[AMRadio] My Amplifer Quest took a strange turn today


Bow kd5kzn at sbcglobal.net
Mon Apr 23 03:39:12 EDT 2007


 Well, A bit of an update on my new toy..

I tested it today, after repairing some solder joints that were not up to my
specs and replacing some wire I didn't like that looks of.

The test was:
Icom IC-718 --> MFJ-949E antenna tuner-->Amplifier-->Daiwa 3kw watt
meter-->MFJ legal limit dummy load.

The IC-718 will do 100 Watts on CW/SSB/Rtty and 40 watts on AM

I used the frequency of 3870 kHz

I first used a RTTY signal 
Input from Rig - Output from Amp - Grid Current (amps) - Plate Current
(amps)
30 - 180 - .02 - .24
50 - 380 - .07 - .34
60 - 400 - 0.1 - .36
75 - 410 - 0.2 - 0.4

Next I tried an unmodulated AM carrier

25 - 200 - .04 - .26
40 - 375 - 0.1 - .34

Final Check was on SSB, modulated to the peak ALC setting with a 1 kHz tone.
30 - 110 - .02 - .16
40 - 200 - .02 - .18
50 - 210 - .02 - .22
60 - 300 - .04 - .22
70 - 375 - .04 - .24
80 - 400 - .06 - .26

I figured 80 watts was about as hard as I want to drive it.
I don't have a High Voltage test lead here to actually check the plate
voltage, but I am going to take this featherweight (NOT!!!) into work with
me and check it out there.

Here are some more photos, including the guts. I may just rewire this thing
for my own piece of mind.

http://riley-music.com/BowsStuff/AMP/14Guts.JPG

http://riley-music.com/BowsStuff/AMP/15TubeSockets.JPG

http://riley-music.com/BowsStuff/AMP/16Relay.JPG

http://riley-music.com/BowsStuff/AMP/17PWRSection.JPG

http://riley-music.com/BowsStuff/AMP/18MeterSwitch.JPG

http://riley-music.com/BowsStuff/AMP/19CapChoke.JPG

http://riley-music.com/BowsStuff/AMP/20FilTranny.JPG

http://riley-music.com/BowsStuff/AMP/21PWRTranny.JPG

http://riley-music.com/BowsStuff/AMP/22CoilSwch.JPG

I guess now I need to figure out how to do a few things.... Get an opinion
from someone who knows something about amplifiers and homebrewing....
1. Make it band switch able for 80/40/20/10
2. Figure out a tuned input for the above bands
3. figure out how to get it up to a 600 watt output level (because everyone
tells me the first 600 watts are the best for signal boost)


Bow

W5EFR


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