Rework of 3cx3000 input and output circuit

[Crusher]

DXHound,
Thanks for your input as well, and for the most part you make a lot of sense with your point of view. However, what brought me to the decision to at least gut the tank coil, is that, I don't believe it would be able to withstand full steam from the 3cx3000, and although I am able to load up on the lower side of 27mhz, its not centered to enable peak resonance at the desired freq., and as a direct result, lowers the efficiency at desired frequency. The following test results will help you to understand a little better:

With 4.2kvdc with load
50w pep carrier yields 200w and swing 1500w pep with 1.2A plate current
100w pep carrier yields 500w and swing 1750w pep with 1.5A plate current
200w pep carrier yields 750 and swing 2200w pep with 1.75A plate current

note: I did get a little more output - got more with less plate volts and drive, eg., 4kv plate and 45w pep yield 250w and swing 2700w pep with plate current at 1.5A - when I change dooknob from 500pf to 200pf but it almost moved me outside the tuning range of the Pi network...whereas I was only able to load up at the end of C1 and C2.

Now let me give a little background about the rig...its a HomeBrew capable of tuning 10 - 160 mtrs. It has ATI-6 input tuner board on input, on the output C1=0/500pf@15KV, C2=0/800pf@10kv, L1=(10mtrs coil - 0.8uh) B&W 160/850), L2=B&W 802 Choke - 110uH@1A, and 500pf doorknob@15kv

Power supply is a hefty pig that can deliver 5200@2.5A

Now let me make it clear that I don't intend to be running my high performance car like I'm at the Indy, but I would certainly like to be able, if and only, when the occasion warrants, eg. like when you are on the freeway trying to get around a drunken or half asleep 18 wheeler ..to able to step on the accelerator out of dangers way, lol.

Yes, I believe the input is fine...I am able to tune flat for zero reflect, so I 'm good there. The output on the other hand, the plate choke inductance seems bit too high at desired freq, also the max current capability of plate choke is at 1 amp, and will undoubtedly be a problem if the throttle is ever opened. There you have it. What are your thoughts?? I will try to upload some pics later. Again, thanks to all for your assistance.

With the kind of drive you are using, you should see much higher. Amp i had done recently, about 50w carrier in gave me just over 1kw carrier out. Driver was a Pride dx300, swung about 350W pep. Output of 3000 was 6500+ watts pep. Plate @ idle was 5600V and dropped to 5200Vdc. Plate current was just under 1.4A. Grid current maintained below 400mA. Think coil was roughly .72 - .76uH roughly been a little while and didnt write it down. Tube has high anode capacitance, so should take no more than 20-40pf on tune side. Load side in the ballpark of about 250pf roughly. Used a 470pf 20kvdc blocking cap. I think Q was in ballpark of roughly 15 i think.

 

[Duppy Conquerer]

op:op:
Good Morning Fellas,
got in lastnight and saw your responses but was too pooped out to even respond, so I decided to wait til this morning when I'm 100%. I thank each and everyone of you for the out pour of support that you have provided to me, and will forever be grateful. I am very much enlightened and with the guidance provided it has provide a tremendous boost to my confidence to do what I need to do...I can see clearly now that the fog is gone

I have a roll of 1/2" copper tubing on standby that I intend to use to construct the coil...just want to make sure that I get it right the first time around.

so where can I locate the accessories to convert 259B to dip meter? Also, I will be securing a LC meter as well, so these two pieces of test equipment is what I will need to move forward. Trying to shoot for a Q of 12.

I have taken some pics this morning so you guys can see what I'm talking about.
Oops! When I tried uploading from my computer system indicated that my files exceeded the 640x640 limit and that I would have to resize, then I tried using the URL upload feature but still got an error message of invalid file:

http://s758.photobucket.com/albums/xx221/Boneman_Album2/Web Store Listings 2012/:
Invalid File

So, I am just gonna post the link as it is to view album here:

Web Store Listings 2012 pictures by Boneman_Album2 - Photobucket

 

[Crusher]

Nice little amp. Wish chimney a bit tighter around tube. If your gonna put a maul out there, you better make sure air flowing thru tube. not around.

 

[Duppy Conquerer]

You are absolute right...the blower is pretty strong and it appears that some of the airflow flows up and mostly around the tube...I will have to modify the chimney, seems like I'm gonna have to devise a way to seal up the approximate 1/8 of an inch space around tube to allow direct airflow through the tube.

 

[dxhound]

Also,Might wanna relocate a few componets away from the inductors. There should be nothing metallic within 1/2 the diameter of the coil. Just a rule of thumb to help keep down on stray mutual inductance. At certain power levels you might see a change of inductance do to coupling with those metalic objects. Also, clean off the flux on all connections, it will cause corrosion of the metal.

Looks like a nice little amp, Very compact. If you really want to have some fun, try adding switchable biasing and run that monster in class A too. 20% efficient, but the quality is incredible!!

 

[Captain Kilowatt]

Nice little amp. Wish chimney a bit tighter around tube. If your gonna put a maul out there, you better make sure air flowing thru tube. not around.

Oh God yes. Those chimneys should just barely fit around the tube anode. The air should be forced thru the tube fins and not around them.

 

[Crusher]

Very good point on location and spacing Dxhound. With as close as some of those inductors are, could see some added inductive coupling. Also if coils get to close to sides of case or to close to capacitors weird stuff starts to happen. I like my stuff more open, not as compact, but helps alleviate some of the gremlins in hiding. I like the input tuning board. Nice, neat and laid out practically. Some guys will use a small bead of silicone between chimney and tube. This will seal up gap. Or you might find a thin sheet of teflon or some rubber silicone sheeting that you can put around. Maybe I'm going overboard, but I like the tube to get max airflow thru to keep temp down. A 3000 tube aint getting any cheaper. Plus I like overkill. When it comes to heat and RF. Can't really go overkill in the components department. The weakest link goes first or will tell you there is a problem.

 

[Duppy Conquerer]

Wavrider,
Thank you very much for your input, you guys are great! Keep up the good work.
73

 

[wavrider]

mfj has on online catalog for the accessories your welcome for info many members here enjoy building/repairing amps. almost a lost part of the hobby glad to see some still are active in that part of the hobby.

 

[Crusher]

Not an amateur operator, just a radio hobbyist that likes to dig deeper and understand some of the theory behind it all. Maybe someday. Honestly I have more fun working on the stuff.

 

[Duppy Conquerer]

Thanks I will look into it. Have a Bless Sunday. I'll keep you all posted.
73

 

[Crusher]

How many meters on the amp anyways? Looks like 2 from what I saw. Probably HV meter and maybe Plate current meter. Unless it has a switch so second meter can be used for various applications. Be nice to monitor grid current. I think 500mA is what 3000 is safely rated for. But I know it gets pushed farther than that by many. Can't wait till you get LC meter and start working on it.

 

[Duppy Conquerer]

Crusher, it has 2 meters on the rf deck, one for plate current and the other is filament voltage. Yes, I may put grid meter on it, good to monitor all aspects of operation. Also, I do anticipate a great deal of fun reworking the rig. I will try to get LC meter soon, will keep you posted.
73