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[VK3BL]

Must be some really strong stuff to smoke down under to make this  statement.

Its not really that controversial if you understand the tank circuit is tuned to provide maximum efficiency at maximum output.  As you decrease output from your tune point, you lose efficiency.

As efficiency decreases, plate dissipation increases.

There is nothing worse for set of 811As than tuning up at full power, then decreasing drive (say to 400 watts output) and then running a continuous mode. 

But hey, keep the Ad Hominen attacks coming.  Why bother engaging with my argument when you can insinuate I smoke something that is illegal in my country, but increasingly legal in yours... if anyone is hi hi, statistically its more likely to be one of you guys.  Shouldn't blame you guys though... you've got a president who fancies himself as a king, and built his career on trashing the character of other people...

[W8JX]

Its not really that controversial if you understand the tank circuit is tuned to provide maximum efficiency at maximum output.  As you decrease output from your tune point, you lose efficiency.

You have a problem with math I see. I do agree efficiency increases when drive is applied but plate dissipation rapidly increases as you reach higher output levels too. Example, at say 500 watts out if you are lucky to get 65% efficiency (as it will likely be lower) that mean at least 750 watts in and 250 divided by 3 equals about 85 watts and well pasted 811 ratings (but well withing a 572's ratings). You spin the cylinder in "gun" hoping that plates do not melt as you modulate.

[G3RZP]

The unknown is how well the tubes match in terms of plate current at a given grid voltage. There is a lot to be said for the complication of a separate bias pot for each tube. The downside is an increase in production cost.

[K8AXW]

Boys (and girls, not to be considered sexist) whenever a crowd gets into a pissing contest, which has been going on here for some time, SOMEONE is going to get wet!

This whole thing could have been terminated a long time ago if the operator simply swapped out the tubes which would narrow down the problem immediately.

THEN the problem could be eliminated pretty quick......or THEN we could get into  the pissing contest which could be more productive because the reasons for the problem would be narrowed down considerably! 

[VE3LYX]

You mean to tell me a tube swap has not yet been tried ?
Klazy!
donVe3LYX

[KA9UCN]

Well said AXW!
    As a ham who has played with the American made  811, with no horizontal extra anode fins-811A with the added horizontal cooling fins, the Russian 811 with the extra metal stamped to the side and the Russian “572" that was a great heavy plate 811 but not the tube a graphite 572 is.  On a test bench. I have pushed soft tubes to destruction. Just to see when they melted or flashed. I have never owned a Chines 811. The 811 I have played with will work with the plates bright red up to the point of burning holes or severally distorting the plate. When the plate distorts visibly the idle current will most certainly change. Sometimes higher sometimes lower. The tube will still work after cool down but the properties have changed and should be replaced. At a lower voltage the 811s in GG, I have used do not have any plate color ideling but when transmitting. Usually 1 or more tubes showed some color before the others. I just run them that way.

   Just my opinion. The best thing the Ameritron 811 amp could have dun, would be to reduce the plate voltage to 1500VDC+/- and settle for 150 watt a tube max. in SSB. It is a very over stressed amplifier that sometimes gets a bad name by being ran to hard and or abused. If taken care of and ran correctly. The tube should last until the emissions drop. I have never owned an Ameritron amplifier so I can not comment on anything other than the way they run the tubes.

   Joe KA9UCN

[W1QJ]

I think there should be a special forum for "peanut whistle" amps.  Leave this forum open for full power amps, OK, 1200 watts and above.  1200 watts and less goes to the peanut whistle forum.  Too much bandwidth being spent on amps that can't get out of their own way.

[G3RZP]

Might I suggest that before pontificating too far, you all read the RCA Ham Tips for October 1939 (Vol2 nr 5) where they describe how they maltreated an 812 (not an 812A) until holes were melted in the plate and it subsequently provided full output?

http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips0205.pdf

Now I am more than ready to accept that the results from an original RCA tube and those from a Chinese or Russian tube bearing the same number may very well have an extremely tenuous relationship. My experience - amateur and professional - has been that for the same part number, US manufactured tubes always have the edge.....(Tin hat, head down, dodge the bullets!)

[VK3BL]

This whole thing could have been terminated a long time ago if the operator simply swapped out the tubes which would narrow down the problem immediately.

The issue is some people believe there is a problem, whilst others (myself for one) believe this behaviour is normal for the AL-811.

I believe the operator could tear their hair out trying to find a set of tubes that are fully balanced, and that doing so would be a waste of economy, as the less balanced trio would work just fine and provide adequate life in ICAS.

[VE3LYX]

I think there should be a special forum for "peanut whistle" amps.  Leave this forum open for full power amps, OK, 1200 watts and above.  1200 watts and less goes to the peanut whistle forum.  Too much bandwidth being spent on amps that can't get out of their own way.

Isn't that special!
donVe3LYX

[W8JX]

I think there should be a special forum for "peanut whistle" amps.  Leave this forum open for full power amps, OK, 1200 watts and above.  1200 watts and less goes to the peanut whistle forum.  Too much bandwidth being spent on amps that can't get out of their own way.

I do not think it is the rated power output as a benchmark as much as how well it is designed for its rated power. Example, a SB200 is a far more rugged amp than a AL811. Maybe a forum for light duty amps like AL811 series using 811 tubes or amps using sweep tubes and one for amps with 572's or better by design not swapped in.   

[W1QJ]

I think there should be a special forum for "peanut whistle" amps.  Leave this forum open for full power amps, OK, 1200 watts and above.  1200 watts and less goes to the peanut whistle forum.  Too much bandwidth being spent on amps that can't get out of their own way.

I do not think it is the rated power output as a benchmark as much as how well it is designed for its rated power. Example, a SB200 is a far more rugged amp than a AL811. Maybe a forum for light duty amps like AL811 series using 811 tubes or amps using sweep tubes and one for amps with 572's or better by design not swapped in.   

Well I think if we could turn back the hands of time and we could now purchase  RCA 811A tubes, would would not be discussing the Al-811 and Al-811H amps.  Stick those tubes in those amps and all the problems we see will go away and they will probably do rated power.

[W8JX]

Well I think if we could turn back the hands of time and we could now purchase  RCA 811A tubes, would would not be discussing the Al-811 and Al-811H amps.  Stick those tubes in those amps and all the problems we see will go away and they will probably do rated power.

Well if you want to go back in time even a old RCA 811 cannot hold a match a new old Cetron 572.

[KM1H]

But hey, keep the Ad Hominen attacks coming.

I hate that phrase as it is mostly spouted by the technically devoid such as the Nichrome King and the like as a way to stop a thread before they are too deep in the excrement to climb out.

Speaking of attacks you best stop the one on President Trump before things get out of hand. He has only been in office for 22 days and the Socialist Loonies havent stopped their attacks since long before the election.

I do not think it is the rated power output as a benchmark as much as how well it is designed for its rated power. Example, a SB200 is a far more rugged amp than a AL811. Maybe a forum for light duty amps like AL811 series using 811 tubes or amps using sweep tubes and one for amps with 572's or better by design not swapped in.

Those amps make cheap drivers at reduced power for tubes with handles and can often be found with all bad tubes at less than a SB-200 that needs some TLC to start with. Plus the AL's cover 160, have a better input network, have a power & VSWR meter that actually works fairly well and all you need is 2-3 572B's

AND 3CW20000A7's are a bargain.

Carl

[W8JX]

Those amps make cheap drivers at reduced power for tubes with handles and can often be found with all bad tubes at less than a SB-200 that needs some TLC to start with. Plus the AL's cover 160, have a better input network, have a power & VSWR meter that actually works fairly well and all you need is 2-3 572B's

Lack of 160m is not a deal killer and its input is "better" because it is easy to tune???  And as far as built in SWR meter in amp that is not a big deal either as I watch power and SWR externally when tuning and if you have reasonable resonant antennas you do not even have to watch SWR much. To suggest a AL811 is a more rugged amp than a SB200 would be foolish. If they had been built as cheaply as AL811 amps are they would have all gone to junk pile long ago and would not still be a viable amp today.