On Nov 12, 2006, at 3:05 AM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
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.
### Drake uses the same Johnson sub mounted sockets on the L4B.
[came out in 1969].. on aluminium cylinder standoffs. The 3-500Z
spec is for only .08" h2o... which is easy to achieve. That's
zip..pressure wise. Drake used real Eimac SK-410's on the older
plane jane L4 [1964]
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.
RICH SEZ...I have never seen an amplifier with a cooling system
like a SB-220's.
#### Sure their is. The Ten tec Centurion uses the same deal.
The chassis is raised UP, right where the sockets are. Resembles a
small box sitting on the chassis... with two[oposing] sides chopped
out.. so air can pass UNDERNEATH...and hit all the pins. The tiny
slots in the cab are where they screwed up... really restricts air
getting in and out.
... but the Heath SB-220 does not do this.
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.
### agreed. A 4-1000 Deck I bought from W6RU back in 1977 was
done exactly like that. Blower mounted below... with flexible
ducting that fit that collar like a glove.
## On HB 4-1000's... I carefully removed the pins from the SK-
510 socket... then sliced off that collar with a hacksaw... re-
asembled.. then installed em. In that case... blower was on rear
apron... pressurized the chassis.
The problem is that the 3-500Z air system socket requires a high-
pressure centrifugal blower, and Ham amps used an ordinary
centrifugal blower.
### See my note above. A 3-500Z only requires a .08" h2o pressure.
Correct, but Eimac's 0.82" water column spec is the pressure differential across the socket, and that usually means a fairly noisy blower.
... In this case.. the grilles are used to keep
fingers away from the anodes... yet let air pass freely... plus
they look good.
RICH SEZ... 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.
### It would look like hell! Now that's what I call "K-mart
construction". Rich would call it part of his.. "ugly amplifier"
scene.
A square of varnished cardboard with two nickels glued to the corners along one edge is light enough to rise automatically with the airflow passing through an 8170. When the amp is off the cardboard flops down, keeping spiders from constructing webs on the insides.
### somebody.. think it was W7RF, radio dan.. supplied curved
plexiglass covers for the henry amps.. to make the exhaust air do
a sweeping right angle... facing the back... this was supposed to
kill some noise.... it would stop dust from settling in.. when not
in use.
A Heath cover is a piece of junk. They paint more of the hole area
closed than have open...
### agreed. Both Heath and Drake woulda been better off to just
made the entire top and sides solid... and 2 x big diam holes..
with fan grilles... right above the tubes.
Heath's SB-220 blows cooling air horizontally and out the left side of the perforated cabinet. Holes above the tubes would do nothing.
### here's the interesting bit. Eimac states the glass tubes
cool by infared radiation.... well my natural gas fireplace puts
out loads of radiant heat.... a 3-500Z doesn't.
So objects that glow red-orange do not exhibit infra-red radiation?
...
R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org
