[Elecraft] KPA500 hum; horrendous

[Macy monkeys]

I suspect that may be the case, Bob. I will wait until I hear from tech support before I pop  open then amplifier for a look-see. It is factory built.

Regarding power output, I was incorrect. On 80 and 40 meters I am seeing similar outputs as you. I am on a 240 source, HV is 74 volts. 

John K7FD

> On Nov 7, 2018, at 5:19 AM, Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:
> 
> Zero hum from mine.  From other comments, be sure the power transformer is correctly installed and secured.  It may have moved during transportation if you purchased a factory built unit.
> 
> As to 20 watts drive and 350 watts out, what bands?    With 20 watts drive from my K3S I see 450 to 550 watts out on all bands as seen on the amp LED indication and on an external {Bird 43} meter.    The HV is 62 volts and the current is 11.5 amps into a dummy load.  Amp is operated from a 240 source.
> 
> 73
> 
> Bob, K4TAX
> 
> 
>> On 11/6/2018 10:47 PM, Macy monkeys wrote:
>> I'm certainly having my troubles with this new KPA500. The level of hum is unacceptable.
>> 
>> The manual says it is normal to hear hum. With 20 w drive I'm getting 350 watts out but the hum is horrendous when I send CW. SSB not so bad. Is this level of hum normal during keydown? It's room filling!
>> 
>> John K7FD
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