--- In ham_amplifiers@..., R L Measures <r@...> wrote:
RICH SEZ... 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.
RICH SEZ... Correct, but Eimac's 0.82" water column spec is the
pressure differential across the socket, and that usually means a
fairly noisy blower.
### The actual spec for a 3-500Z is 13 cfm @ .13" h2o...... or
26 cfm @ .13"... for a pair. And that's for 500/1000 w CCS
anode diss. Now .13" pressure is zip imo. Heck... the
requirements for a SINGLE 3CX-800A7 are 19 cfm @ .5" A 4CX-
250R is 6.4 cfm @ .59" A blower capable of .13" h2o is NOT
noisy. The puny blower in the L4B is dead quiet.. a lot quieter
than the 1" diam tiny fan in my outboard 30 vdc supply for the
yaesu MK-V. [the noise in the mk-v power supply is from the slots in
the cab... not the actual 1" diam fan]
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.
### well, at least you got 2 x nickels to rub together !
### 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.
RICH SEZ... So objects that glow red-orange do not exhibit infra-
red radiation?
### If a 3-500Z is suppose to cool partially via infrared
radiation... I think they are full of it. I can put my hands on the
left side cabinet... [which is flat black... in and out]... and it's
stone cold... and also has zero air on it. You can take the cab
right off... and put ur hand [carefully] on the insides anywhere...
and feel no heat from the infrared radiation. The outsides of the
chimney's are hot [dead cxr, tubes red]... but that's from a lack
of air. The puny blower in the L4B is good for 600W CCS anode
diss... NOT 1kw. The point is.. the infrared radiation is not
heating anything else up in the cabinet. The Fluke 62 IR confirms
this.
### Another point here. The 3CX-800A7 has got 60% MORE anode
diss than a 3-500Z.... but only requires 46% more CFM than a 3-
500Z. So much for..."cooling" by infrared radiation.
### Rich... if you operated the SB-220 at 1500W out RTTY for 1
hr... you wouldn't have enough cooling on the tubes. You would
have to use a real noisy fan. [asuming a real pwr supply, and
loads of air on tank components... like that flaky bandswitch].
The point here is the fan set up in the SB-220 is designed for 600 w
out cw operation [400 w peak anode diss, 200 w CCS].... and 1200 w
pep out on ssb [800 w peak anode diss, maybe 400-500 W CCS]
that's it.... and that asumes you are not TX'ing all the time
either.
Later... Jim VE7RF
...
R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org
