[Elecraft] KPA1500 Thermal problems

[Jim Miller]

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 <fhmassey at gmail.com> 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 <jim at jtmiller.com> 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 <jim at jtmiller.com> 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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>