Hum on my carrier w/ Henry 2K-4

[DMOD]

The meter is showing about 3400 volts idle and 3250 on TX.  I'm showing 242 volts AC at the outlet, a bit high I suppose.  I wonder about the filament voltage, if that is higher than 5 volts due to the high AC.

Interesting in that my AC voltage at the dedicated AMP outlet is about the same. The output of the filament winding is about 10.35VAC at pins 7 and 9 of the TB201 terminal strip, so that is not excessive. The filament current has to go through the filament choke after that so there will be a slight drop before it gets to the filaments.

Me thinks your mike preamp walwart could be the major cause of hum, especially if some RF is getting into it.

As others have suggested, check out the AC grounding and set up some star grounding for your system.

Phil - AC0OB

[KX5JT]

Here's a professional grade power strip surge supressor from price wheeler but it ain't cheap:

http://brickwall.thomasnet.com/item/standard-surge-protectors/ten-outlet-rackmount-modular-surge-protectors/pwrm15?&forward=1

you get what you pay for.

HAH!  That would be a riot! Using a $400+ surge protector on a 50 dollar transmitter!

[WQ9E]

As Rob said, on the power strips you truly get what you pay for!  A few weeks ago a colleague pulled her cell phone charger out of her new cheapo china power strip and the strip guts came out with the charger.  I am pretty sure she said Oh S**T but the snapping sound of load and neutral making contact drowned out the second word

The breaker tripped and the carnage was cleaned up.  Decent metal strips are the way to go.

[KX5JT]

And the strip was probably not the culprit, but the other items on it may have contributed some, some walwarts. 

My hum is not completely cured yet.  It's definetly 60 cycle hum.  It's still there and audible but much better than when I started.   It's on the DX-60, not sure if it's B+ ripple or being picked up from something magnetically.

[ke7trp]

Open transmitter.  Double UF of filter caps.  Problem now solved.

C

[KX5JT]

Open transmitter.  Double UF of filter caps.  Problem now solved.

C

Rahjah Rahjah Clark

[W4EWH]

Here's a professional grade power strip surge supressor from price wheeler but it ain't cheap:

Speaking of power strips, I've been looking for the extra-long model that lets me plug in a bunch of wall-warts without covering adjacent outlets. Staples doesn't have them anymore: does anyone know where I can get them online?

Bill, W1AC

[KM1H]

Open transmitter.  Double UF of filter caps.  Problem now solved.

C

Rahjah Rahjah Clark

More likely heater-cathode leakage in the tubes.  A stock DX-60 with good (new) caps doesnt hum; I use one into various amps with no hum reports from critical listeners.

Carl

[KB2WIG]

 " Staples doesn't have them anymore: does anyone know where I can get them online?"
 Go to homely despot, get a wiremold strip, buy some sjt cordage and a heavy duty wall plug...... it'll cost you a few bucks, but you'll  have a nice strip

OR

 ...buy it already made.

Wiremold Plugmold 6 Outlet, Ivory, Hardwire, 3 Ft.
Model # V20GB306+     Internet/Catalog # 100657491     
Store SKU # 340337

Wiremold makes lots 'o stuff that is usefull for the professional lectrical instilator. Going to places like the despot lets u see stuff, and it may give u an idea or two. Going to a real electrical outlet may be intimidating to some, and its not set up fer looking at the stuff. The counter people usally sell to them thats knows whats theys wants.

klc

[W3TDH]

John

W1AC should have warned you that you would stir up  the grounding grouch.  The words "right outside the shack" have me wondering how far from the foundation wall your driven rod grounding electrode is.  If it is not at least it's own length away from the wall it's effectiveness in providing lightning protection for your coax entry bulkhead is badly compromised.  To be effective the driven rod electrode must have a complete shell of undisturbed soil around it that is at least the radius of the rod length.  The rod should be connected to the single point ground with a number two bare copper conductor or, better still, with a copper flashing ribbon of at least 22 gauge and three inches width.  Special clamps are used to attach the copper ribbon to the rod.  If you live in a high incidence lightning area you should use at least three rods that are twice their own length apart.  You connect these to each other with the same gauge of conductor that you used to connect your single point ground to the first rod.  Keep any bends in the grounding electrode conductors gentle.  If you have any other questions just ask. 

--
Tom Horne, W3TDH

This is why I love AMfone!  I'm going to nail this puppy with help from this community.  

JN, Looks like I will have to get some more #8 or #10 and tie my station ground to the service round.  I think it's about 30 to 40 feet away.  I will do that at my earliest opportunity.  (snip)  In my case I run a balanced antenna (of the dipole variety) but I have a "station ground" which I always read I needed and it consists of an 8 foot copper clad steel rod right outside the shack wall.  #8 gauge solid copper coming into my shack and at this point, my amps, my dx-60, my antenna tuner all have runs from chassis ground bolts to the entry point.  I don't have each one going all the way out to the rod but they do each tie in as close as possible to it without leaving the shack.  Now from what I am understanding from you JN, I should also run a wire, in the most direct, practical path between my service ground rod at the electrical box (in my case it's under the service box that is mounted on a wooden pole from which the mains are being fed from overhead at the street and xformer there).  

John KX5JT

[KX5JT]

Well the hum is fairly tame and only slightly audible now.  I had a private email from someone who said they had a 2k5D model Henry that had hum, especially on 80 meters.  Mine does seem more prominent on 80 meters.  He said after trying everything everyone suggested, the fix was replacing the filament choke with one from RF Parts.  My 2K-4 parts list shows a torroidal filament choke, not a bifilar choke.  Hmmmm..... any thoughts?

John

[Roy K8VWX]

        Check with w8er Larry - He hangs out in the mornings around 3705 on 8o meters. The Henry had a problem I beleive with the bifalar wound filament choke. Larry tried everything including new filters. I'm not sure what model he had but it was a hum problem when running AM. All was OK on SSB.  ( I think he gave up on it and sold it to another ham who new of the problem and repaired it ) He may have bought it back now?

[KX5JT]

       Check with w8er Larry - He hangs out in the mornings around 3705 on 8o meters. The Henry had a problem I beleive with the bifalar wound filament choke. Larry tried everything including new filters. I'm not sure what model he had but it was a hum problem when running AM. All was OK on SSB.  ( I think he gave up on it and sold it to another ham who new of the problem and repaired it ) He may have bought it back now?

Thanks Roy, Yes I would love to change the filament choke.  Those are only about 20 bucks from RF parts but here is what puzzles me... the Henry 2K4 manual parts lists doesn't say "bifalar wound filament choke".  Instead it says TORROIDAL filament choke.  I'm going to have to track it down on my amp and see if a bifalar can be physically placed in there instead.  I imagine it would, there seems to be plenty of room in the console.  It may be a few days before I can do it, but whatever I find I'll certainly keep the thread posted.

John

[K5UJ]

when doing anything with the filament choke take care to not take too much liberty with the length of the wires or the gauge.   Usually these two things are part of the amp's engineering to get the fil. v. at 5 v. 

I wonder if there might be some problem with the caps that are usually in there between the cathode's RF exciter and the filament supply? 

While you are getting into the amp you may as well take a good look at the parasitic supressors on the plates.   They are usually an inductor and resistor parallel to each other and in series, one pair each between each anode and the h.v. choke.   Typically you'll have a coil with one to three turns around 1/2 inch diameter and 1/4 inch space between turns and a 100 ohm 2 or 3 watt carbon resistor, however in later amps you may find a metalized resistor.   Take a look at the solder connections on these components and make sure they have not deteriorated with heat.  Check the resistors for the same thing.  Sometimes the solder used isn't a type that stays hard if the lead to the anode gets real hot (like what can happen with an AM buzzard transmission and insufficient RF deck cooling )  The leads to the plates, and from the parasitic suppresser circuit to the tune cap should not be long and thin.  They should be no longer than necessary and some kind of solid flat strap copper or silver plate at least 1/8 inch wide (but wider is better).   I imagine this is something Henry got right--I'd be surprised if they used skinny wires.

[K1JJ]

John,

An easy test:

To increase the impedance of the fil choke, slip some ferrite cores, preferably type-43, over BOTH fil lead wires.  ie, BOTH wires run thru the same core hole.  Maybe there's enuff end lead length to do this, or just add some on if possible.  It can't hurt to have some extra inductance there even if it doesn't help the problem.

My linear uses just cores, about 10" in length total, slipped over the fil leads. No reason for the ferrite rods or coil turns if enuff cores are slipped on.

In your case, add a few and see if the problem goes away.

T

[Roy K8VWX]

        Yes indeed John the Henry uses a torroidal choke - Talked to w8er this morning on 3705 and he said the torroidal would have to be rewound with more turns but the easy way out was to install the old trusted bifilar .(That was my goof on my posting calling the original choke a bifilar). This drove Larry crazy tracking this trouble down.I think there is a posting on Google about this type of hum problem with the Henry's. Good Luck / Roy - 73

[KX5JT]

when doing anything with the filament choke take care to not take too much liberty with the length of the wires or the gauge.   Usually these two things are part of the amp's engineering to get the fil. v. at 5 v. 

I wonder if there might be some problem with the caps that are usually in there between the cathode's RF exciter and the filament supply? 

While you are getting into the amp you may as well take a good look at the parasitic supressors on the plates.   They are usually an inductor and resistor parallel to each other and in series, one pair each between each anode and the h.v. choke.   Typically you'll have a coil with one to three turns around 1/2 inch diameter and 1/4 inch space between turns and a 100 ohm 2 or 3 watt carbon resistor, however in later amps you may find a metalized resistor.   Take a look at the solder connections on these components and make sure they have not deteriorated with heat.  Check the resistors for the same thing.  Sometimes the solder used isn't a type that stays hard if the lead to the anode gets real hot (like what can happen with an AM buzzard transmission and insufficient RF deck cooling )  The leads to the plates, and from the parasitic suppresser circuit to the tune cap should not be long and thin.  They should be no longer than necessary and some kind of solid flat strap copper or silver plate at least 1/8 inch wide (but wider is better).   I imagine this is something Henry got right--I'd be surprised if they used skinny wires.

Just to give you an idea of how this Henry is built and rated for continuous duty and to have a looksee at the parasitic suppressors, here it is:

[K5UJ]

I like the chimneys.  That's the way to cool the 3-500s (in my opinion).  I like the straps to the plates.  I can't see the resistors inside the suppresser coils but I see what I think are the blocking caps.  That's a nice looking set of tank coils.  No worry about having one overheat.  It looks like the connection to the tune cap from the blocking caps is very short, as in caps bolted right to the air variable.  That's very good.  The two variables are installed well--a lot of bonding to the chassis from what I can see of the load cap.  Looks like you have slug tuned input matching.  That's good too.  I wish I had that.  Thanks for posting the photo.  It is always interesting to see how manufacturers do things.  Nothing fancy with bells and whistles but what's there is stout.  That's what you want.  Let others spend thousands on flashing LEDs and automatic controls.

Rob

[KX5JT]

Inside each parasitic choke coil are a pair 150 ohm 2 watt -+10% carbon resistors in parallel.
That was common in the 60's and 70's apparently. 

[K1JJ]

Yep they are beautifully built amps.  I have a 2K-3  -  basically the same thing still using 3-500Z's. I found it to be the cleanest 3-500Z amp of the two I own. I've done lots of mods to it, including strapping the grids directly to ground and using an outside blower for quiet cooling. Also built an  external 0-3500V supply. That amp really rocks at 3500V... 

I usually run it at about 1500V giving 100W carrier out, 600w pep as the AM "little rig" driven by the hi-fi FT-1000D. Finals barely get orange, though I run it hard occasionaly to getter the gas.

T

[DMOD]

Yep, they're built like tanks.

Just a couple of suggestions:

1. Run the amp with the top cover off. This allows better air flow and reduced RF deck heating.

2. Check the connection where the parasitic chokes meet the HV connection at the porcelain standoff. The hold-down screw loostens over time and if you get a high resistance connection, it will overheat and corrode and even arc.

3. Change the zener diode from a 10volt unit to a stud mounted, 50W, 6.8 volt unit. The Huzzman and others pointed this one out to me. The diode is located in the input box in far right corner (near back panel), looking from the front.

Phil - AC0OB

[DMOD]

Yep, they're built like tanks.

Just a couple of suggestions:

1. Run the amp with the top cover off. This allows better air flow and reduced RF deck heating.

2. Check the connection where the parasitic chokes meet the HV connection at the porcelain standoff. The hold-down screw loostens over time and if you get a high resistance connection, it will overheat and corrode and even arc.

3. Change the zener diode from a 10volt unit to a stud mounted, 50W, 6.8 volt unit. The Huzzman and others pointed this one out to me. The diode is located in the box in far right corner (near back panel), looking from the front.

Phil - AC0OB

[KX5JT]

Yep, they're built like tanks.

Just a couple of suggestions:

1. Run the amp with the top cover off. This allows better air flow and reduced RF deck heating.

2. Check the connection where the parasitic chokes meet the HV connection at the porcelain standoff. The hold-down screw loostens over time and if you get a high resistance connection, it will overheat and corrode and even arc.

3. Change the zener diode from a 10volt unit to a stud mounted, 50W, 6.8 volt unit. The Huzzman and others pointed this one out to me. The diode is located in the input box in far right corner (near back panel), looking from the front.

Phil - AC0OB

Phil, I'm looking at my manual and the diode inside that box is labeled D1 and it doesn't appear to be a Zener.  It's listed as a rectifier diode with a normal diode symbol on the schematic but maybe it is a Zener.  Anyway it is 10V and 1.2 amp rated.   Is this for the negative bias since the amp runs more than 2500 volts on the plates?  

Manual is on my site:

http://kx5jt.net/files/2K4%20Operating%20and%20Maintenance%20manual.pdf

[DMOD]

Yes, even though it is not shown as a zener, it is a zener (note reverse bias) and is one of the few weak components because it is underrated.

A 50Watt stud mounted version is best.

Phil - AC0OB

 

[K5UJ]

1. Run the amp with the top cover off. This allows better air flow and reduced RF deck heating.

Sorry Phil, but before someone gets killed I want to give my opinion -- this is an insanely bad idea.  If you did this where I work you'd get fired in a second.  The home should be no different.  If the cover restricts ventilation, do what I did -- cut a hole in the top over the tubes with a jigsaw, metal tooth blade, and bolt down some expansion steel over the hole.   If the cover is steel use cutting oil.

Rob