Hi,
Thanks very much for all the kind words and comments!
It is very exciting to have this critter actually work, w/o drama involving a fire extinguisher.
Lots of the parts came from the local surplus place
http://www.skycraftsurplus.com/Highly recommend visiting if you are in town for the Orlando Hamfest or Dizzy world, etc.
Most of the ideas were from
http://w2dtc.com/3cx3000f7.htmSubsequently modified with input from my Elmer, Joe Lang, and N2ZAB.
I'm just the Chimp with the soldering iron, milling machine and TIG welder, following instructions.
In the 1950's I was in the Orlando Electronics Club, and in later decades, returned to RF electronics (industrial).
But time and brain cells fade away, and so I had to pick up and start over with I=E/R again.
Blower is a three phase Rotron Centrimax.
Used a VFD (Variable Frequency Drive) to operate it on single phase power.
Here is the current state of the interior of the cabinet:
The filament choke was about 4uH as delivered.
I stuffed it full of type 43 rods, hoping to use this amp on 160M someday. Close to 30uH now.
The plate has three taps on the secondary, we started with the "2600".
Unfortunately, the other two taps are are "no way" and "ludicrous".
This transformer was all I could obtain at the time, would have been better if there was something in the 3k range.
I will try the next tap later (Hey, 1KW carrier is not enough for you guys???).
It will be necessary to do some minor mods to maintain the critical value of inductance w/o changing the choke any more.
(Can't fit more than 20H in there)
Resonating the chokes might be in the plan if I can't get the numbers right, trying the simple way first.
So the only other easy variable to modify is the bleeder current.
The bleeders operate at about 120 degrees now, at a small amount of bleeder of current.
For the next tap 2600-->4000 (I have not done the calculations), might need over 500 mills, so fans will be needed for the bleeders.
They won't melt until about 700 degrees;)
(It's hot enough in the shack with this thing now....)
The tank is some Collins commercial thing from the 1940's.
(Even older than me)
VERY well made, all on ceramic standoffs, not worried about breakdown.
These are the windings it really likes for 75M
The weak link is the oil caps, rated @ 5kv.
But if I can keep the critical value of inductance in line, there won't be any weird voltage spikes, so that might work
OK @ the next tap on the plate transformer.
Thanks for the advice on the glitch fuse, I'll fix it. The gray shape is the fan housing (plastic).
Also need to add the PTT & bias parts of this circuit from w2dtc, so as to cutoff the PA.
http://w2dtc.com/w2dtc-3cx3000f7/2011-0811-schematic-cathode.jpgI'm looking forward to retiring next year so I can concentrate on even more fun projects!
73
Frank
KJ4OLL