Hum on my carrier w/ Henry 2K-4

[KX5JT]

The top is well ventilated....

[DMOD]

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.

I too am concerned over HV safety, but before everyone gets overly excited (no pun intended),   there are two top covers or panels on the Henry; both being perforated. (At least that is how my Henry is configured). And it appears to be the same pedestal type 2K-4 as mine.

The top cover covers the whole top rectangle including the RF deck and front panel area, and then there is the RF deck cover directly below it, shielding the operator from direct contact with HV components.

The RF deck perforated cover presses against a HV switch such that when this cover is removed, the HV is shorted, providing an interlock capability.

What I found was the RF deck will run much cooler if the "TOP" panel is removed, but still keeping with the RF deck cover, and this provides a measure of safety against HV accidental contact. The top cover, although being perforated itself, DOES restrict air flow.

Now one could install higher flow fans or whatever method that will improve cooling as well, and those would not be off the table by any means.

Phil - AC0OB

[Steve - WB3HUZ]

I've seen a few Henrys where a hole was cut in the top and the inner cover and pipe (or similar) inserted from the tops of the chimneys out to the top of the cabinet. It might be over kill but getting the hot air completely out of the cabinet is probably a good thing.

[K1JJ]

Or you could do like Tom Vu:  Remove the stock homo-fan at the bottom and seal it with an aluminum plate. Then cut a 4" hole in the back below the final cage and install a 4" pvc pipe flange. Seal it for good pressure thru the chimneys.  Run 4" flexible fiberglass hose outside the house wall - where there's a Variac'd squirrel cage waiting to blow in 30F winter air...    It runs coooool and VERY quiet....

T

[W3RSW]

Those holes in the stock cover amount to no more than, say, a one inch hole equivalent, or whatever.
 I bet it isn't much.

 Neatest idea and also keeps the cover unmolested is to take an 8 x 8 wooden cigar box top (the smaller) or equivalent, cut a fan hole in it,  mount a 4" fan on it, put some felt or foam strips around the lips, place it on top blowing upwards to put most of the amp's cover holes under negative pressure.  You'll be surprisied how cool the whole thing runs.

You'd thnk it would just suck air in through the other holes on the top and leave the rig hot but I assure you I've cooled everything from a Ranger to an HQ 110 simply by sliding it from one rig to another.

If the edges of the box are even all the way around, you don't even need sealing felt or strips.

[K5UJ]

I too am concerned over HV safety, but before everyone gets overly excited (no pun intended),   there are two top covers or panels on the Henry; both being perforated. (At least that is how my Henry is configured). And it appears to be the same pedestal type 2K-4 as mine.

Didn't know that Phil; I apologize.  Thought the days of double covers only extended through the great Ham TVI plague of the 1950s when TV was new and suddenly hams were innocently wrecking channel 2. 

Removing one cover is probably a good idea -- and cutting a hole over the tubes and putting in expansion steel may be a good thing too but you have to not care what your gear looks like (I don't care what my gear looks like  ).   Anyway, two covers is another sign of good building. 

73

Rob

[DMOD]

Didn't know that Phil; I apologize.  Thought the days of double covers only extended through the great Ham TVI plague of the 1950s when TV was new and suddenly hams were innocently wrecking channel 2. 

Hey no problem Rob.

I think when John took the pictures, he had removed both top covers to give everyone a sneak peak of the (can I say  - virgin?) RF deck and it's components.

In fact, I believe there are like two interlocks on this puppy. One is on the RF deck cover and one on the back cover for access to the power supply. The one on the back cover is a reed switch on the chassis with the magnet on the back panel.

When I finally got mine into the basement shack, I opened all covers, vacuumed,  inspected all components for heat and corrosion, and cleaned all switches and contacts.

Imagine my suprise when I replaced the RF deck cover for a dummy load test and the thing didn't power up.

Duh? I then found the reed switch. and all was well.

Phil - AC0OB

[KX5JT]

UPDATE:

I ordered a grounded grid bifilar wound ferrite rod type filament choke from RF Parts.  20 bucks.  I was able to replace the stock torroid filament choke.

NO MORE HUM!  SUCCESS!!!

73 John

[WA1GFZ]

BTW the inductance of a B&W FC 30 winding is 17uh

[W2VW]

BTW the inductance of a B&W FC 30 winding is 17uh

Unless you drop it.

[W3TDH]

Congratulations
--
Tom W3TDH

[Steve - WB3HUZ]

I becomes more inductive then. It will induce much cursing.

BTW the inductance of a B&W FC 30 winding is 17uh

Unless you drop it.