[Elecraft] KPA-500 HUM

[Eric Swartz - WA6HHQ, Elecraft]

When the back panel switch is on, the low voltage power supply for the 
front panel is still on, allowing the microprocessor to read the front 
panel 'power' switch and talk over RS-232. A low level of power supply 
hum from this small transformer is totally normal in this case. Of 
course, turnig off the rear switch on the KPA500 shuts down everyhting. 
Its perfectly OK to use the rear switch as the main on/off power control.

The KPA500 front panel power switch is a 'soft' switch that controls the 
HV supply relay etc. This allows remote control over RS-232 to power 
up/down the amp etc.

73, Eric   WA6HHQ

---
www.elecraft.com


On 8/3/2011 1:09 AM, Ken Chandler wrote:
> Hi
> I took part in IOTA contest at the weekend in the unassisted category, CW, high power.
> The KPA-500 was used for the first full 24hrs contest here with M3i call-sign and I did give it a darn good work-out end result performance was just fab.
> No hang-ups, instant power, band change, big pile-ups lots of QSO's LOTS of fun.
> It just loofed along, the fan came on occasionally but was not loud, my PC's fan is louder than the amp.
> HOWEVER
> after the contest,  pc switched off, k3 on, amp still on in standby mode,
> Their is a HUM from the amp and was fairly noticeable.
> Turning off the rear switch cured it!!!
> Perhaps one for the engineers to look at, as I'm sure they will, and are already on the case!!!!
>
> Ken..G0ORH / M3i KPA-500 sn 212
>
> Sent from my iPhone
>
>
>
>
>
> On 3 Aug 2011, at 07:08, Klaus Koppendorfer<KK at ccf.net>  wrote:
>
>> discussion is drifting away to amplified speakers but there is realy a problem with
>> HUM comming from KPA500
>>
>> 1) HUM during transmit
>> 2) HUM somes sometimes when the KPA500 is off, but on line and backswitch on
>>
>>
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