--- In ham_amplifiers@..., "Peter Voelpel" <df3kv@...>
wrote:
Hi Jim,
I use heatresistant glass cylinders I get made locally and also
use
round teflon covers as you, thats works very well.
All my blowers are made by EBM.
I do not like to boost a tubes rating, I rather prefer then to use
a
bigger one.
I prefer that my GG amps cannot run in too high dissipation at
full
drive. They should have no problem when the antenna gets lost...
### Partially agreed. ..BUT the 3CX-6000A7 is rated at 3.5 A
of plate current CCS. [7 kv under load] .
## as is.... with 2.5 A of plate current @ aprx 6900 V under
load.... DC input is 17.25 kw....... output is 11.5 kw. Anode
diss is 5.75 kw. At 6kw of anode diss.... lower anode
seal [ where the anode meets the ceramic] will be 225 Deg
C !
### I don't like running tubes anywhere near their max
anode diss. The saving grace here is ssb/cw............ the
duty cycle is WAY down. Plus Eimac's air flow specs are
based on a 50 deg C [121 deg F] intake temp... which it's not.
### The point here is.... one would HAVE to increase the anode
diss with more airflow.... in order to operate with 3 - 3.5 A
of plate current.
### Eimac also makes an industrial heater tube.... 3CX-10,000D
with a real small anode... 6.4" diam. I phoned em up.....
they just blew more air through it to get the 10 kw anode diss !
### also note the Eimac 3CX-10,000A7 and also the 3CX-15,000A7
have IDENTICAL physical dimensions in every regard.
What's the diff ??? They just blow more air through the 15K...
that's it.
### Both the 3CX-2500 and the 3CX-3000A7 have IDENTICAL
dimensions/weights. BOTH are rated at 4000 watts of anode
diss... CCS ! Eimac tells me the 2500 was origionally
2.5 kw anode diss.... then they upped the airflow....... ditto
with the 3000A7.
### The 6000A7 is one of the easiset to cool [ and to increase
the anode diss if needed/wanted] . Reason is.... the ceramic
stem is real small diam compared to a YC-156.. 10K, 5K. With
it's 6.125" OD cooler..... you end up with a HUGE fin area
underneath.
## To really utilize this huge fin area underneath... it's gotta
be able to breath right........... and that means the AREA of
the holes /slots in the chassis should be at least the same or
bigger, than the underneath fin AREA. And that means NO
straight up/down chimneys can be used......... hence the 9"
square box we used.
### The Eimac 10,000 chimney is a virtual straight up and down
affair.... and chokes off the airflow from the chassis.
### When I see a 5 HP... 3 phase 208V blower motor for a
pair of 3CX-15,000A7'S...... it makes me gag.
### Compare the pressure requirements of a YC-156 [or a 4CX-
5000] vs a 3CX-6000A7... you will get the idea. [compare em at
the SAME 50 deg C inlet air temp]
Jim VE7RF
73
Peter
--- In ham_amplifiers@..., "pentalab" <jim.thomson@>
wrote:
For an experiment, I remember W7IUV had fabricated a
fiberglass
box around his YC-156.. for a chimney.
We tried the same trick... except the vertical sidewalls
were
made from wood... about 9" square... top was also made
from
wood.... and the original chimney was placed in a groove..
on
top of this wooden affair. Now we could increase the
hole
sizes on the chassis.
The result was a huge improvement! Intead of the original
205
cfm... we are now getting an easy 320 cfm [using a
Dayton
5C508 dual speed, capacitor start blower].
