Eighty six dollars a troy ounce.

[W3RSW]

Just received a couple of brand new Eimac 3cx800a7's.  -gorgeous and almost hate to use them except as displaying them as works of art. Their outside finish looks like silver. They have a much finer external finish than my 1987 date coded ones.  I hope that attention to detail carries to the internals too.

So at 11.5 ounces each, about 10 Troy ounces, their value is $86/T.O.

With all the adequate safeguards of GM3SEK's triode control board or, say Alpha 89's boards, these will last me the rest of my lifetime...  barring a freak extended flashover, tube defect or similar.

They'd better, ... at three to four time the market price of .99 fine silver.

[Steve - K4HX]

So..... what are you going to do with them?  A big leenyar?

[W3RSW]

Stick them in a used alpha 89 or maybe use one in a conversion of my HB twin 8875 amp after some fan to blower mods.  I have already installed SEK's  triode control board in it along with pwr supply step start, glitch shut downs, etc.

I dunno, HB still puts out 1200 pep on very early 8875s.  Yeah, light linear usage or 100 watt AM all these years and watched grid drive like a hawk.  Always tuned up with 2 tone and a scope. My current plastic rig has 2 tone built in.

For serious am ( sure miss the ol' WFDNET times) I stick with the JJ (sort of) 813x2 by 2 rig.

[Steve - K4HX]

Nice selection you have there!

[W3GMS]

Rick,
If after thinking and thinking and you just can't think of any use for them, be aware that my Ten Tec Titan amplifier uses a pair!! 

Hope all is well.

Joe, GMS

[W3RSW]

Um hmmm; I'm hoping your Ten Tec is still meeting specs, even if not going much over.

Hey you two, actually they can be saved in a bank vault as heirlooms for the kids.
I can see it now.
" The ol' man must've been crazy. What are they? Off to the dump with these."

Stuff going as about the same over here Joe. No real improvement. I'm going up to Pirates game today with son in law.. Big break for mois and should be a fun day.

[W3GMS]

Enjoy the game Rick.

73,
Joe, GMS

[W3RSW]

Longest game I ever attended. 14 innings plus two and a half hour rain delay after the first inning and a half.  Pittsburgh finally won it 2 to 1 after stranding bases loaded runners twice.

 On the brighter side, the new ( to me) PNC stadium is pretty nice, open plan, not a bad seat in the house.  Great view of the rivers, city and river boat stern wheelers.  Good Beer too.

[W3GMS]

Yea Pittsburgh!    Even though I live closer to the Phillies! 

Sounds like even with the long session, you had a good time and that's what its all about.  Good on the 807's!

Joe, GMS 

[Steve - K4HX]

You picked a good year to go! The Pirates are on track for their first winning season since the early 1990s. Right now they have the best record in baseball.

The stadium is great. I was there a few years ago. The view from the North Side back towards downtown is quite appealing with he yellow bridges and the skyscrapers. The old Three Rivers Stadium was horrible for baseball- OK for football, but horrible for baseball.

Since you were already on the North Side, you should have swung by the Penn Brewery and had a Penn Pilsner or a Penn Gold and maybe some good German food.

www.pennbrew.com

Longest game I ever attended. 14 innings plus two and a half hour rain delay after the first inning and a half.  Pittsburgh finally won it 2 to 1 after stranding bases loaded runners twice.

 On the brighter side, the new ( to me) PNC stadium is pretty nice, open plan, not a bad seat in the house.  Great view of the rivers, city and river boat stern wheelers.  Good Beer too.

[W3RSW]

Yeah, we had seats in the nose-bleed section right field between home and first and view was spectacular.  Walked around the stadium on river side to the Riverview club, open to all, for dinner.   Maybe the Pirates will continue their streak..   it's been a long time.  Big slump last year.

My son lives in McDonald, just south of Pitt Airport, flies KC-135's from the Guard refueling wing so he's been to the Penn Brewery several times. Couldn't make it with us Sunday, so just son in law and me.  He's not sorry he missed the long, rained out game.

Anyway, next post will be why I'm so enamored with Eimac's focused anode tubes, probably the acme of tube technology in a twilight era.

[W3RSW]

Fun with Eimac focused anode tubes.

In the '70's Eimac came out with their original 8873/4/5 series along with big brother 8877, I think pretty much as a "thank you" to amateurs.  "73," and don't forget the series started with "88's."    The 3CX800A7 series and pulse rating counterparts came later.

The construction of these tubes is fascinating to me. I believe it is the height of triode tube technology.

The conduction (8873) and three air cooled designs (8874/5/7) allowed a lot of freedom in an amplifier design in air handling and power.  The tubes had finely controlled grid spacing so that the grid  aligned the passing electrons by field manipulation without intercepting too many of them, hence low grid current.  Interelectrode spacing was critical, very small between the cathode and grid, much larger between the grid and anode, hence high gain for a triode,  Mu around 200.  Exotic materials were used in construction including gold which at that time was, say, $135/oz. albeit in very small quantities plating the grid wires.

I'll also briefly mention that designers of some very high powered focused ray mil applications in the late 80's were very interested in the low grid intercept concepts for entirely different reasons and were not even aware that the design and application of such already existed.  Their problem was that the aluminum grid wires in the construct were evaporating with repeated pulses after a limited number of 'sessions'. Um, ok, they were brought up to date.

The 8873/4/5 series were designed so that a pair would comfortably handle a kilowatt average power input based on the old FCC standard of one KW input. Voice SSB service allowed easily 2kw pep input and 1200 watts output.

Eimac trusted the appliance manufacturers to know what they were doing and hoped that amateurs would also be knowledgeable or at least get proper instruction on amplifier usage and limits.

They were reasonably priced for the era, almost too much so because outfits like Dentron plugged them in with no grid current limiting /shutdowns, no cathode input tuning, and got by with this because of the Pi net. output of the driving transceivers and the relative cheapness of the tubes.  The 8875 with lateral cooling fins allowed a simple muffing fan to cool it.

There is a ton of literature on the net about the folly of this approach, modifications to the Dentron and similar amplifiers with axial cooled 8874's and 3cx800a7's in later decades.  Eimac engineers I suppose were never enamored with Dentron for their cheap amps and I guess many an 8875 met its demise in hammy hambone and worse chaps' hands.  Perhaps the sales people cheered in both camps. Regardless, expense and material costs increased, high roller industry and medical decamped for other technology and sales decreased.

So on the the 3cx800a7.   -This bottle came later and was touted to industrial and medical as well as hamdom.  Some of you more knowledgeable might have corrections or more to add.  The 8874 (only one of the original threesome), the 8877 and the newer 3CX800A7 were also touted for non-ham application.

A pair of 3xc800's is easily able to handle the 1500 watt pep FCC output limit imposed later.  Now for the real mystery to me and others.  The FCC's hand may be in this, possibly in 'suggestions' to Eimac, although other than apocryphal suppositions I can't find any real first hand documentation.

The March, 1983 original design spec's of the 3cx800a7 called for 2500 fully loaded plate voltage.  The later released December '83 followed by April '87 'watered' this down' to 2200.  All other related specs. followed in the revision including the useful power output, originally rated at 1370 watts per tube down to 750, "magically" now half of 1500.  That is very significant de-rating for whatever reason.

Due to the grid sensitivity of these tubes to overcurrent, current manufacturers are much more aware and have designed reliable and fast acting protection of the grid and other tube elements and have also taken advantage of the original March 1983 specs. although only hinting as such in advertising.  Modern transceivers can now limit their output driving an amplifier, some full power overshoot (over a set point, even over ALC) from a bad few notwithstanding.

I was enamored with the 8873/4/5 series so much that I built a homebrew amplifier using a pair of 8875's, finished in '82.  Bought them from Ceco Communications in July 1981.  They still have original output.  I had no grid overcurrent trip for most of their lives but respected a limit.  Resurrected the amp. after a dormancy of 20 plus years and installed GM3SEK's triode protection board with all the ancillary HV supply, etc. recommendations.  I'm a believer in these rugged (if properly used) tubes.

I'm getting 1300 watts pep, two tone, (LP100A wattmeter), 40 meters on my original pair of 8875's with 1600 volts, Ep loaded, 42 watts drive into input pi net, , 48 ma. grid, measured 5/16/2013.  Unbelievable little tubes, 32 years old.
 
So the 3cx800's are established, upgraded companions.  Thought I'd better get a new, certified pair while they're still made.

[Steve - K4HX]

I had an MLA2500 for a short while. It was capable of 1 kW easily and 1200 without going outside the specs. It seemed like a very nice compact design for a legal limit amp at the time. I sold it to a guy taking it on a DXpedition.

[W3RSW]

Yes it is a compact rig; many were made and still show up on EBay and festers.  You probably know all this stuff already. Too bad the 8875's were discontinued.  8874's are still made but very expensive.  The three holer alpha that used '74's is the easiest of all to convert to twin 3cx800's. just plug in the tubes and add another small filament transformer in series with the existing filament.  Most guys just  stuck it on the deck where the third hole got blanked.  A little artistic swirl with the plenums using turbo tubing and your done.

 Pdahl (Hammond maybe still does) had a complete set of upgrade and stock transformers for the Dentron and Alpha amps for the necessary HV, no sag, more kickapooh juice.

As we get older a revised weight limit shack might be in order along with a one story house 'n stuff related.  -a two part (deck & pwr. Xformer ) Alpha would be nice, fully capable of 375+ AM with plenty of headroom up to over 2.2k pep.  Kinda heading that way, but nothing else seems to be moving on. Shack keeps growing despite best intentions. I guess you Know the feeling. Probably took advantage of some of this with the Williamsburg move? No? 

[Steve - K4HX]

Three moves in five years. Yea, I got rid of a lot of stuff. I still have too much!

[W3RSW]

Here ya go. Just popped up. Full scrote, sort of.. More for your shack.

http://www.ebay.com/itm/Dentron-MLA-2500-Ham-Lienar-Amplifier-Amp-Eimac-8875-Power-C-MY-OTHER-HAM-GEAR/181155225643?_trksid=p2047675.m2109&_trkparms=aid%3D555003%26algo%3DPW.CAT%26ao%3D1%26asc%3D142%26meid%3D8813251567491974090%26pid%3D100010%26prg%3D1076%26rk%3D5%26sd%3D360514158965%26

[W3RSW]

Hokey gentlemen.  Here's more of the saga.

Have obtained a used Alpha 89 with tubes matching the amp. build date that still put out a decent legal limit though somewhat down.
I'll rotate the new 3cx800's in it , say every two years.  ..or not, the new ones are so gorgeous.

Of course, right after getting the new Eimacs, RF Concepts comes out with a whole line of those and others that I mentioned in another thread at half Eimac's price, even touting low grid intercept ones.  They seem to think they'll be quite reliable.
Remains to be seen.

Here is a link to a mod article that for my purposes shows much about the  89 amp. I am quite pleased with it although it seems to hang out on 7200 daytimes too much.
You know the type...
https://picasaweb.google.com/kfourso2/Alpha891162010

[AJ1G]

You picked a good year to go! The Pirates are on track for their first winning season since the early 1990s. Right now they have the best record in baseball.

[/quote]
Great to see the Pirates in the hunt this year, but the best record in baseball?  Maybe for teams from the state of Pennsylvania.  Last time I looked tonight, the Red Sox had the best overall record in MLB  at 87 and 58/.600, just a hair ahead of the Braves at 83 and 57/ .599.  The Pirates are 1.5 games behind the Cardinals in their division at 81 and 61/.570. Hope they make in through the  playoffs, a Pirates/Red Sox WorldSeries would be great. USAir would have to lay on some more Pittsburgh/Boston and Pittsburgh/Providence flights.

[W3RSW]

Yeah, the Pirates just dropped a whole series to Cards, in town of all places.
The big slide like last year may have begun.

[Steve - K4HX]

Nice amp Rick. You should have plenty of headroom on AM.   

Hokey gentlemen.  Here's more of the saga.

Have obtained a used Alpha 89 with tubes matching the amp. build date that still put out a decent legal limit though somewhat down.
I'll rotate the new 3cx800's in it , say every two years.  ..or not, the new ones are so gorgeous.

Of course, right after getting the new Eimacs, RF Concepts comes out with a whole line of those and others that I mentioned in another thread at half Eimac's price, even touting low grid intercept ones.  They seem to think they'll be quite reliable.
Remains to be seen.

Here is a link to a mod article that for my purposes shows much about the  89 amp. I am quite pleased with it although it seems to hang out on 7200 daytimes too much.
You know the type...
https://picasaweb.google.com/kfourso2/Alpha891162010

[W3RSW]

I hate to dig up a necro like this but a search for ' Troy Ounce' just saved me a ton of background writing.  Just wanted you all to know that new Eimac 3cx800a7's are now running $1500 each from what I've seen on another forum.   So yeah it looks more like Sotheby's in the cards around here every day.  

I've barely run the new Eimac pair I bought in '13 since the original '97 pair that came with the used Alpha built in '97 still truck along with only about 10 watts more drive required for 1500 output than the new ones.

I'll go down to the basement shack and call up a couple of Excel spreadsheets on the ASRock Atom 330 showing performance shortly after getting off this iPad.

I'll title it "3cx800a7 performance specs in an Alpha 89" for future faster reference for anyone interested.

[W3GMS]

I hate to dig up a necro like this but a search for ' Troy Ounce' just saved me a ton of background writing.  Just wanted you all to know that new Eimac 3cx800a7's are now running $1500 each from what I've seen on another forum.   So yeah it looks more like Sotheby's in the cards around here every day.  

I've barely run the new Eimac pair I bought in '13 since the original '97 pair that came with the used Alpha built in '97 still truck along with only about 10 watts more drive required for 1500 output than the new ones.

I'll go down to the basement shack and call up a couple of Excel spreadsheets on the ASRock Atom 330 showing performance shortly after getting off this iPad.

I'll title it "3cx800a7 performance specs in an Alpha 89" for future faster reference for anyone interested.

Hi Rick,
So far, my Eimac 3CX800's are doing well in the Titan 425.  If I ever need new ones, I think I will spring for the Taylors.  Heard good things about their 800's. 

https://www.rfparts.com/tubes/tubes-trans/tube-tran-taylor/tubes-taylortran-3cx.html?p=2

73,
Joe-GMS 

[W3RSW]

They sure look good Joe and if they last nearly as long, a good value. Wonder if ex-RKR or Dishtronics is still offering their line at about Taylor's price? 

Interested if your Titan runs about same gain and levels as the 89?

Well I may just be the caretaker for the next owner anyway if nobody wants to attend Sotheby's auction. 

[KD6VXI]

Taylor is Merritt Arnold,  RF Parts.

Why go to a middleman when you can get straight from the importer?

Or,  if you have a commercial I'll account  Greenstone is the place.   

--Shane
KD6VXI