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

[larry roohr]

Craig,

In case you havnt seen it yet, there is an excellent article on 'hum' by 
N0DMS in the July 2002 Electric Radio, #158.

Larry, kz0e


Craig Roberts wrote:

>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
>Gain and RF Gain controls, so it's at the end of the chain. Now, the problem
>could be lead dress, I suppose. There's quite a distance between the
>transformer and the speaker terminals and the output lead runs right next to
>the power supply components.  Since my receiver was modified and somewhat
>butchered when I got it, I don't know where the lead's really supposed to
>be -- suspended under the components?--snugged down against the chassis? Can
>anyone tell me, please?  Also, if you have any hum reduction tips, please
>share them.
>
>Also, I'd love to get an original 170A audio output transformer (with the
>dual 3.2 ohm and 500 ohm secondaries) if anyone's got such an animal to
>sell.
>
>Many thanks and 73,
>
>Craig
>W3CRR
>
>
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