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Ebay AL-811H, What Have I done?

338_MtRushmore said:
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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RF Parts has a matched quad of Taylor 572B's for #319.80 or the cheaper PRC tubes at $44.95 each if you are not worried about a matched set. Single Taylors are $79.85 or you could go with their limited NOS Cetrons at $199.95 EACH. LOL The matched Taylors are a bit more than twice the price of the 811A's but then again they have two and a half times the plate dissipation rating too.
 
The Taylor 572b is $80 and the 811a prc is $55. What is the advantage of the 572b over the prc? Plate dissipation on both are 160 watts.

I keep seeing to keep the key time under 5 seconds with a 15 second cool down when tuning. Would the 572b or PRC allow me 10 or 15 seconds of key? That could make sense to spend the extra money to tune much faster.
 
nomadradio said:
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
Click to expand...

I ran mine at 240 as I do my ICOM PW-1.Never any issues.Also I purchased the 811A tubes from Ameritron & they never had an issue.

SIX-SHOOTER
 
338_MtRushmore said:
The Taylor 572b is $80 and the 811a prc is $55. What is the advantage of the 572b over the prc? Plate dissipation on both are 160 watts.

I keep seeing to keep the key time under 5 seconds with a 15 second cool down when tuning. Would the 572b or PRC allow me 10 or 15 seconds of key? That could make sense to spend the extra money to tune much faster.
Click to expand...

The 572B has a 160 watt plate dissipation rating whereas the 811A has a plate dissipation of only 65 watts. The numbers I stated above ARE correct. Either you misread the ratings on the RF Parts site or they screwed up. Wait.............I just checked RF Parts. That PRC 811A for $55 is rated at 160 watts. They claim it has a "graphic" plate which I take to mean graphite plate. Note they are available only in limited quantities. IIRC there were some 572Bs that were made that would NOT handle full plate voltage that the 572B should due to closer element spacing. I believe they were relabeled as heavy duty 811As and are to only be used as a replacement for 811As due to the lower voltage ratings.
 
338_MtRushmore said:
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.
Click to expand...
Welcome to "How to blow your ham Radio Budget" 101.
 
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We will have to see what the amp looks like. Hopefully it just needs a good cleaning and minor repairs. I appreciate all of the input, and I'm sure I will have many more questions when this thing shows up.
 
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I had an AL-811 for several years. With reasonable care in tuning it up you shouldn't have any problems. You can almost buy 2 sets of 811A tubes for the cost of the 572B tubes.
Only problem I had with the amp was it needed more padding capacitance on 80 meters. Easy fix.
I have an AL-80B now. Much nicer amp and much quieter too.
 
811A's are fine for sensible SSB use but for balls to the wall 11m use or on AM they are a poor choice.Even W8JI the designer of most of the Ameritron amps admits the 811A's are being used beyond their design limits but for SSB voice service it is not a big issue. Take too long tuning up or running AM however is another issue.
 
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I just saw it didn't come with any tubes.
I wouldn't have paid that much for it but that is water under the bridge.
 

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