The 811A tube in its native condition. Blown to Hades.

[nomadradio]

I was gonna list this 811A tube on fleabay, mostly for grins, not so much for profit. Yet another listing that starts with "It's dead, Jim".

Just a bit better than cluttering the local landfill. Until it rolled off the bench and onto the floor with a resounding "POP!", tinkle.

One bright spot, it makes the carnage a lot more visible with that pesky reflective glass out of the way.

I have come to see this as the natural state of the 811A tube. It's rare to find a user who treats it gently enough to survive service in a ham linear.

The oppposite side of the anode isn't quite as clobbered, but still has a hole in it.

But if you hold the light just right you can see the grid wires through the blow hole.

Probably not suitable for fleabay now. But definitely easier to photograph.

73

 

[BayouRadioAmplifier]

yep, seen this before. I have an AL-811H.

but a friend sent me some old used Russian
811's, and they are holding up.

 

[nomadradio]

Treat 'em like they're the last set of tires you'll ever own. Easy on the throttle, easy on the brakes.

73

 

[Shockwave]

They have not made an accurate equivalent of the original RCA 811A tube, in over 30 years. The 811A tube became completely worthless as soon as the six radiator fins were removed from the anode and replaced with a flat fold on each side. That is not the way the original tube was constructed and that is why the new tube fails regularly. Avoid 811A tubes in any application that has a carrier and replace them with 572B tubes.

 

[AudioShockwav]

They have not made an accurate equivalent of the original RCA 811A tube, in over 30 years. The 811A tube became completely worthless as soon as the six radiator fins were removed from the anode and replaced with a flat fold on each side. That is not the way the original tube was constructed and that is why the new tube fails regularly. Avoid 811A tubes in any application that has a carrier and replace them with 572B tubes.

I put 572's in mine and never replaced another tube after that.

73
Jeff

 

[Shockwave]

I put 572's in mine and never replaced another tube after that.

73
Jeff

I consider the 811A as an obsolete tube out of production many years ago. It's replacement is the 572B.

 

[nomadradio]

I like 1-800 Toll Free's characterization of the 811A. "All the linearity of a half-wave rectifier".

73

 

[Amperex]

811A have the thinnest plates of any transmit tube. I would use one above 150 watts output SSB and 100 watts peak AM.

 

[Shockwave]

I like 1-800 Toll Free's characterization of the 811A. "All the linearity of a half-wave rectifier".

73

So, is it a 6X4 or 35Z5?

 

[Captain Kilowatt]

I like 1-800 Toll Free's characterization of the 811A. "All the linearity of a half-wave rectifier".

73

Sure, when you drive the piss out of them. Run properly, they are not that bad at all. Basically they are a 6L6 on steroids and 6L6's are run in some commercial broadcast gear in both RF and audio service and run quite linear, actually.

 

[Shockwave]

Sure, when you drive the piss out of them. Run properly, they are not that bad at all. Basically they are a 6L6 on steroids and 6L6's are run in some commercial broadcast gear in both RF and audio service and run quite linear, actually.

Imagine an 11 meter rig running a 6L6 audio tube, modulating a 6L6 RF tube? 50 years later, the Tram D201 is still hard to beat.

 

[nomadradio]

6L6 on steroids

Hmmm. 811A, high-mu triode.

6L6, a beam power tetrode, or as the brits call it a Kinkless Tetrode.

Not a similarity that just jumps out at me.

73

 

[Captain Kilowatt]

Hmmm. 811A, high-mu triode.

6L6, a beam power tetrode, or as the brits call it a Kinkless Tetrode.

Not a similarity that just jumps out at me.

73

You are right. I had a brain fart. The 807 is basically a 6L6 on steroids. Both are electrically similar. Older broadcast transmitters used 807 in both the RF driver stage as well as in the audio stages from preamp up to modulator drivers. No idea why I said 811A. Must have posted that before my morning coffee.

 

[nomadradio]

No idea why I said 811A

Welcome to old age.

73