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Author Topic: AL-811 Tube Recommendations  (Read 5238 times)
NT4I
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Posts: 17




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« on: November 16, 2012, 04:58:57 PM »

I am looking to re-tube an Ameritron AL-811, and was looking for a recommendation on tubes.
I did discover that Surplus Sales of Nebraska has new 811-A JAN (Cetron) US made for $35 each.
I suspect that these tubes have some age on them and may not be the best for this amp?
Or should I replace the 811-A's with 572B's and be done with it? If so, what is the recommendation on suitable 572B's?

Thanks!
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W8JX
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« Reply #1 on: November 16, 2012, 06:52:22 PM »

I would try the JAN 811's as age is not really a factor for NOS tubes.
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K4RVN
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Posts: 778




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« Reply #2 on: November 16, 2012, 07:20:10 PM »

I would suggest the Taylor select from RF parts They claim each is testd and also give a 1 year guarantee for the 811A tubes.
The cost is around 68 bucks for a set of three matched . You really don't need them matched and could buy the tubes for around 21
plus change each. The main thing is they are tested and guaranteed. I have read that the Cetrons old stock have sometimes experienced the caps coming loose due to deteriozation of the fastening material. Don't know if that is true or not as I have not personally used any. I prefer a tested tube with a guarantee for less money. I have had good experience with RF parts. I have an 811 Ameritron and have not decided to go with the 572s as the 811As have done quite well so far at 550 watts most of the time.
I will decide later when I need to buy replacements, so have not decided not to use 572s.

Frank
« Last Edit: November 16, 2012, 07:23:39 PM by K4RVN » Logged
K0ZN
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Posts: 1553




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« Reply #3 on: November 16, 2012, 07:29:01 PM »

 Do some semi-serious research/reading around before you buy tubes.  There are some good posts here on eHam in the archives of
this section and in the product review section.  WELL worth your time and effort.

Based on all I have seen and read on here, Surplus Sales of Nebraska has a pretty "checkered" reputation and those tubes have not
been any better than new Chinese tubes....  best bet seems to be RF Parts....apparently, they actually check the tubes.
Cold reality is that none of the new tubes are near the quality of the old American made tubes from "back in the day".  I had that
driven home with my AL-811.  I had TWO of the original tubes go gaseous....vacuum failure. I ended up going through 6 new tubes
to find three that were good and have lasted fairly well. A couple of the replacement tubes went gaseous and one quickly developed
a hole in the plate structure. For the record, I do NOT abuse or "push" my amp....to the contrary. I grew up in the tube type world and
fully understand the care and feeding of them..... I just have seen a 50% failure rate on new 811A's !  Hopefully, you will have a much
better experience. I have purchased tubes and electronic components from RF Parts and they were easy to deal with. My experiences
with RF Parts was quite positive.

Re:572B's in an AL-811....there are a ton of comments on that subject too on here in the archives.  Kinda sounds to me like the 572B's are
little (literally, a LITTLE...)  better quality than the 811A's now available, but more expensive. I suppose they would be harder to damage by
improper tuning, etc., due to  the higher plate dissipation ratings. I guess technically, the plate voltage of the AL-811 is really way below
what is  optimum for 572B's....how big a deal that is, I can't tell you.... a lot of people do seem to do that swap....and some claim it is not
a good move.  Just understand, you won't get much, if any, more power
out of the box with those tubes. Again.... this would be worth digging into before plunking down your money as there seems to be alot
of myth and a fair amount of mis-information about this tube swap floating around out there.

No matter what source you get, I would strongly recommend you do a no-load burn in on new 811A tubes. You will probably have some other
"experts" jump in here and tell you it is not worth the effort, but I can assure you that based on what I have seen personally and
also read of the new production 811A's, as a minimum, it won't hurt and *may* help remove any residual gases. I know that the tubes that
I let "cook" over night for 12 hrs. or so have been more reliable. Obviously, if there is a mechanical construction problem with the tube internals,
it won't do anything to help with that. Admittedly, with 572B's there is likely less benefit. I also cycled my new tubes off and on multiple times
in an attempt to weed out any "infant mortality" related to the filaments. I built a small test fixture to do all this....much easier than
opening up the amp and then closing up with all the screws, etc.  Like I said.... these new tubes ain't what they use to be, so don't
be stunned if you find an early problem with a tube....

Lastly, check W8JI's website on this subject:  w8ji.com

73,  K0ZN
« Last Edit: November 16, 2012, 07:49:33 PM by K0ZN » Logged
NT4I
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Posts: 17




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« Reply #4 on: November 17, 2012, 07:47:54 AM »

Thanks for all the great information from everyone. Very informative from all who responded.
I'll report back after we decide what way to go.
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WX7G
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Posts: 6128




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« Reply #5 on: November 17, 2012, 09:50:41 AM »

I would buy a matched set of four 811A tubes from RF parts. You will then have one spare matched tube.
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N4CR
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Posts: 1672




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« Reply #6 on: November 17, 2012, 08:49:28 PM »

I got many years out of the Surplus Sales in my Collins 30L-1. When the got down to 500 watts, I bought some Chinese 572B's. Went through two sets. Right now they Surplus Sales tubes are in there putting out a solid 500 watts.

I sourced a set of NOS RCA 811a tubes from a local supplier. Haven't put them in yet, but I will this week while I'm on vacation.

For my money, the Surplus Sales tubes have been fine. They were $25 ea when I got them.

The problem with 572B's in an 811 amp is that the plates never get hot enough to getter. That can lead to a gassy tube long before the same tube would have gone gassy in a 572B amplifier.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
K0ZN
Member

Posts: 1553




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« Reply #7 on: November 17, 2012, 11:32:55 PM »


 N4CR....

Wow!  Where did you find NOS  RCA  811A's ?!  I would jump on some.  Everything I have heard is that they are virtually impossible to find anymore.

If you don't mind sharing, I would love to know a source. 

Thanks,   Jon,  K0ZN
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K4RVN
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Posts: 778




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« Reply #8 on: November 18, 2012, 09:31:12 PM »

Jon, This outfit in Florida lists 811As made in the US. I have bought a number of old stock tubes from them for my old radio and
also a 3-500 made in china. All were satisfactory. I think the 811as made in the US would have to be new old stock so here is a link
for you if interested. http://www.esrcvacuumtubes.com/vacuumtubes_tubelist.html
They were at the Atlanta hamfest a couple of years back and are good folks from my experience.
Also RF Parts Co has them listed.

http://www.rfparts.com/tubetran.html

Frank
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N4CR
Member

Posts: 1672




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« Reply #9 on: November 21, 2012, 01:34:53 PM »


 N4CR....

Wow!  Where did you find NOS  RCA  811A's ?!  I would jump on some.  Everything I have heard is that they are virtually impossible to find anymore.

If you don't mind sharing, I would love to know a source. 

Thanks,   Jon,  K0ZN

ESRC in Orlando. Link in above message is good.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
K2FOX
Member

Posts: 110




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« Reply #10 on: November 22, 2012, 08:23:40 PM »

Hi everyone and Happy Thanksgiving (late evening). I've purchased a wide variety of tubes from Penta Labs over the last several years http://www.pentalabs.com/about.html and found the tubes reasonably priced and durable. Three Chinese made 811's @ $18 each plus shipping last December. You would have to call for the current price.

Just another option...all the recommendations have been good.

-Jay

 
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N6AJR
Member

Posts: 9910




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« Reply #11 on: November 22, 2012, 09:45:32 PM »

Ameritron sells tubes for that amp, as they made it the first time.  and they are reasonable.  Don't waste the money or effort on 572's, the 8 11s are made for that beast.
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K0ZN
Member

Posts: 1553




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« Reply #12 on: November 23, 2012, 09:21:37 PM »


Thanks for the guidance/help on possible tube sources.  Much appreciated!

73,  Jon,  K0ZN
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KC4MOP
Member

Posts: 743




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« Reply #13 on: November 24, 2012, 03:29:18 AM »

I also purchased Taylor 811's for an Ameritron 811A amp and it really perked up back to full power.
Seems to be a tube that is easily abused and not a long liver. The amp I had was used, and I re-sold it to another buyer after installing a fresh set of tubes, to be fair to the new owner.
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N4CR
Member

Posts: 1672




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« Reply #14 on: November 26, 2012, 06:41:27 PM »


 N4CR....

Wow!  Where did you find NOS  RCA  811A's ?!  I would jump on some.  Everything I have heard is that they are virtually impossible to find anymore.

If you don't mind sharing, I would love to know a source. 

Thanks,   Jon,  K0ZN

ESRC in Orlando. Link in above message is good.

I went by there today and picked up two more NOS RCA 811A tubes.

I asked him if he had more and he said; "Sure, I have quite a few. 11 in the inventory and more that I have never inventoried but I know they are there."

So if you're at all interested in some vintage 811A tubes, this would be your opportunity to get some. He also has quite a few 811 tubes, so if you care about the difference, be sure to inform him. (811's don't have the dissipation enhancers on the outside of the plate)

There is a picture of an 811A here: http://www.dogstar.dantimax.dk/tubestuf/pinups/pinups.htm

Here's a picture of an 811: http://www.radiomuseum.org/tubes/tube_811.html

He said he had NOS RCA and Sylvania at least. Possibly Westinghouse as well. He's not into electronics, old tubes are his only business. He's a parts man not an electronics hobbyist, so please don't go technical on him.

http://www.esrcvacuumtubes.com
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
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