[Amps] 120 cycle hum from Henry 2K-4

[Carl]

After eliminating the driver hookup Id start by measuring the ripple on the 
HV. Find someone with a HV scope probe.

Carl
KM1H


----- Original Message ----- 
From: "Mike" <noddy1211 at sbcglobal.net>
To: <amps at contesting.com>
Sent: Thursday, February 18, 2010 6:48 PM
Subject: Re: [Amps] 120 cycle hum from Henry 2K-4


> What is your carrier power output from the amp on AM ?
>
> Mike
>
> -----Original Message-----
>
>
> I just acquired a Henry 2K-4 console linear amplifier.  I like to run
> AM as well as the other modes.  The Henry is rated for continous duty
> and as AM is closer to continous than SSB, I figured it was a good amp
> to have.  I'm very satified with the output from the two aging Eimac
> 3-500Z's but the 120 cycle hum that rides on the carrier is
> troublesome.  It's there whether I'm using my Kenwood TS-570 or my
> modified Heathkit DX-60 to drive it.  When I use the DX-60 (which I
> prefer for AM) making adjusting the tuning control will change the
> amplitude of the hum but never reduce it enough.  Seems like when in
> resonance the hum peaks too.  I have grounded the amp and the DX-60 via
> 10 gauge solid copper to an 8 gauge solid copper coming into the shack
> that's attached to the 8 foot copper clad steel ground rod right
> outside a couple feet away.
>
> For some perspective, I have no audible hum from the Heathkit SB-200
> and everything else the same.  The SB-200 is setup for 120 volts
> however, not 220/240.
>
> The Henry has full-wave bridge rectifier then uses an 8 henry (700ma)
> filter choke with an oil filled .1mf (7500v) in parallel then an oil
> filled 20mf (5000v) cap to ground.
>
> I've been told those oil filled caps rarely go bad and usually last
> longer than we do.  Any clues where I should be looking to solve this
> hum problem?  Of course it's not really noticible on SSB but I'm sure
> it's in there as well.
>
> 73 and thanks for any tips and patience with this !
> John  KX5JT
>
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