Building a new amplifier

[Opcom]

That closet is going to be warm in the winter and a great place for drying fruits and making jerky in the summer. How will the waste heat be dealt with?

[ka1tdq]

I had to use an RF attenuator in line between my transmitter and my old dual 3-500 linear.  My transmitter puts out about 22 watts carrier, and I had to do that in order to give me some headroom.  Now with the three tubes, I should just be able to drive it directly and not have to worry about headroom. 

I'll mount the LDG tuner directly at the input to the amp. 

Heat in the closet could be a problem.  I'm definitely going to keep the door open during operation.  I chose the closet to keep my radio room neat and to keep my little ones locked away from high voltage.  The closet is a good size, but if keeping the door open isn't enough I'll put a fan on the shelf to blow the heat out.  The intake for amp blower is on the bottom of the floor. 

Jon

[ka1tdq]

I just ordered the tubes and I bought the RF Parts brand 3-500.  They come with the 3 year warranty rather than the 2. 

I have one last concern though:

My plate caps were machined to fit directly on the plate pin.  Is the plate piece you see in the picture removable on the RF Parts brand tube?  It looks like there's a set screw in some pictures.  It would really suck if my plate caps wouldn't fit. 

Jon

[KD6VXI]

I forgot  size,  Jon,  but yes.   A teensie weensie (I believe that's the military term)  hex wrench will expose the anode pin.

I've never checked the Chinese tubes for pin size though.   

Show off your seckzi anode caps!

--Shane
KD6VXI

[ka1tdq]

How's this for sexy?  I'll install them when the tubes arrive.  I want to mount them as best I can to eliminate mechanical stress on the tube, so I'm patiently waiting.

The tubes should be here Wednesday or Thursday, and then I need the assistance of my lovely wife for tuning up.  Transmit switch in one room... amp in the other. 

Jon

[K5IIA]

my plate caps would not go on, very close to fit but just would not go all the way on. I clamped the in a vise, one at the time and drilled the out one size up. Just make the hole a c hair bigger and fit perfect.

[W8VG]

Jon, what a neat looking project!!!!!!  Way Cool! 

The Chinese sockets/chimney's and Ruskie vacuum variable w/mounts are pretty dawggoned sweet!!!!

Can't wait to hear it strappin down into Tucson on 7293 in the mornings!

Best 73's
Geo W8VG
Oro Valley, AZ

[ka1tdq]

Hey George! Yeah, I'm hoping to put out some serious power soon. Tubes arrive tomorrow, and then whenever I can fit in time for testing. Work gets in the way...

Jon

[ka1tdq]

...and power!  I'm getting about 365 watts carrier.  Had great audio and signal reports from Tucson, Los Angeles and Las Vegas.

https://www.youtube.com/watch?v=Ns7FshDPrSs

Jon

[Steve - K4HX]

NICE! Triple threat.

[KD6VXI]

Maybe I'll hear ya now Jon....   Lol.

--Shane
KD6VXI

[ka1tdq]

Ha!  Yeah.  I've heard you on 40 a couple times, but did't try to talk because you probably wouldn't have heard my little 22 watt transmitter. 

Here's a little YouTube video that my wife shot while I was transmitting.  You can see the linear in all it's glory.

https://www.youtube.com/watch?v=e85oJAjfVkU

Jon

[Ralph W3GL]

Just make the hole a c hair bigger and fit perfect.

The correct term for that modification is an "RCH"... 

   

[W6TOM]

  Very nice amp !! What 40 meter net?? Wonder if you would hear the Bay Area??

[KD6VXI]

Just make the hole a c hair bigger and fit perfect.

The correct term for that modification is an "RCH"... 

   

This neck of the woods,  we prefer them blonde lol

Or,  nonexistent!

--Shane
KD6VXI

[Opcom]

With that amp, maybe we could hear you in TX on the Sunday 7160 AM round table, vaguely from 11AM to 1PM Central.

[ka1tdq]

I'm going to Vegas next Sunday, so I'll listen out the following week.  "Viva Las Vegas, baby." (In my best Elvis voice).

Jon

[KB2WIG]

Wow. I'd never figure girls like that  are on 6m AM!

klc

[Opcom]

They are all standing in front of a giant 3CX3000.

[N4RMT]

This is remarkable!  Great build and great thread.  I enjoyed the ride.

[Opcom]

That's true.  A pair of 3-500s has a nice 50 ohm impedance match, but three don't.  I'm going to use an LDG auto tuner in line before the amp. 

Jon

This is grounded grid, but it think I'll throw in that trying that with a low drive high power class C stage can make the meters go as crazy as an outhouse rat until it stops. If it stops.