Tom,

As others have said, the hum is probably coming from a vibration in the 
steel cover.  When I had an Astron RS35, I stuck a folded file card 
between the top edge of the front panel and the top cover and that 
really reduced the transformer hum that I could hear.

Bob, K8LR, [log in to unmask]

On 12/12/2015 3:01 PM, Tom Behler wrote:
> Hello, again, everyone.
>
>   
>
> I am now beginning to wonder if today is my day for Murphy to make a visit
> here, or just what exactly the deal is.
>
>   
>
> I was working a bit of the 10-meter contest today, and noticed a further
> problem with the hum issue on my new Astron RS35 power supply.
>
>   
>
> I'm not sure why I didn't notice it last night when I did my testing, but
> now, I find that whenever I transmit in CW at any power level-i.e. 5 watts
> or 100 watts, the hum on the RS35 slightly increases.  In other words, when
> I key down, I hear a slight, but noticeable increase in the hum at any power
> level.
>
>   
>
> So, now, I'm trying to decide whether I actually should return the supply to
> H R O.
>
>   
>
> I have my receipt and all other documentation, but I'm wondering whether the
> folks at HRO would see this as a significant enough of a problem for a
> product return.
>
>   
>
> The supply still seems to carry the load ok, and does put out what I would
> expect in terms of output power readings, but the hum issue is a noticeable
> one now, on several counts.
>
>   
>
> I don't mean to be obsessive about this, but I wouldn't expect to be dealing
> with this sort of issue with a newly-purchased power supply like this.
>
>   
>
> I'd continue to be interested in anyone's thoughts.
>
>   
>
> Tom Behler: KB8TYJ
>
>