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Author Topic: 811A Tube Availability - time to panic?  (Read 1629 times)
K7GRR
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Posts: 50




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« on: October 27, 2007, 08:28:20 PM »

I have an AL-811H, and have been looking at getting an AL-572.  In looking at the costs of re-tubing either of these, I was a bit alarmed to hear that at least one (more) factory has quit making 811's as they have little profit from them.

Looking further, RFParts.com has been out of Taylor 811's for several months and the expected restock date has slipped (again) to next month...

Now, they have no Taylor 811's, but the Marshal 811's are $197.60 for a matched quad.  Taylor 572's are $179.80 for a matched quad.

Egads.
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W5RKL
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Posts: 897




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« Reply #1 on: October 27, 2007, 08:52:56 PM »

Retubing an AL-811H with Ameritron 811's is $109. I would go with Ameritron, especially since the AL-811H is their amplifier.

The 811 is a very popular tube and I seriously doubt they will become obsolete anytime in the near future!
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K7GRR
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« Reply #2 on: October 27, 2007, 09:07:33 PM »

I don't *need* to retube, but I thought it was interesting that the price difference between 811's and 572's is shrinking.
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ON4MHO
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Posts: 28




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« Reply #3 on: October 28, 2007, 06:16:11 AM »

Hi from Belgium. Don't be too afraid about theses tubes. They're quite easy to find. I bought mine on Ebay United Kingdom. This is a set of 4 Russian (Svetlana) I paid about 100 dollars. You can find good deal on this site from sellers in the former Soviet Union, as well a new production Chinese tubes. However, I prefer the Russian tubes which are bullet proof. Hope this helps. 73's de ON4MHO, Arnold.
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HA6SST
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Posts: 110




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« Reply #4 on: October 29, 2007, 08:40:48 AM »

Do not panic. Plenty of 811 tubes are available from both Svetlana in the former USSR and various Chinese manufacturers.

HA6SST
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KE4DRN
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Posts: 3734




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« Reply #5 on: October 29, 2007, 03:39:24 PM »

hi,

the china tubes have caused more problems by
damaging radios as reported on the yahoo ts520 forum.

try to avoid the china tubes unless you have no choice.

73 james
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KE3WD
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Posts: 5689




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« Reply #6 on: October 31, 2007, 10:27:19 PM »

Must be too much lead in their tubes, too...
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SSB
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Posts: 1




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« Reply #7 on: November 01, 2007, 09:33:19 AM »

If I were in the market for an amp using 811 or 872 tubes I would look at ANY amp using a 3-500z instead.  A 3-500z tube amp is a much better deal.

Alex....
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WA4DOU
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Posts: 436




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« Reply #8 on: November 07, 2007, 12:20:16 PM »

Put four (4) Chinese 572B's in it for $145 or four (4) Svetlana 572B's for $220 and be done with it or wait for Taylor 811A's to become available again. The very fact that they expect to have the tubes available in early to mid Nov. 2007 suggests that they're going to go on being stock items. At $72 for four (4), it's practical to have them for backups.
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W6IEZKEN
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Posts: 29




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« Reply #9 on: November 07, 2007, 01:05:07 PM »

    I came up with another approach.I switched to a single 833C to replace the four 811A's/572B.The 833C is $109 and is the best dollar per watt tube I could find.A big advantage is a single tube has less parts and sockets to malfunction.The tube is large physically and looks like a cow's utter but it puts out 1300 watts and doesn't require a matched quad at $200.You will have do do some re-engineering but after that you will save a lot of money and increase reliabilty.RF Parts and Penta labs both have them.Their are some differences between the 833A,C,D.The 833 filaments will look good when lit up under your Christmas tree.
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WB2WIK
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« Reply #10 on: November 07, 2007, 06:44:52 PM »

>RE: 811A Tube Availability - time to panic?  Reply  
by W6IEZKEN on November 7, 2007  Mail this to a friend!  
I came up with another approach.I switched to a single 833C to replace the four 811A's/572B.The 833C is $109 and is the best dollar per watt tube I could find.A big advantage is a single tube has less parts and sockets to malfunction.The tube is large physically and looks like a cow's utter but it puts out 1300 watts and doesn't require a matched quad at $200.<

::Where'd you get the 10V at 10A for the filament?  There's no room in the AL-811/H for another filament transformer...  Also, the 833C runs 1300W PEP okay, but at 4000V anode voltage.  The AL-811/H only provides about 1700Vdc, not nearly enough to run an 833C at full power.  Can you provide some photos of your conversion so we can see what you did?

WB2WIK/6
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W6IEZKEN
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Posts: 29




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« Reply #11 on: November 08, 2007, 06:51:25 PM »

     One of the hams e-mailed me and I accidentally deleted it,if you would E-mail me again I'll answer your question.My amp is not an Ameritron but is homemade from surplus components and has always had an external power supply which makes modifications easier.The whole focus was on using cheaper available tubes and reducing the number of parts.I failed to mention that it is a switched bias amp and operates class C for CW and AM at 85% efficiency which does require 3-4KV on the plate.It operates class AB1 for SSB.The limitation on most amps is the power supply not the tubes.The plate transformer on the Ameritron 811A amp is only rated at 450 watts continous.If you run digital modes at 90% duty cycle and 30% amp duty cycle you can see the problem.If you use plate transformers that will put out the rated power input continously you won't have the power sags and overheating when you send digital mode MARS traffic overseas continously for eight hours.You can find Mil.Rated transformers on Ebay,flea markets,surplus if you are patient.My filament Xfmr for the 833C was ten bucks on Ebay.Believe or not in the old days hams wound their own filament,chokes and plate transformers.Peter Dahl will sell you one Hypersill plate transformer for the 833C at $458.
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W6IEZKEN
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Posts: 29




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« Reply #12 on: November 08, 2007, 07:40:35 PM »

   Some additional info on the 833 tube.The 833A is rated at 350 watts plate dissipation and go's to 600 watts on the 833D.If you remove the four 811'A's or four 572B's you should have enough room for an 833 by raising the top cover 2-4 inches.You can only get full power ratings by going to an external power supply.The filament voltage is different but the power is the same and if you use a Mil. filament Xfmr it will handle the 11 amps of the 833D easily.If you stick with the original power supply it's not worth it.If you want full power that you can put a brick on the key and come back a month later and it has the same power out use the 833,it beats a $1200 4CX1500B.An 833 amp project was in the ARRL Handbook in the 1960's.The 833 has more distortion than the 4CX1500B but so do the 572B and 811A's as well as all the 800 series tubes.The plate dissipation is not the only factor in determing power output even at the same class of operation.Look at the 4-1000A and 813
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