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Ebay AL-811H, What Have I done?


I assume that you know it will require a connection from the send jack to tx.

Also, unless you know what you are doing,.. Keep your hands out of the innards.;)
 
but this is my first foray into sucky bulb amps. I don't even know what question to ask other than what do you think?
https://www.ebay.com/itm/Ameritron-811H-Ham-Radio-HF-Amplifier/292872852201?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
I think you are mistaken about "Sucky Bulb Amps." Real radio equipment glows in the dark! Ameritron is Quality Ham Radio equipment and if you take care of it, it will outlast your radios. Don't run a splatter box into it or over drive it.
 
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I would replace the tubes with the larger 572B.

It is a drop-in replacement for the 811A and much more reliable. Won't deliver any more power than the original types in this amplifier.

The 811A is pretty fragile in this kind of amplifier, easily damaged by mistuning, excessive drive power or high SWR.

The 572B will provide a safety margin that the 811A can't.

Good chance that it was sold without tubes because the original set failed.

The 572B is more expensive to buy, but cheaper to use. They'll last longer.

Have a close look at the band-selector switch. It seems to be a weak point in this amplifier. Any sign of darkened switch contacts or scorch marks is a red flag for caution.

73
 
I think you are mistaken about "Sucky Bulb Amps." Real radio equipment glows in the dark! Ameritron is Quality Ham Radio equipment and if you take care of it, it will outlast your radios. Don't run a splatter box into it or over drive it.
My apologies. In the future I will try to refrain from calling a vacuum tube a sucky bulb.

I would replace the tubes with the larger 572B.

It is a drop-in replacement for the 811A and much more reliable. Won't deliver any more power than the original types in this amplifier.

The 811A is pretty fragile in this kind of amplifier, easily damaged by mistuning, excessive drive power or high SWR.

The 572B will provide a safety margin that the 811A can't.

Good chance that it was sold without tubes because the original set failed.

The 572B is more expensive to buy, but cheaper to use. They'll last longer.

Have a close look at the band-selector switch. It seems to be a weak point in this amplifier. Any sign of darkened switch contacts or scorch marks is a red flag for caution.

73
I was under the impression that the 811a would do fine provided you weren't a complete idiot while tuning and didn't drive the snot out of them. If you all say the 572b is worth the 2.5 times the 811a, I guess I'll have to go that route. I assume with the 572b there is no reason to baby them output wise?
 
Well I owned an Ameritron 811H for many years & it performed very well.I replaced the 811A tubes with 572B tubes & saw no advantage & they lasted half as long as a set of 811A tubes.They ran a bit cooler but for the difference in cost I much preferred the Chinese 811A tubes.I only sold the amp because my wife purchased me an ICOM PW-1 Solid State Amplifier as a Retirement gift.The friend who purchased the 811H still has it & loves it.The 572B swap was highly overrated & overpriced in my honest opinion.Put about 65 watts of drive into the 811A tubes & it will serve you well but put more than that into it & the tubes will not last & the output difference is not worth the stress you put on the tubes for a few extra watts.I know many believe that 100 watts more will make a huge difference & the only difference it will make is in how long the tubes last & the feel good from the wattmeter reading.It's NOT a Kilowatt amplifier so just let it do what it is suppose to do & have fun.If you blow a tube you may run it with just three tubes & it works just like the 811 (3 tube) model until you can get a new tube.Of course remove the bad tube & keep on talking.Best wishes with the new toy & 73.

SIX-SHOOTER
 
Cool! Nothing like first-hand experience.

Does leave me with one nagging suspicion, though.

Were you running it from a 120-Volt circuit? This type tube does not like voltage drop on the filament. Causes the temperature of the filament to run too low. Fouls up the chemistry of the tungsten alloy and causes the tube to become prematurely weak.

As a rule, directly-heated filament tubes last longer on a 240-Volt circuit.

Might explain your experience.

Might not.

Just a thought.

73
 
Mt' R: I have had the 3 hole version for like 15 years now (1994 production code). I have found it to be a solid performer.
The present day 811a's are not the tube of old. The old RCA/Sylvania's and GE's were much better tubes, however the present day
Taylor Premiums/Machlett/Penta's are not bad (all made in same factory) Quality control is much better since Penta took over watching the production. I would stay away from the "Generic" no-name versions, the failure rate is about 25%.
The Svetlana's were the best, but no longer in production, The Russian G-811's are about the same. Those brands were made for Military and much better QC.
The present day 811A's don't have the same Plate/Grid/Filament material or strength as the older versions. However treated properly will last a good long time. I try to keep drive power in the 50w PEP range and the amp will yield a good solid 500w out with Grid current well with-in specs. The 4 whole version maybe 10 watts more will yield a solid 600+ watts, yes Ameritron say's 800w but is that little difference worth pounding the tubes...NO
Now as to 572B swap, this tube is much stouter construction wise than the 811A. The so-called extra output comes from the fact, most drive them harder due to better construction. The output difference, no one will notice on the receive end.
They are a better tube however in my HO, worth twice the price: that will be your budget debate.
I have had a set of Svetlana 572B's in mine for at least 6-7 years, have literally beat them to a pulp. Several Field Day operations, couple contests etc... They were around 600+ watts when installed, after all this time still 450-500w+ all bands.
I have a NIB set of Svetlana and another set of OLD/USA made NATIONAL tubes (4 each) 811A's here in-stock when ever the need arises to swap them out.
I will most likely keep my eyes peeled for a set of Machlett's or Taylor premiums 572B's at Hamfest's or the Swap sites that are priced right and purchase those for additional stock. I have no plans to get rid of the AL-811 amp anytime in the near future.
I like NOMADE suggest operation at 240v, the power supply does exhibit better voltage regulation at that voltage than 120 volts.
I have however run the Field Day operations at 120v and they operate fine, they just exhibit greater voltage swings when loaded down.
I do have this one observation, Ameritron uses the SAME power supply in the 3 tube and 4 version, this is not to say the 4 tubes version lacks in power supply. Just interesting they produce both amps with same supply, and just leave one tube out.
There you have my 2 cents worth of info, both are good solid amps when run conservatively and will last many years service.
All the Best
Gary

PS: If you plan ANY AM Operation the 572B is your only real choice (at least the Taylor 811H/D version) and output in the 50% of rated PEP SSB operation, otherwise you will KILL them quickly!
 
My apologies. In the future I will try to refrain from calling a vacuum tube a sucky bulb.
To be honest with you I have WATTS envy! If I hadn't blown my radio budget for the next 20 years I would buy a brand new one. I have amps all over the place and have never used one on the air.

To sum it up I would say you did very well for yourself.
 
I have to agree with BJ on his post above regarding the 572B replacement. If your 572Bs were only lasting half as long as the 811As something was DRASTICALLY wrong somewhere. The plates on the 811As are tissue paper thin and the tubes have a dissipation of only 65 watts each whereas the 572B has a plate dissipation of 160 watts......MUCH higher rating. While the plate may glow orange in an 811A it will not show colour in a 572B and if an arc should occur the 811A will blow a hole thru the plate whereas the 572B is likely to just shrug it off. Swapping out 811As for 572Bs is never done for more power output among those operators that know better.....the gain figures for each are the same. Higher output can only come from raising the plate voltage. 811As are comfortable at 1500-1800 volts max whereas 572Bs can take 2400-2700 max. If I ever had an amp with 811As in it I would not hesitate to swap them out to 572Bs.
 
...edit.... The plates on the 811As are tissue paper thin and the tubes have a dissipation of only 65 watts each whereas the 572B has a plate dissipation of 160 watts......MUCH higher rating...the gain figures for each are the same....

This is the correct info on the 811- 572 swap. Dissipation ratings tell the truth.

You won't get any more output power with the 572's because the amps power supply is the limiting factor, but,... you will have more tube "headroom" for tuning errors.

I ran Svetlana's in my 811h (4 tube) and had zero issues.
 
The only part I don't understand is why no one actually complains about the 811a not lasting. Surely there must be some 811a's still in use, or has everyone upgraded?

For just a few hundred more I could have 572b's, but for just a few hundred more I could have 3-500z's, for just a few hundred more I could have... see where this is going?

I'm still not sure what I'm going to do, but I'm not too fond of spending $350 for a set of 572b's.
 

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