[Elecraft] KPA500 finals blown

[Bob McGraw K4TAX]

As applied to solid-state transmitters, ICAS does not imply reduced 
device life, as unlike vacuum tubes, the RF power devices are not 
regarded as consumables. Rather, ICAS in a solid-state environment 
implies de-rating to keep the device junction and case temperatures 
within their maximum ratings. Thus, ICAS suggests a limited operating or 
'on' period followed by an 'off' or standby period of at least the same 
or longer duration, whilst CCS assumes continuous, key-down operation at 
reduced output (assuming the same heatsink area and/or fan air-flow 
rating for both applications).

Typically, a PA cooling system should be designed to keep the device 
case temperature in the range 70 ~ 80ºC (158 ~ 176ºF) at 25ºC (77ºF) 
ambient, for a 30-minute SSB voice transmission or a 5- to 10-minute 
“key-down” CW transmission at rated output. These are minimal duty cycle 
values for an amplifier operating in average amateur service. Longer 
“key-down” intervals, necessitating larger heat-dissipating surfaces and 
greater air circulation, are required for contest operation or at high 
ambient temperatures.


73
Bob, K4TAX



On 1/21/2016 8:44 AM, efortner wrote:
> I would like to know what the continous keydown power output rating is. The
> manual talks about ICAS. I know when I get on RTTY I does not take long for
> The fans to come up to full speed running 300 watts.
>
> Earl, K4Kay
>
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Nand
> Kishore
> Sent: Thursday, January 21, 2016 4:29 AM
> To: elecraft
> Subject: [Elecraft] KPA500 finals blown
>
> KPA500 shut off with a bang while operating RTTY @300W.
>
> Antenna is a steppir beam.
>
> On opening the KPA500,found 2 ceramic? caps of VRF2933
> adrift with underside of the said caps,black.
>
> Have written to support.Is this the first time this has happened
> in a KPA500?
>
> 73 and HNY,
> Nandu
> VU2NKS
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