[Amps] 12 tube 3-500Z

[Phil Clements]

> That 12 holer on ebay using (12) 3-500Z's is a piece of work aint
it?
> You would need at least 1 Kw to drive the thing where no standard
radio
> could ever drive it. Although, it is possible to do this, I seen
several
> flaws to this amp. First is the cooling as I only caught  5 muffin
fans
> on the top, and what looked like 3 more blowing in at the bottom. I
> believe it were me, I would have used a couple of large blowers in
the
> bottom, then chimneys around the tubes. We all know the heat these
> things create, especially around the tube pins at the bottom. Next,
if
> this is what I was seeing, the filament transformer was in the
bottom?
> If it was it, it kinda looked awful small to me! It about had to be
it
> as the leads for the filaments choke was tied directly to it. Third,
I
> never noticed hardly any bypass capacitors in the bottom of this
beast.
> Forth, you can notice in the top that it was used in high frequency
only
> with no band switch. Last, the plate choke looks awful small to me
too!
> I think I'm just bad to knit-pick. Anyhow, it was an attempt wasn't
> it........


This has been covered in the past, but there are a lot of questions
and comments from
USA and DX folk about these "unique" amps as they show up on E-Bay
from time to time.

Here is how they are used:
There are Sunday afternoon "Shootouts" occurring all over the country.
There are several classes, thus the choice of tubes determines what
class you compete in,
and how much power supply you have available. The entire lash-up must
be mobile, but trailers
are allowed. Rich is correct, the "gammer" match is for coupling the
RF to a metal pole or whip
mounted on the vehicle. Getting an antenna system that won't melt is
sometimes quite a chore!
The blowers on the E-Bay amp are okay in this case, because you only
key down for a few seconds
when it is your turn to compete. There is never any modulation
involved...just a key-down dead carrier
for long enough for the judges to get their readings.

What drives these people to invest all that money and effort, you ask?
Tens of thousands of dollars in prize money and side-bets change hands
in one afternoon!

Do not confuse these "Shootout" amps with something a CB'er would put
on 11m and talking on it,
or a ham using it on 10 m. They are keyed up maybe 10 minutes total
per week; a few seconds at a time.

I do not pass judgment on these "hobbyists". They probably thin I am
weird because I invest a lot of
money into ham radio with no hope of  profit!

(((73)))
Phil, K5PC