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

[Dan]

There is a good discussion of the power supply in the 2K4 here about 
half way down.
http://www.qsl.net/i0jx/supply.html

73, Dan, N5AR

Steve Katz wrote:
> The Henry amps I've had (several over the years) when operating properly produce negligible hum modulation at full rated power.
>
> But I asked earlier if he found the same evidence of ripple when he used "CW" (vs. "AM") on his exciter and I don't think I've seen that answered.
>
> If "yes," then it could well be a PS issue in the Henry; if "no," then it's something else.  Usually if the PS develops unreasonable ripple, its regulation will also suffer since they're both based on the same factors.
>
> Steve WB2WIK/6
>
> -----Original Message-----
> From: amps-bounces at contesting.com on behalf of TexasRF at aol.com
> Sent: Thu 2/18/2010 5:34 PM
> To: johndtate at post.com; amps at contesting.com
> Subject: Re: [Amps] 120 cycle hum from Henry 2K-4
>  
>
>  
> John, every dc power supply has some ripple. If the power supply has a  
> nominal output of 2500vdc and the ripple voltage is 125 vpp then that would be  
> 5% peak modulation or 3.5% rms. I think this is 20log .035 or 29 dB below 
> the  carrier in this case.
>  
> So, how many dB down do you think your hum level is?
>  
> I don't know how to calculate ripple on a Henry type power supply; perhaps  
> some here knows how or has actually measured one.
>  
> 73,
> Gerald K5GW
>  
>  
> In a message dated 2/18/2010 5:31:28 P.M. Central Standard Time,  
> johndtate at post.com writes:
>
> 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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