The 8' ground rod did absolutely nothing. But the bonding of the equipment
together did.
73
Jim W7RY
On Thu, Feb 18, 2010 at 8:30 PM, <johndtate@post.com> wrote:
> Maybe not the amplifier. Hums can be really tricky. When I did that
> check last night, I hadn't had the ground lug on the back of the Henry
> tied to my station ground. I grounded it very well with 10 gauge solid
> copper to the station ground (the 8 foot rod in the ground right
> outside) I just checked everything AGAIN and it looks like the hum is
> NOT audible to others now from the TS-570 in AM mode. I can see a very
> small amount on the scope but it's not audible so... I checked again on
> the DX-60 and without the amp on... there was the ripple. I think it
> IS 60 cycle. Someone last night on the air said it was 120 cycle but I
> listened to a 60 cycle hum audio file from the internet and guess what?
> Yep. I think after all the Henry is amplifying the DX-60's hum.
> Maybe because the SB-200 has a grounded three prong 117 volt plug...
> and the shield from the coax does tie the chassis's together, the hum
> was reduced? The DX-60 has a non-polarized 2-prong plug. I looked
> closer at the DX-60 cw on the scope by itself and the hum is there.
>
> I'm going to install a 3-prong grounded cord/plug on DX-60 and see if
> that works. Hums can be really tricky to figure out!! I think I'm
> finally on the right track and maybe it isn't the amp!! It's a
> learning experience for me! *crosses fingers*
>
> -----Original Message-----
> From: Steve Katz <stevek@jmr.com>
> To: johndtate@post.com; amps@contesting.com
> Sent: Thu, Feb 18, 2010 9:06 pm
> Subject: RE: [Amps] 120 cycle hum from Henry 2K-4
>
> Perfect! Then, it must be the amplifier.
>
> Have you confirmed it's really 120 Hz and not 60 Hz? If so, sounds
> like the choke tuning is incorrect and the tuning cap across the choke
> may have drifted in value. Of course, it could be the main filter cap
> as well.
>
> Oil filled caps do generally last a long time, but they can go bad.
> Have you opened up the power supply covers to look inside and see if it
> leaked?
>
>
> -----Original Message-----
> From: johndtate@post.com [mailto:johndtate@post.com]
> Sent: Thu 2/18/2010 6:27 PM
> To: Steve Katz; amps@contesting.com
> Subject: RE: [Amps] 120 cycle hum from Henry 2K-4
>
> Steve, It's also present in CW mode. It's on the scope and it's heard
> in my receiver and others. It's present whether I use the DX-60 or the
> TS-570 in any mode that produces a carrier, with or without audio.
>
> -----Original Message-----
> From: Steve Katz <stevek@jmr.com <lt%3Bstevek@jmr.com>>
> To: TexasRF@aol.com; johndtate@post.com; amps@contesting.com
> Sent: Thu, Feb 18, 2010 8:08 pm
> Subject: RE: [Amps] 120 cycle hum from Henry 2K-4
>
> 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@contesting.com on behalf of TexasRF@aol.com
> Sent: Thu 2/18/2010 5:34 PM
> To: johndtate@post.com; amps@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@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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