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It's Alive!




 
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KD6VXI
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« on: June 11, 2018, 12:27:59 AM »

Newest project I'm throwing together.

Power supply is 7.5kv low, 9.5kv hi tap :-)

Stepstart on the filament supply separate from the power supply.

Thought I'd show a few pics.  Should have taken a lot more, but....

--Shane
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ka1tdq
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« Reply #1 on: June 11, 2018, 12:57:57 AM »

I like it, a lot!  My only problem is that I don't have 3 phase to run something like that.  Are those 4-1000's?  The B+ you talked about would be a little high, so I'm wondering.

Jon
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KD6VXI
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« Reply #2 on: June 11, 2018, 01:24:19 AM »

Jon,

Yes they are.   With the quality of 4-1000s around, a little higher voltage can really help.  That and a variac on the filament to bump it a bit higher.  Turns those old brown bottles new again!

That, and it's what I could come up with. I've got this transformer and a couple 3kv supplies.  3kv barely makes a kw with the pulls I've come across.  4.5 really wakes them up....  😎

Should it prove to be too much to tame, I do have a choke I can throw in, but it would have to be on a shelf, the floor of the power supply is filled already.

Lots if bias to keep zsac down. Also, I chassis punch the same size as the tube ring.  The tube ring pops into the chassis.  Makes an air tight seal and helps with stability at the anode voltage.

Only takes a 60 amp single phase breaker :-)

Meter scale hasn't been drawn yet, but it's 10kv full scale.  20x4700uF caps on the cutting board.  Each one has a 200k 2 Watt and a 10A10 diode across it.

--Shane
KD6VXI


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steve_qix
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« Reply #3 on: June 11, 2018, 07:32:31 AM »

I looked at the pics, and saw the power supply voltage and thought "how is he going to modulate that" ?  Then taking a look under the chassis, I realized it's a linear.  Yes, the higher voltage will DEFINITELY be an asset, particularly with old tubes  Cool

Even with modulated tubes, I always ran absolutely as much voltage as possible (for instance, 4000VDC on 450TLs, 3200V on 304-TLs, etc).  Efficiency was improved, and you could get a lot more power than otherwise available at lower voltages.
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KD6VXI
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« Reply #4 on: June 11, 2018, 09:59:27 AM »

I'ma pwm the primary Steve!  Lol


--Shane
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WBear2GCR
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« Reply #5 on: June 11, 2018, 03:13:34 PM »

Shane...

I'd probably want to vibration isolate that blower.
Maybe it's nothing, but I think filament/grid vibration is not a good thing.

                           _-_-
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« Reply #6 on: June 11, 2018, 06:56:21 PM »

Shane...

I'd probably want to vibration isolate that blower.
Maybe it's nothing, but I think filament/grid vibration is not a good thing.

                           _-_-
pushing things that much every little thing may help.
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K1JJ
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« Reply #7 on: June 11, 2018, 07:12:24 PM »

Hi Shane -

Nice project. I've always liked 4X1s in linear or class C.

Some comments to help out:  

Voltage:  5.5 KV is about the best voltage for linear service - best plate rating match and cleanliness. Go higher and you will start generating X-rays.   In addition electron  "bounce" can cause forms of non-linear performance.

The other issue is plate dissipation.    When running over 6KV, if you idle the tubes for reasonable current, they will start approaching their plate ratings.  With 7-9 KV, they are near their rating on key up and when talking the plates may turn white... :-)

Sure, you can run them higher than 5.5 KV, in fact some guys will plate modulate with 6 KV = 12-14KV peak on the plate, but the cleanest and most reasonable choice for linear class service is about 5.5 KV.

BTW, are those the filament chokes with the single cores? If so, I'm not sure you will have enough inductance for 75/160M or if so, they may saturate.  Also, axe Frank/ WA1GFZ about his hum problems with his 4X1 when he ran them separate like that. A bifilar wound choke with 8 of those cores may be a better choice. That's what I use in my own pair of 4X1s in linear. With a long stack of cores, only one pass thru of filament wire is required.

Just take 50 ohms input * 10 = 500 ohms.  Measure the choke for the lowest band used to have an inductive reactance of at least 500 ohms.  It should be as easy to drive on 40 M as 160M - then you know you have enough inductance.   Also, be sure to add the input tuning for best IMD.

T

This is my 4X1 pair linear. It is GG, but AB1, no grid current.   It uses electronically regulated 500V screens and rock solid grid biasing, 4.5 KV plate -  for that clean sound....  (not to be confused with Fabio, the 4X1 plate modulated rig)   I am looking for the fil choke pic to post.


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« Reply #8 on: June 11, 2018, 08:45:30 PM »

I used the smaller brother of he 4-1000, the 4-400P in pulsemode. Did pulse 5 - 7 kW output with 10 kV at the anode at 13.56 MHz. That was for a dielectric barrier pulsed plasma generator.
Very nice tubes, 5+kW out with 6 Watts drive.
I think that the only difference between the pulse version and the A version is the vacuum, which is guaranteed better than ....
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PA0NVD
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« Reply #9 on: June 11, 2018, 09:11:39 PM »

If the anode voltage is a problem for the 4-1000, the 4PR1000 can handle upto 15 kV and has very similar RF data. See datasheet


* 4PR1000.PNG (121.72 KB, 738x531 - viewed 19 times.)
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K1JJ
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« Reply #10 on: June 11, 2018, 09:20:12 PM »

Yes, the 4PR-1000A is the same tube, but the elements are "blueprinted" -  IE, the spacing and alignment tolerances are closer to spec. A lot more work than just slapping them together on a factory jig. Labor intensive.  This allows higher voltages reducing the chance of arcing due to misaligment.  For example, if the screen is slightly leaning in respect to the plate, etc. We have all seen tubes with misaligned structures... I've seen my share when I look closely. I have a few 4PRs here and use them in RF service.

Interesting on the better vacuum.  I've not heard that but it makes sense.

T
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“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
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« Reply #11 on: June 11, 2018, 10:57:35 PM »

Beside the better alignment and vacuum, the electrodes are also made of an other very low emission material. Nice tubes and they are still available.
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KF7WWW
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« Reply #12 on: June 12, 2018, 09:25:03 AM »

There is also the 8960 variant..
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PA0NVD
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« Reply #13 on: June 12, 2018, 09:49:02 AM »

I didn't know that one, seems quite a bit more powerful. You ever used it?
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Detroit47
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« Reply #14 on: June 12, 2018, 04:47:15 PM »

Hey Shane that box reminds me of Clarence Crack Carter. He had six of dem big legged girls. He had a name for every one of them. I have some of those Corning 10 watt 56 ohm glass resistors for parasitic suppressors. You are welcome to some if you want.

73 John N8QPC
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KD6VXI
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« Reply #15 on: June 12, 2018, 07:10:29 PM »

Bear, ultimately, it will be grommet mounted and then I use some rtv to seal.

Tom, I was under the impression x rays where a >10 kv thing.  This will normally be run on the 7.5kv tap, which is still pretty hot.   The other taps are their, well....  Because that's the transformer I got.

It's currently on 20 meters, but as soon as I hit a few hundred watts, my home alarm went off.  Nevermind it's not even turned on, was sitting in the 'off / home' mode!  Yes, quite disconcerting! Guess I need the antenna up in the air a bit more!

I've used the PR series tubes before.  Usually no difference in what we use them for.  I wonder how much the better alignment effects imd?

--Shane
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KD6VXI
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« Reply #16 on: June 12, 2018, 07:11:57 PM »

Lol.  I like Clarence.  He's a character.

I'll take you up on the resistors if it proves necessary.  Definitely gonna have a hv fuse and surge R in this one!

--Shane
KD6VXI
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KH6KK
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« Reply #17 on: June 12, 2018, 09:08:58 PM »

Yes, the 4PR-1000A is the same tube, but the elements are "blueprinted" -  IE, the spacing and alignment tolerances are closer to spec. A lot more work than just slapping them together on a factory jig. Labor intensive.  This allows higher voltages reducing the chance of arcing due to misaligment.  For example, if the screen is slightly leaning in respect to the plate, etc. We have all seen tubes with misaligned structures... I've seen my share when I look closely. I have a few 4PRs here and use them in RF service.

Interesting on the better vacuum.  I've not heard that but it makes sense.

T

Hi, Interesting to read as I have an Eimac 4PR1000A that has a slightly tilted anode, looks straight from one angle, but off from other angles. Just a slight amount only. I guess it got bumped in shipping.. Lights up fine, and no measurable shorts but never tried applying HV to it thinking it was damaged. Your post gives me hope and I think I'll try it next time. Thanks!  Cool
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K1JJ
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« Reply #18 on: June 12, 2018, 10:28:40 PM »

I wonder how much the better alignment effects imd?
--Shane
KD6VXI

I don't think we are talking about enough misalignment to affect the transfer curve linearity much.  Though, I'll bet if a grid or screen had a hole blown in it, the IMD level deterioration could be easily measured... :-)


BTW, here's a picture of the filament choke I used.  I ran out of room underneath the 4X1s' sub-chassis  and didn't want to restrict air flow, so mounted them outboard but added shielding later on.

The whole thread is here:
http://amfone.net/Amforum/index.php?topic=34543.0

Where do we get the time and motivation to build these rigs?

T


* 4X1 Linear 1.JPG (320.91 KB, 1280x960 - viewed 49 times.)

* Linear 2.JPG (322.92 KB, 960x1280 - viewed 48 times.)

* Rico Suave 2.JPG (329.67 KB, 960x1280 - viewed 52 times.)
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“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
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« Reply #19 on: June 13, 2018, 09:41:38 AM »

I didn't know that one, seems quite a bit more powerful. You ever used it?

I have one that is down on emission, so I can’t give you accurate results.. I do know that it seems to run better with more HV..
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« Reply #20 on: June 13, 2018, 10:59:05 AM »

Tom Vu,

Looking at your pair of 4X1 linear, I see you still have a good stock of "GTO Blue" spray paint.

R
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