[Hammarlund] My HQ-170A is a hummer!

[JOHN M IVERSON]

CRAIG,I think that you may be picking up hum from the power tx magnetic
field.
to verify that put a peice of heavy steel or even a pipe nipple, a big
one, between the output
and pwr txs. Even rotating the output tx for minimum hum may help. This
is why
some power amps have the output tx rotated a bit to minimise the hum.
experiment, I think that this is your problem.
this is why most of the older H-C radios have a steel case around the
coil and laminations.
  Jack                      jackiv@juno.com


On Thu, 19 Feb 2004 22:53:30 -0500 "Craig Roberts" <crgrbrts@verizon.net>
writes:
> Well, I've been using my eBay queen ex-basket case HQ-170A as a sort 
> of
> Hammarlund lab -- I mean, what did I have to lose?
> 
> As a last step in restoration, I've installed a high quality audio 
> output
> transformer to replace the low-end universal transformer stuck in 
> there by a
> previous owner. (One wonders what happened to the factory job).  My
> transformer's a 5K to 3.2 ohm unit and, combined with my newly 
> acquired
> SP-200 speaker, puts out wonderfully high fidelity audio.
> 
> And that's the problem. The frequency response is now such that I'm 
> hearing
> a distinct 120 cycle hum under the signals. The hum is independent 
> of the AF
>-------------------SNIP------------------