required a cold room and max fan speed at the beginning to contain
> > it. It never stopped climbing.
> >
> > Jim ab3cv
> >
> > On Mon, Nov 11, 2019 at 9:32 AM Fred Massey <[hidden email]> wrote:
> >
> >> What output power did that reduce too ultimately, is 105c the design
> >> temp limit?
> >>
> >> On Mon, Nov 11, 2019 at 8:30 AM Jim Miller <[hidden email]> wrote:
> >>
> >>> " I rode the drive power downward as the power increased to stay below
> >>> the
> >>> trip point of 105c."
> >>>
> >>> Should have been "as the temperature increased"
> >>>
> >>> jim ab3cv
> >>>
> >>> On Mon, Nov 11, 2019 at 9:03 AM Jim Miller <[hidden email]> wrote:
> >>>
> >>> > I participated in the WAE RTTY contest this past weekend and was
> having
> >>> > problems with thermal tripping.
> >>> >
> >>> > I have resonant antennas for 80, 40 and 20m and had SWR between 1:1
> and
> >>> > 1.2:1, power nominally set between 1400-1500w.
> >>> >
> >>> > I found that I couldn't repeatedly CQ without temperature creeping up
> >>> so I
> >>> > paused to around 50% duty cycle to stop that.
> >>> >
> >>> > However when sending QTC which amount to about 200 characters the
> >>> > temperature would rapidly increase and eventually thermal trip.
> >>> >
> >>> > I took several actions to try to compensate:
> >>> >
> >>> > I opened the shack windows and bundled up. Shack then stayed at 60f
> or
> >>> > below.
> >>> > I immediately manually cranked the fan speed to max (5) when started
> to
> >>> > send QTCs.
> >>> > I rode the drive power downward as the power increased to stay below
> >>> the
> >>> > trip point of 105c.
> >>> >
> >>> > Upon taking all these actions I was able to eventually send the QTC
> >>> > packets but it was unnerving and unexpected.
> >>> >
> >>> > This is a low serial number KPA1500 but with latest production
> >>> firmware.
> >>> >
> >>> > What have others seen?
> >>> >
> >>> > 73
> >>> >
> >>> > jim ab3cv
> >>> >
> >>> ______________________________________________________________
> >>> 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
> >>> Message delivered to [hidden email]
> >>>
> >>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

Jim AB3CV

Re: KPA1500 Thermal problems

In reply to this post by Jim AB3CV

Unit is now in transit to Elecraft for repairs.

Jim ab3cv

--
Sent from: http://elecraft.365791.n2.nabble.com/
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Jim Miller

Re: KPA1500 Thermal problems

In reply to this post by Jim AB3CV

Unit is now in transit to Elecraft for repair.

Jim ab3cv

> On Nov 11, 2019, at 9:03 AM, Jim Miller <[hidden email]> wrote:
>

I participated in the WAE RTTY contest this past weekend and was having problems with thermal tripping.

I have resonant antennas for 80, 40 and 20m and had SWR between 1:1 and 1.2:1, power nominally set between 1400-1500w.

I found that I couldn't repeatedly CQ without temperature creeping up so I paused to around 50% duty cycle to stop that.

However when sending QTC which amount to about 200 characters the temperature would rapidly increase and eventually thermal trip.

I took several actions to try to compensate:

I opened the shack windows and bundled up. Shack then stayed at 60f or below.
I immediately manually cranked the fan speed to max (5) when started to send QTCs.
I rode the drive power downward as the power increased to stay below the trip point of 105c.

Upon taking all these actions I was able to eventually send the QTC packets but it was unnerving and unexpected.

This is a low serial number KPA1500 but with latest production firmware.

What have others seen?

73

jim ab3cv
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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