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Author Topic: New 4-1000A modulated by 4-1000As AM Project - Fabio II Reborn  (Read 173327 times)
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ka4koe
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« Reply #25 on: April 11, 2013, 09:23:51 AM »

Where did you get your 4-1000s?

Philip
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« Reply #26 on: April 11, 2013, 11:42:29 AM »

Where did you get your 4-1000s?

Philip

Hi Philip,

Yes, 4X1's are rather scarce these days compared to yesteryear.   There was a time 20 years ago we could get them easily for $20 - $50 each at the flea markets. The BC and commercial rigs used them, but not anymore. So the supply has dried up.

I would put out "wanted" ads on the various QTH.com, etc boards and you will get replies. There are many older hams who have hoarded them thinking they wud build an amp someday, but never did.

The CB QRO and audiophile guys never embraced the tube, so there should be many out there.

Axe the seller to put a piece of white paper behind the tube and report if there are any "coffee stains" on the glass.  This is a good indication of hours on the tube. Also axe about plate deformaties or glass heat dimples.

 Be sure to use the black, plasdick socket for RF use. And a chimney is important to get air up and around the plate cap.

They are a great tube and will take a lot of abuse - as long as air is run by all the seals.  A chimney and good air flow will see to that.

T


** Update:  The 4X1 RF deck is almost all wired and I will post some pics soon.  I'm awaiting a robust vacuum relay for the antenna switching.     Next, the modulator deck.
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« Reply #27 on: April 11, 2013, 01:30:48 PM »


 Be sure to use the black, plasdick socket for RF use. And a chimney is important to get air up and around the plate cap.
T
[/quote]

Hi Tom,
I have some of the Eimac cast sockets designed for forced air cooling.  I forget the Eimac part number but they are very heavy duty and have the opening for a hose connection to handle the cooling.  Have you found any problem when using them?
Joe, GMS
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K1JJ
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« Reply #28 on: April 11, 2013, 02:05:10 PM »

Hi Joe,

I have used them both for RF service up to 10M with no problems.  If we look at the alum ones, the lead length is not much different than the plastic sockets.

But I have been warned by some to stay wid the plastic sockets for RF and leave the aluminum ones for audio modulators.

Another thing is cooling.  I like the more direct path for air and ability to drill additional holes around the socket when using the plastic version.  Though, I have drilled holes in the alum sockets for more air too.

T



 
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« Reply #29 on: April 11, 2013, 02:24:06 PM »

Thanks Tom.  Yep, I think I have a pair of the cast ones and it would be no problem putting those in modulator service.  So when I look for the RF side, I can go with the less expensive ones. 

My scheme is to use one high panel similar to yours but to put a steel Bud shelf above the tubes with ample spacing so air can escape and then use ceramic HV FT insulators to bring the single common line from the plate caps / parasitic suppressors to the upper deck.  The upper deck will allow mounting of all the tank capacitors.  The HV RF choke will be on the same lower chassis as the tubes are on centered between the two tubes. The grid circuit will be beneath the tubes on the lower chassis. 
We shall see how it all works out. The CG-309 will serve as the plate iron.     

Thanks again for the comments on the sockets.

Joe, GMS   
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« Reply #30 on: April 11, 2013, 03:00:10 PM »

In some cases, I'm singing to the choir here:

The Eimac SK-500 aluminum socket was designed for forced air from a centrifugal pressure blower, not a less forceful fan or inadequate blower.  With adequate pressure, plenty of air is circulated around the tube base seals and up the chimney annulus. 

Q= AV ;  air quantity equals area times velocity across an orfice.

With adequately designed blowers, with piping at least equal in diameter to the socket cooling intake, pressure is constant from the blower outlet right up to the first real restriction, regardless of the piping and angles encountered, less some small turbulence drop.

Notice that in the SK-500 their is no socket mounting flange in the airstream.  The pins engage cylindrical sleeves inside the cavity.  So the 5 each, 1/2 in. holes and the center 7/8 in. hole in the tube base itself is the first real restriction.  They are designed to allow air flow from the center of the tube ( the vacuum seal tit) and around each of the five pins.   And yes, by all means the proper chimney or equivalent lantern glass of the right annular diameter is required.  In the Eimac chimney the top is rounded thus deflecting the air flow around the plate cap seal.

You can find a bronze SK-500 instead of the aluminum. It can be pretty nice.
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« Reply #31 on: April 11, 2013, 04:40:18 PM »

In some cases, I'm singing to the choir here:

But your voice is welcomed OM!  Hope you and your wife are doing well.  Missed the one on one eye ball QSO this year which happened last year at the Slab Bacon's.

Thanks for your perspective on the 4/1 tube sockets.  I have some nice squire cage blowers that work well under back pressure conditions.

73,
Joe, GMS 
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« Reply #32 on: April 11, 2013, 05:06:15 PM »

OK on the sockets, Rick.

You mentioned turbulance.   Over the years I have run tests and tried a lot of air techniques. It seems that turbulance can have a big effect on efficient air flow.  The eddys and cross currents can really stifle our flow sometimes.

I remember opting to use smooth fiberglass 4" hose one time cuz the ribbed plasdick hose caused less flow due to turbulance.

I've seen the effect of using a non-symmetrical tube layout that caused some tubes to hog all the air due to pressure pockets and turbulance.

That's why I like to use a small sub-chassis with a direct path for air flow, with no bends or restrictions except for the actual tube openings.  

Another problem with obstructions is noise. I once ran a 3CX-3000A7 that had a loud high-pitched whistle.  I never found the reason for it after a lot of effort. Seemed to be coming from the tube fins. The only solution was to run it at a certain air speed to reduce it to tolerable.

With my new 4X1's in the RF deck, I tried the blower last night and hear a soft air rubble. There is something going on in there, perhaps related to the wiring and components underneath. A direct air connection wud be bettter, I know.    Air noise on ssb is usually tolerable, but on AM low frequency rubble or high freq noise will pass thru. On ssb it may be filtered out.

T
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« Reply #33 on: April 11, 2013, 06:45:40 PM »

My question is to Tom or others who don't like the sound of blowers etc? Did anyone here ever consider using water cooled tubes? There are equivalents of the 3CX3000A7 out there plus smaller versions used in the chip manufacturing industry.

I don't know if the distilled water that you can get a grocery stores for use in irons or for batteries is pure enough? I also have read about using pure antifreeze. Seems to me a small volume water pump would work. As a matter of fact I have seen such systems on eBay for cooling laser systems that have all the hardware including the radiator etc. You could go GREEN when such a system is attached to your home hot water system Grin Grin Grin
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« Reply #34 on: April 11, 2013, 07:31:21 PM »

no reason to deal with blower noise these days. I have this hooked to the hot tub.  Grin



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« Reply #35 on: April 11, 2013, 07:35:08 PM »

Hi Terry,

I did recently look into water cooling for the new AM rig, attempting to run silent and deep.  One of the guys here does it for a living and told me what I needed to know in addition to having some used tubes and sockets. After learning the full practical real-whirl requirements, I decided the infrastructure was more effort and expense than it was worth.  In contrast, air cooling is just a matter of a blower and your're done.  The water cooling is not as easy as it sounds, I'm afraid.

I decided to run the blowers at a slower speed using a Variac and monitor the temp closely. Also, I have a lot of plate dissipation available which will permit the tubes to run cooler.  The real solution wud be to move the rig at least 10' away. Some day I may do that.

T
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« Reply #36 on: April 11, 2013, 07:41:02 PM »

Pretty slick, B!  That looks like it is set up for 80M from the taps on the tank coil.   But if the impedance is low enuff, judging from the double plate chokes and double vac variable caps, it might be 160M.  There's a lot of BIG guns on CW down there.  IMD would not matter on CW.

From what I learned, the reason for the extra run of tubing around the inside of the amp is cuz there is a certain voltage per foot of insulation.  If it were 1 KV per foot, you'd need 4' of hose for a 4KV amp, etc. before it could be touched outside safely.

There are other ways to do it like using PVC pipe to enclose the water hose and run it directly out.  


Another consideration is how clean are the water-cooled tubes?  I was told many are designed for heater use at 13.9 Mhz, but still others are used in big mofo audio amps.  I never see published IMD specs on these watercooled tubes.

In contrast, the linear air cooled tubes are quite well documnted for IMD.

T
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« Reply #37 on: April 11, 2013, 09:46:32 PM »

Who was the buzzard AM guy that ran water cooled tubes with a closed cooliung system that used glycol circulated thru car radiators with electric fans on the outside of the building???   It is a memory from my childhood
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« Reply #38 on: April 12, 2013, 09:41:55 AM »

Cool water amp  pix. I like it.  Noticed the extra run of tubing.  I guess the voltage gradient is on the inside through the water stream. Yeah, pure water is an insulator. ...but add just a pinch of salt and your in for a super scrubbing in the ol' hot tub.  I always liked looking at the glass tube illustrations of yore in the Eimac literature.  Hey, why not go boiler?  Grin
Look at the advantages. Takes a lot of heat to go from liquid to steam.  You could have bubbles while you bathe.  " Mom, check out my lobster red tan!"

Thanks for thoughts joe. We are doing reasonably well. No change though. Yeah, miss you guys over there.  Sounds like your having fun whomping up a 4x1 design.

Tom, yes your using the pipe organ pressure box design.  The box is at constant pressure, a reservoir box so to speak (sing   Grin ) and all the little pipers don't affect it much unless you blast a 12note chord.  Interesting remarks on your singing tube.  I think your right; the vanes were resonant at a certain air flow rate.  Laminar flow is always preferred to turbulent in a system if you want oversize diameter, easily modeled results.  But again, if you want max. Flow, messy and loud, you use a constant pressure system, where flow quantity is dependent more on the pressure than the friction of the delivery system.
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« Reply #39 on: April 12, 2013, 09:17:14 PM »

I keep talking to myself to get this thing built into an operational amp and not a college display. It still needs a filament blower but at least it is almost instant on.

What do you use for a water system and how much HV can that hose and distilled water handle?

Carl


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« Reply #40 on: April 13, 2013, 07:02:43 AM »

WOW,

There is some great stuff going on here!!

Nice layout on the RF deck T. It looks very RF efficient in layout and design.

On the waves - - - G




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« Reply #41 on: April 13, 2013, 09:09:37 AM »

Way cool. Where do you get stuff like that?  Yeah, big flanger with w/c and blower ( for bottom seals I suppose). Tap water pressure and moderate flow rate ought to be plenty.  Distilled water, and changed out to prevent copper ions from running around, heh, heh.

Well, for starters get the TMC GPT-10 k  RF amp. Tank coil assay. Complete with band switch good for 15kw , 2 to 30 mhz , currently being offered on eBay.  A couple of vacuum variables and your on your way.   Don't think 1.8 MHz would be much of a stretch.
I'd attache the link for the coil, but this d..n iPad is too awkward.
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« Reply #42 on: April 13, 2013, 12:43:28 PM »

Pic #1:  First light!

Pic #2 - check this out - I welded up a rock-solid, permanent lazy-Susan pedestal for the RF deck to make it easy to work on.  It can turn 310 degrees and give EZ access to all parts.

I still have dress up work to do on the RF deck, but it is wired and all the component modules have been tested. All the supplies, keying, filaments, neutralization, pi-network, etc are working FB.

Need some nice knobs for the front panel - maybe on eBay or at Deerfield...   Still need to build cabinets for both units.

I really do like the pedestal effect and find myself pushing it to different positions for some reason.... Grin

Now onto the modulator deck.  After careful thought, I've decided to stay with the 4-1000A modulators, tetrode connected.  I will run the screen voltage regulated between 500 and 1000V to give the option of running class AB1  or AB2.   AB2 will generate more audio power when needed, though with grid current - not as clean as AB1.  With 10 dB of NFB and the solid state audio driver, it shud be a clean lash-up.

T


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There's nothing like an old dog.
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« Reply #43 on: April 13, 2013, 12:46:19 PM »

As the whirl turns:


Check out the new vacuum antenna relay in pic #2.  I got tired of blowing out receivers due to relay air gap arcing.  This one cost me $329 but is the best out there. Notice the effort to keep the mechanical strain off of the terminals. Still need to finish wiring it. Luckily it was the only part I needed to buy for this whole project. Good junk box here.

I ground-strapped all the RF components together, C1, C2, etc., so there will be little currnets through the front panel, etc.

The relay towards the back with the copper straps is a 160M .002 uf cap padder that gets switched in for C2 when needed.  

Towards the rear-bottom are the grid and screen supplies. They both use Variacs.  The RF deck grids use a regulated -95 fixed voltage and -120 volts of grid leak bias.  Total about -210 volts for class C operation.  The regulated fixed bias prevents RF rectification "creep" due to charging of the  bias supply from the RF grid drive.


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« Reply #44 on: April 13, 2013, 12:48:21 PM »

Thanks for the comments, Big G!

I wish it looked as good as your old 4X1  X 833As.

Say hi to "TC" and the rest of the Salt City Rockers for me...  Wink


------------
Pic #1:  Notice the short leads from the bandswitch to the coil.  Copper strap rules.

Pic #2: The monolith from "2001 - A Space Odyssey "


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Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
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« Reply #45 on: April 13, 2013, 12:50:53 PM »

And, of course, Yaz had to get into the act. " Could you get away from that darn workbench and take me for walk?"

I hope to have the full rig working and on the air before Deerfield, about 3 weeks away.  Lots to do yet, especially proofing and testing  - and IMD and THD optimization.

T


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There's nothing like an old dog.
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« Reply #46 on: April 13, 2013, 04:14:35 PM »

T

Rig looks good.


Something I'm not getting,  a week or two ago we were looking at painted empty panels.  Now an almost completed rig is pictured.

You build a rig, it takes maybe a month,  I build a rig and it takes a decade.

I have to speed up my work.

Fred
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« Reply #47 on: April 13, 2013, 04:27:18 PM »

T,

Whare ya gonna put the chicken??


klc
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« Reply #48 on: April 13, 2013, 05:34:11 PM »

Hey Freddy, get this...   He's not even retired like you. Roll Eyes

He still works (yeah, a few hours, possibly daily), takes Yaz on a daily
stroll  through the woods and still produces big rigs, from scratch, in
a few weeks!  Cheesy

Maybe you need to acquire a nice Springer Spaniel... Grin

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« Reply #49 on: April 13, 2013, 06:32:47 PM »


You build a rig, it takes maybe a month,  I build a rig and it takes a decade.

Fred


And, it's not over yet. The real pain is about to begin.

The JJ Rule of Symmetry states:  "It usually takes as much time to troubleshoot, test, modify, optimize and perfect a homebrew rig as it took to build it in the first place."

It took us 200 hours to build?  Expect to spend another 200 hours testing, modifying and optimizing.

This is a proven scientific fact that may be nominated for the Nobel Prize in Quackery any day now.   Wink


T
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There's nothing like an old dog.
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