[Heathkit] Re: HW-16 and hum.

[Garey Barrell]

Ken -

We used the HW-16 as an Autostart RTTY radio back in the late 60's.  
They were run on 14.075 MHz, crystal controlled, with a Heath 400 Hz 
crystal filter from the SB-300 in the IF.  I seem to recall that there 
was a hum problem, and it was traced to orientation of the AF output 
transformer.  It was at the other end of the chassis, but the windings 
of the two transformers were in the same "plane".  I think moving it 
from the back wall to the side wall reduced the hum considerably.

Also may be all wet!  The old memory bank ain't what it used to 
be......  :-)

73, Garey - K4OAH
Atlanta

Drake 2-B, 4-B & C-Line Service Data
<http://www.k4oah.com>



Kenneth G. Gordon wrote:
> 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.
>>