On Nov 11, 2006, at 10:54 AM, Robert B. Bonner wrote:
Well I do have responses for the comments.
I do currently own a 3K-A. Have had virtually all of them in the past.
Also have owned an L4B, Swan Mark II never SB-220 or TL-922 however I've
worked on almost everything at one time or another.
The problem with Henry's and Heath's design is the SOCKETS. The Johnson
socket mounted below the chassis on 4 bent metal brackets is the problem.
The little holes in the Johnson socket were matched to the 4-XX series of
tubes. 4-65, 4-125, 4-250 and were designed before they developed tubes the
size of 4-400, 3-400, 3-500. There is inadequate cooling around the bases
when using these sockets with the larger tubes.
I've seen Eimac 3-500's with the letters burned off one side in amps like
the SB-220.
I have never seen an amplifier with a cooling system like a SB-220's.
The correct Eimac air system sockets REALLY move air through them in all the
right places. For instance the 410's and 510's have a collar where you
actually hook up ducted air to the base.
The problem is that the 3-500Z air system socket requires a high- pressure centrifugal blower, and Ham amps used an ordinary centrifugal blower.
Back in 1970's it was recommended if you weren't using ducted air, that you
disassemble the sockets and hacksaw off the collar to allow even better
airflow during pressurized chassis operations.
My Ph.D. is in Physics, I spent a lot of my career after college in the
computer industry doing chassis design for a computer company. Basically
trying to put 10 pounds of electronic maird in a 5 pound box and cool it.
Chortle. Another useful French word.
In the lab we had a lot of temp probes in computers.
This was all PRE-IBM PC... Pc designs actually are some of the worst cooled
boxes around. :-( SO... The next problem with ham designs is the stupid
covers on the amps. Drilling holes to make the boxes look pretty. BAD
airflow. The best would be cut large holes with metal screens barely
blocking the airflow path.
That's how I do it. I also use a varnished cardboard flap that hinges up to let the air out.
It just doesn't look as pretty. A Heath cover
is a piece of junk. They paint more of the hole area closed than have
open...
The glass temperature is okay no matter what skeptics say.
...
So I think Between Jim VE7RF and myself we've answered why amps like Henry,
and The Sb-220 have had pin melting issues.
Only in a SB-220 when the fan motor bearings are not kept oiled
BOB DD
-----Original Message-----
From: ham_amplifiers@... [mailto:ham_amplifiers@...]
On Behalf Of pentalab
Sent: Saturday, November 11, 2006 6:25 AM
To: ham_amplifiers@...
Subject: [ham_amplifiers] Re: 3-500Z socket.... max current ratings
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
After my first 3-500 amp when I was 16 I always used sockets
and chimneys.
RICH SEZ.... Air system sockets and chimneys result in higher glass
temperatures than is the case with the transverse-fan cooling
system used in the SB-220 and TL-922.
### Nonsense. Depends on airflow... and speed of fan..or blower.
You def will get better, more uniform cooling with a blower and
chimneys... PROVIDED u use vertical finned anode connectors. With
chimneys... u def get better cooling of the pins.
I always felt it allowed the envelopes of the tubes to evenly
cool around the tubes. The tube pins get coolest direct air.
RICH SEZ... So why does the Henry 3K-A, which uses air-system
sockets and chimneys, have a history of melting solder out of tube
pins #1 and #5 ?
### Dunno... my guess is, since the 3K-A runs 4 kv.. and >2 kw
out... that some bozo at Henry screwed up. Maybe they use lousy
sockets.. with too much contact resistance. Who knows. Their
anode connector's may well be a problem. Lot's of homebrew 3-
500Z amps with chimney's... never a problem.
### There is hardly any air going through the pyrex coleman lantern
chimney's on a L4B... with it's puny... but quiet 1550 rpm
blower. No roasted ink either.... and no one ever melted solder
on pins 1+5.
### Use some heat sensitive paint(S)... like Eimac suggests... and
you can tell pretty quick... what's within spec.
Later.... Jim VE7RF
Yahoo! Groups Links
R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org
