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Author Topic: 3cx3000f7  (Read 16524 times)
KK4RSV
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Posts: 78




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« on: July 09, 2015, 01:06:27 PM »

I am thinking about building a 3cx3000f7 amp for 10-160. Thoughts? Opinions?  Heartburn?
bahahaha
KK4RSv Grin
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WB2WIK
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Posts: 21837




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« Reply #1 on: July 09, 2015, 01:31:36 PM »

If you already have the tube, use it.

But with the flexible leads instead of a socket, I'd expect problems in RF amplifier service much above MF.

3CX3000A7 sockets aren't difficult to come by.  Amplifier Systems Inc., a couple of miles from me, uses 3CX3000A7s all over the place and has lots of sockets. Wink

http://www.ampsystems.com/asiprod-old.htm

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N8CBX
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Posts: 565




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« Reply #2 on: July 09, 2015, 03:48:01 PM »

About 400W just to light the filaments.
Jan N8CBX
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Dayton Ohio - The Birthplace of Aviation
W8JX
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Posts: 13268




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« Reply #3 on: July 09, 2015, 04:41:35 PM »

What ever happened to legal limit. No way you build with a tube like that for just head room. Seen a lot of change in 46 years in hobby and some not for better. Pretty soon there will be no license requirement and power limited only by pocket book the way things are going.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
VR2AX
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Posts: 1016




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« Reply #4 on: July 09, 2015, 05:07:03 PM »

The version with a base is very popular in Japan as well.

http://www.bear-el.com/3000prisepa/

http://www.bear-el.com/3000kihon/

A single one covering 10-160 well might be a challenge. 80-10 or 40-10 maybe more realistic.
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KM1H
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Posts: 5550




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« Reply #5 on: July 09, 2015, 05:10:51 PM »

Its no different now then it was decades and longer ago. Pulls from BC, FM, and TV were readily available and lots of amps were being built. I did several 1 and 2 tube 4-1000A amps and a couple of 3CX3000A7's, kept me out of the bars at night and helped to pay for toys.

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KK4RSV
Member

Posts: 78




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« Reply #6 on: July 09, 2015, 06:42:54 PM »

What ever happened to legal limit. No way you build with a tube like that for just head room. Seen a lot of change in 46 years in hobby and some not for better. Pretty soon there will be no license requirement and power limited only by pocket book the way things are going.


Mr. W8JX I assure you there is no intention of running greater that legal limit. I follow the rules and I see no point in it. however one of the things about this "HOBBY" that has always interested me is the ability to build some of your own equipment. There's nothing wrong with running an amplifier at legal limit even if it has the ability to produce much more. Under you viewpoint cars should be built to only run the maximum speed limit. But you do have the right of your opinion and I did ask for it. Thanks for your input.
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KU3X
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Posts: 623




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« Reply #7 on: July 10, 2015, 04:14:41 AM »

Clinton.....OOPS ! Darrell, This may or may not apply since I don't know you background.
If you build your amp, or any amp, I highly suggest you read at least two good books.
1. Bill Orr's Radio Handbook
2. ARRL's Handbook

Building a power supply, whether it's just a regulated 13.8 volt 20 amp power supply or a 4KV power supply, it's pretty much point to point wiring. But when it
comes to building an amp, it's much more then just connecting the wires.

Stray capacitance, stray inductance and lethal voltages are just a few things you must understand.
Maybe this is all moot and you have a good background, but if you don’t....be careful !
Barry
« Last Edit: July 10, 2015, 11:06:55 AM by KU3X » Logged
G3RZP
Member

Posts: 1321




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« Reply #8 on: July 10, 2015, 05:24:44 AM »

Needs a biggish blower and I suspect, inrush protection for the filament. At 4kV,  that's 1 kW of plate dissipation and 400 watts of filament, so you won't need room heater in winter, but I suspect you'll really need A/C in summer!
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W3RSW
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Posts: 606




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« Reply #9 on: July 10, 2015, 06:40:44 AM »

Heat energy if properly utilized can actually provide cooling in another separate insulated space, say a food refrigerator or room, e.g., natural gas or propane fired refrigerators and air conditioners. The trick is to dump even more heat outside or across a thermally insulated barrier, the working energy plus the heat from your tube in this case. 

A decent ham ought to be gifted enough to build such.  Grin

There is formal thermodynamic nomenclature for such, iso-this and that, throttling valves, heat transfer, etc.

In the case of a 3cx1000a it's even simpler than building an adiabatic air conditioner. Simply pipe the discharge air outside the house. Usually the house walls provide sufficient insulation to keep the heat out. Pipe your input air from the other, windward side of the house. Grin
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Rick, W3RSW
NJ1K
Member

Posts: 3




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« Reply #10 on: July 10, 2015, 08:15:35 AM »

Heat energy if properly utilized can actually provide cooling in another separate insulated space, say a food refrigerator or room, e.g., natural gas or propane fired refrigerators and air conditioners. The trick is to dump even more heat outside or across a thermally insulated barrier, the working energy plus the heat from your tube in this case. 

A decent ham ought to be gifted enough to build such.  Grin

There is formal thermodynamic nomenclature for such, iso-this and that, throttling valves, heat transfer, etc.

In the case of a 3cx1000a it's even simpler than building an adiabatic air conditioner. Simply pipe the discharge air outside the house. Usually the house walls provide sufficient insulation to keep the heat out. Pipe your input air from the other, windward side of the house. Grin

I hope your post was only in jest.  There are lots of reasons why it would not be feasible to provide a refrigerating effect from the waste heat from a ham amp.

Further, while discharging the waste heat outdoors is a fine approach, bringing unconditioned outdoor air into your amplifier brings a whole host of nasties with it including high summertime humidity that would love to condense on the cold internal amp parts during the warm-up period.  And, assuming your ham shack is air conditioned, when the amp is off, the humidity will migrate through the intake duct and right into the cool amp and "rain on your parade".

Of course, I'M sure it was only in jest.
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G3RZP
Member

Posts: 1321




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« Reply #11 on: July 10, 2015, 08:39:37 AM »

I know that in some portable contests over here on VHF, especially about late August and early September when the various bugs are out in force, amplifiers with 4CX250Bs and the like at 2kV have produced some spectacular fireworks when the bugs get through the blower.......
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NJ1K
Member

Posts: 3




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« Reply #12 on: July 10, 2015, 08:46:12 AM »

Well, I do have first hand experience with cooling from outdoor source.  I built a mini air handler complete with filtering, static pressure ports, and air-flow interlock.  It all worked marvelously except that during the summer months when the amp was not in use, moisture would condense inside from migration through the intake duct.  when the amp was first fired up, often time, WAMMO!!!!, HV arc. 

So, I now cool with the remote air handler but it's inside the house in another room.
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KK4RSV
Member

Posts: 78




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« Reply #13 on: July 10, 2015, 09:34:56 AM »

Clinton, This may or may not apply since I don't know you background.
If you build your amp, or any amp, I highly suggest you read at least two good books.
1. Bill Orr's Radio Handbook
2. ARRL's Handbook

Building a power supply, whether it's just a regulated 13.8 volt 20 amp power supply or a 4KV power supply, it's pretty much point to point wiring. But when it
comes to building an amp, it's much more then just connecting the wires.

Stray capacitance, stray inductance and lethal voltages are just a few things you must understand.
Maybe this is all moot and you have a good background, but if you don’t....be careful !
Barry
Barry i am not sure if you are addressing me. My name is Darrell. Anyway, I have read both of those books and the 1961 and 1964. Amatuer Radio hand  books as well. I have built many amplifiers and just finished a 2x 3-500z with 3800 vdc plate for 10-160. I have had many classes in electrical and electronics and spent almost 30 years in Industry as a mechanical and electrical/electronic trouble shooter. I spent approx 6 years in different schools and classes learning the disciplines.
Thanks for your concerns and comment.
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KU3X
Member

Posts: 623




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« Reply #14 on: July 10, 2015, 11:05:16 AM »


[/quote]
Barry i am not sure if you are addressing me.
Thanks for your concerns and comment.

[/quote]

Yes, I was addressing you. Sorry I put down the wrong name. So glad you are up on working with HV and RF.  I've had so many people visit here, see my home brew amps and then they say they are going to build one. Once I tell them what's involved they give  me a look like, "A deer in headlights."
I hope you go ahead with your project and wish you very good luck.
Barry, KU3X
www.ku3x.net
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