[Amps] Alpha 76A - 120hz hum on 160m only

[Jim Barber]

Hi Jim,

Yep, we tried AM and SSB both.
The filter caps are brand new, and I also changed the bleeder/equalizer 
resistors, as well as the other carbon comps on the control board, since 
they were drifted out of tolerance.

I'm working on the plate choke bypass caps, bias line bypass, etc.
If I wasn't so nervous about it I'd hook up the fancy HV probe I
bought for my DSO and actually take some measurements. Just color me 
chicken... :-)

Thanks es 73,
Jim N7CXI

On 10/17/2013 9:35 PM, Jim Brown wrote:
> On 10/17/2013 7:43 PM, Jim Barber wrote:
>> 160M AM, (100W carrier, 400W PEP) into two different antennas and all
>> said the hum was very loud. Move to 75M or higher and it
>
> Are you running AM on the other bands too? If it's not there (or not
> strong) on SSB, I'd suspect filter cap(s) in the HV string.  I don't
> work AM, but on CW, I've had exactly that symptom, with exactly that cause.
>
> 73, Jim K9YC
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