[Elecraft] KPA500 code oscillator

[W1GO (Joe)]

Al,

Quick follow-up on the KPA500 with the very loud buzzing transformer … after hours of disassembling, reassembling, tightening, etc., I couldn’t correct the problem and sent the unit back to the mother ship.  The transformer had a problem and was replaced.  I have heard from others that they were similarly told of a problem with transformers that would require replacement.  My unit is now wonderfully quiet.

My unit was a kit, but it makes me wonder if the “burn-in” of assembled units is simply an idle current test or if the unit it tested under load at different modes; my unit was quiet on SSB but ferociously loud on CW (even at 5W drive). It seems that would be pretty easy to detect in an assembled unit; kits are a whole other story.

In any event, aside for the $80+ it cost me to ship the unit back, all is well … and quiet.

Joe W1GO

> On Oct 23, 2016, at 5:46 PM, W1GO (Joe) <w1go at icloud.com> wrote:
> 
> 
> Hi all,
> 
> Finished assembly of KPA500 and a little surprised at the magnitude of hum / buzz during CW (no real issue on SSB); I've read about it but was surprised at just how pronounced it is.   I could use the KPA500 as a code oscillator for practice; no need to keep monitor turned on.  I've read most of the historical dialogue regarding methods to minimize "the buzz": use yellow wire tap, keep wires from touching chassis, make sure everything (including transformer) is good and tight, etc.  all those things are done with little positive impact.  I'm running off well regulated 240 VAC.
> 
> I just wonder if anyone has any other "secrets" they might share.  My code proficiency is not great, at this point, and having the KPA500 groan in response to my keying is somewhat distracting; even with headphones when monitor is turned up higher than usual.
> 
> Best regards,
> 
> Joe
> W1GO
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to w1go at icloud.com