[Heathkit] Re: HW-16 and hum.

[Kenneth G. Gordon]

Thank you, Miles. Although I replaced ALL the filter caps some 
time ago, it most certainly IS possible that one has failed.

However, I do know that a lot of HW-16 users have complained of 
hum at low audio levels, even with good filter caps.

Personally, I think it has to do with placement of wires, but have not 
yet tracked the problem down.

The leads to and from the volume control are 100% foil shielded 
types. Disconnecting that source completely from the input of the 
1st audio stage doesn't change the hum in any way.

What I may do is to add a 60 Hz series tuned trap at the input of 
the 2nd audio stage. If my calculations are correct, a 10 mfd 
tantalum cap in series with a 270 ohm resistor MIGHT work. If the 
resistor doesn't do it, then a .7 H choke will.

If this doesn't work, I'll connect such a trap at the OUTPUT of the 
2nd audio amp.

On 29 Jun 2006 at 12:41, Miles Anderson wrote:

> The most likely source of audio hum in your HW-16 is an open (or
> partially open) high voltage filter capacitor.

Ken W7EKB