The AM Forum
December 04, 2024, 07:20:41 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: mounting a 3CX2500F3 - how is that done? it has no 'base'  (Read 17925 times)
0 Members and 1 Guest are viewing this topic.
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8301



WWW
« on: August 07, 2011, 02:32:41 AM »

So there's the question. The 3CX2500F3 has filament and grid leads, and it has no grid flange. How are/were these mounted? By the anode? With those leads, a socket can not be used. I'd appreciate any pictures, links, or manuals that show how the trick is done! Could be educational.


* 3cx2500 pictures.jpg (28.52 KB, 425x491 - viewed 1074 times.)

* 3cx2500F3 drawing.jpg (79.68 KB, 617x800 - viewed 1020 times.)
Logged

Radio Candelstein
N8UH
Contributing
Member
*
Offline Offline

Posts: 194



« Reply #1 on: August 07, 2011, 02:53:54 AM »

The tube simply sits on the chimney. The grid and filament leads connect with lugs. The anode is external of course, so you just use a clamp to attach a lead to it. Quite simple! It is of course necessary to mount the chimney on a pressurized plenum so the tube can get adequate cooling across the base and up through the fins in the anode. I'll send some pics when I get a chance!
Logged

-Tim
Detroit47
Member

Offline Offline

Posts: 663



« Reply #2 on: August 07, 2011, 11:58:52 AM »

I have in the past made a plate with air holes that fits snug around the grid ring. You can clamp it down with that small flange that is on the grid ring. I then mounted the whole thing the chassis using door knob caps as spacers so as to bypass the grid to ground. You can then apply bias to the grid. I did the same thing with a 3CX10000A3. I then adjusted the bias till I had the idling current I was looking for and drove the cathode. There was not as much gain as an A7 but it still puts out good power.


John N8QPC
Logged
kb3ouk
Member

Offline Offline

Posts: 1640

The Voice of Fulton County


« Reply #3 on: August 07, 2011, 06:33:46 PM »

not the exact same tube, but it uses the same mounting arrangement.

http://w2dtc.com/3cx3000f7.htm
Logged

Clarke's Second Law: The only way of discovering the limits of the possible is by venturing a little past them into the impossible
flintstone mop
Contributing
Member
*
Offline Offline

Posts: 5048


« Reply #4 on: August 07, 2011, 08:20:11 PM »

Wow some folks are getting ready for Winter, building flamethrowers..........that will clear the air!!!!!
Logged

Fred KC4MOP
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8301



WWW
« Reply #5 on: August 07, 2011, 10:16:37 PM »

The tube I am considering is an F3, no grid flange. It's interesting, I got the pics, it just sits on the chimney in a little groove. (haha no mobile use!) That amp gives some good pointers though. If I go with this I was considering running grid-driven because it's a low-u tube and takes 150V bias.
Logged

Radio Candelstein
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2690


Making AM GREAT Again!


« Reply #6 on: August 20, 2011, 06:26:50 PM »

You can get a plate made that holds the standard 3000 from the CB community.  Remove the grid ring on the tube, it will mount with three washers.

Matter of fact, you can PROBABLY remove the three collets and socket the tube.  I've found that being the case wtih many Eimac ceramics......

I have a friend with about 45 of the 3000 'socketless' sockets available, let me know if you want one, I'll forward his contact info to you.  I've mounted a 3000 A1 and A7 in them.  Chimney available at Home Cheapo.  Less than 100 dollars for the entire air system assembly for a 3CX3000.

--Shane
KD6VXI
Logged
W7TFO
WTF-OVER in 7 land Dennis
Contributing
Member
*
Offline Offline

Posts: 2496


IN A TRIODE NO ONE CAN HEAR YOUR SCREEN


WWW
« Reply #7 on: August 20, 2011, 06:30:18 PM »

I'd keep the wire leads...no finger stock to crap out or replace. Wink

73DG
Logged

Just pacing the Farady cage...
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13291



« Reply #8 on: August 20, 2011, 08:18:07 PM »

Maybe this will help. The tube is held in there by one set screw and the plate is mounted down with the wires going up to the transformer or terminal block. Too bad the tube in the picture is a dud.


* 100_6895.JPG (1115.27 KB, 2304x1536 - viewed 6346 times.)

* 100_6896.JPG (1167.11 KB, 2304x1536 - viewed 1019 times.)

* 100_6897.JPG (736.89 KB, 2304x1536 - viewed 4577 times.)
Logged

The secrecy of my job prevents me from knowing what I am doing.
W1ATR
Resident HVAC junkie
Member

Offline Offline

Posts: 1130


« Reply #9 on: August 22, 2011, 10:00:12 AM »

Maybe this will help. The tube is held in there by one set screw and the plate is mounted down with the wires going up to the transformer or terminal block. Too bad the tube in the picture is a dud.

There was a company that made sockets like this called Rotron, or Rotran, or something like that. The base seals still need cooling which was normally done by ducting some of the main blowers' air up over the top and back down with a nozzle pointed down at the base of the tube. 
Logged

Don't start nuthin, there won't be nuthin.

Jared W1ATR


Click for radio pix
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13291



« Reply #10 on: August 22, 2011, 10:24:06 AM »

Quote
Quote
There was a company that made sockets like this called Rotron, or Rotran,

I think it was made by Rotron. There are very rare at least on eBay where I purchased this one. I only seen one other and I missed that bid. I think I paid something close to 50 bucks for this one.
Logged

The secrecy of my job prevents me from knowing what I am doing.
k4kyv
Contributing Member
Don
Member

Offline Offline

Posts: 10037



« Reply #11 on: August 22, 2011, 02:23:36 PM »


I have a couple of 3X2500F something. They use glass between the base pins instead of ceramic. Came from an old TV transmitter.  This one uses a socket, and I have two of them.  Also have a couple of filament transformers. One tube would run a cool KW carrie output on AM in leen-yar service. Of course, no idea if the tubes are  still good.
Logged

Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

- - -
This message was typed using the DVORAK keyboard layout.
http://www.mwbrooks.com/dvorak
k4kyv
Contributing Member
Don
Member

Offline Offline

Posts: 10037



« Reply #12 on: August 22, 2011, 02:24:27 PM »

I have a couple of 3X2500F something. They use glass between the base pins and external anode instead of ceramic. Came from an old TV transmitter.  This one uses a socket, and I have two of them.  Also have a couple of filament transformers. One tube would run a cool KW carrier output on AM in leen-yar service. Of course, no idea if the tubes are  still good.
Logged

Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

- - -
This message was typed using the DVORAK keyboard layout.
http://www.mwbrooks.com/dvorak
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13291



« Reply #13 on: August 22, 2011, 04:00:18 PM »

Those were probably 3X2500A3 yubes. More likely the low band part of the TV spectrum just above 6 meters.
Logged

The secrecy of my job prevents me from knowing what I am doing.
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8301



WWW
« Reply #14 on: August 22, 2011, 07:38:46 PM »

.
Logged

Radio Candelstein
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8301



WWW
« Reply #15 on: August 22, 2011, 07:44:21 PM »

Don, those are almost exactly like the 3CX2500's except the plate dissipation is 300W instead of 4000W. The ceramic is probably the difference.

I'm having evil thoughts. Why don't you let me test those things out for you..
Logged

Radio Candelstein
k4kyv
Contributing Member
Don
Member

Offline Offline

Posts: 10037



« Reply #16 on: August 22, 2011, 08:37:07 PM »

According to the old Radio Handbook the dissipation is supposed to be 2500 w.  The filament draws 50 amps. Question is, has it gassed up sitting on the shelf over the years.
Logged

Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

- - -
This message was typed using the DVORAK keyboard layout.
http://www.mwbrooks.com/dvorak
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8301



WWW
« Reply #17 on: August 22, 2011, 09:57:53 PM »

well, maybe it has, but wouldn't it getter the gas by the usual procedure for large tubes?

You are right, I was looking at the 3X3000.

Here's the old 3CX2500 Eimac data.
http://bunkerofdoom.com/tubes/eimac1/image101.jpg
http://bunkerofdoom.com/tubes/eimac1/image102.jpg
http://bunkerofdoom.com/tubes/eimac1/image103.jpg
http://bunkerofdoom.com/tubes/eimac1/image104.jpg

I'm giving up on the multiband 3CX2500F3 idea. The flying leads are a wild card no matter how many ferrite blocks I imagine sliding over the grid wire. Neutralization is another way of saying negative feedback, and I can see how it would be done, and swamping too, but then the drive is 400W peak with a scheme like that assuming always having 2-3x the minimum drive.. GG is out, another thread estimated 1KW driver there.

I do not yet have the knowledge to say that it will work when finished. To build it on the chance I could tame it, - that is a lot of work to do first, and then see if it could actually work. I could end up with a wideband jammer.

If I had in my possession a 10KW FM transmitter, that would be prefect, holes punched, right size tube, everything in place..  hardware development time greatly shortened and getting right down to the RF hackery.

This puts me in a similar place as you Don. I have a 4CX5000A on the shelf, a good pull doing 8KW on FM, and it has not been lit in 10 years. No socket, chassis or the rest of the stuff though.

But I still have evil thoughts about a CCS duty 5-6KW amp. Not because I want the output, but because it will last my lifetime and usually the bigger amp running at 25% power is always cleaner than the smaller one running full tilt.
Logged

Radio Candelstein
W3SLK
Member

Offline Offline

Posts: 2692

Just another member member.


« Reply #18 on: August 22, 2011, 10:34:27 PM »

Those are the type of projects you need to bring to light when its "CQ Corntest, CQ Corntest" season.  Tongue
Logged

Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8301



WWW
« Reply #19 on: August 23, 2011, 01:30:35 AM »

Would the maximum effect be to announce it was completed at that time or just bring the plans to light?
Logged

Radio Candelstein
The Slab Bacon
Member

Offline Offline

Posts: 3929



« Reply #20 on: August 23, 2011, 08:14:17 AM »

Fire that bad boy off and dont say a word, see who notices it.  Grin  Grin  Grin
Logged

"No is not an answer and failure is not an option!"
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8301



WWW
« Reply #21 on: August 23, 2011, 07:29:11 PM »

Hope that does not mean I'd have to participate in the cointest!
Logged

Radio Candelstein
W3SLK
Member

Offline Offline

Posts: 2692

Just another member member.


« Reply #22 on: August 23, 2011, 07:59:17 PM »

Pat said:
Quote
Hope that does not mean I'd have to participate in the cointest!

 Cheesy  Cheesy  Cheesy
Logged

Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
kb3ouk
Member

Offline Offline

Posts: 1640

The Voice of Fulton County


« Reply #23 on: August 23, 2011, 09:06:13 PM »

no you don't have to use it for the contest, but you could fire it up on AM during the contest and see how many contesters notice it when they come on to shoo you off the air because it's contest time and you're taking up one of their precious frequencies.
Logged

Clarke's Second Law: The only way of discovering the limits of the possible is by venturing a little past them into the impossible
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2690


Making AM GREAT Again!


« Reply #24 on: August 29, 2011, 05:08:21 PM »

That grid collet should come right off.  Have a plate made that is the same size as the socket for the grid on a 3000 and you can mount it to that plate.  I use 3 or 4 washers to hold the grid down.  Even in a trailer mounted mobile, no problems 2-3 years later.  You don't NEED the flying grid lead.

ALSO, if you need a chimney, Home Cheapo makes a DANDY for about 8 dollars.  They call them recessed lighting fixtures.  Get the replacement parts kit.  It's a press fit for the tube to slide in.

There.  3CX3000 based amplifiers with no socket, no expensive chimney, and you can still play with the big boys Smiley

--Shane
KD6VXI
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.142 seconds with 19 queries.