Broke a 811a tube.

[SMILEX2692002]

Since I never use my 811H amp I finally decided to take the tubes out and put them back in there boxes and put the amp in its box and store them all.
Tube 1 out, tube 2 out, tube 3 out, tube 4 . Crack, the top broke off. Luckily I didn't cut my hand ha.

Are the Rf parts tubes worth buying?
I see they only want like $22.00 for a replacement 811a tube.

Anyway after I get a replacement tube I will want to make sure it works so I guess for now I will just leave it the amp on my desk.

My tubes were the originals from Ameritron and I hardly ever used them. So now I will have an odd duckling in the mix. The tube from RF parts is probably a better quality one anyway.

 

[hookedon6]

...Anyway after I get a replacement tube I will want to make sure it works so I guess for now I will just leave it the amp on my desk. .

RF Parts 811a tubes are as good as anyones elses chinese tubes,

ASK about their refund policy before you purchase, I seem to reember they a quite good at refunds

BTW: you can operate that amp with only 3 tubes, just leave the "hole" nearest the fan empty

 

[MudDuck442]

That is correct. You can run it with only 3 at reduced power in and out. Or if the tubes are pretty much new order up one and throw it in. They won't be exactly matched but they will work just fine. Back in the day when the 811-A tube was very popular they didn't match the tubes they just made sure they weren't completely different and put them to use. In other designs I would be the first to start to jump up and down about it but in this amp you have options...run the 3 tubes until you are ready for a set, then replace all 4, or get just one now and run them for a few days to get impurities out then off in the closet it goes.

 

[Captain Kilowatt]

Having matched tubes in a grounded grid design amp is not really necessary. If you do run with just three tubes be aware that the position of the TUNE and LOAD controls will be somewhat off from normal due to the higher impedance of the output circuit.

 

[SMILEX2692002]

Just waiting for the new tube to arrive. RF parts seems to have very fast shipping.
Do I have to do anything special when I get the new tube once I install it?
I have tried to find more info online. Some say its best to let the amp stay on stand bye overnight before using it.
Others say it is only required to leave the amp on stand bye long enough to see if the tube has any issues. If no issues then its good to go.

 

[Captain Kilowatt]

A lot of people talk about "burning in a tube". It is BS. I spent 22 years in the broadcast business and we never "burned in" a tube. Some of the high power ceramic tubes were monitored after 24-48 hours and the filament voltage readjusted but they are a little different than a simple glass 811A. Let it heat up, check for color, put the power to it and watch for arcs, or bluish or purple color that indicates a gassy tube and if all looks good go for it. Run it according to specs and have fun.

 

[SMILEX2692002]

A lot of people talk about "burning in a tube". It is BS. I spent 22 years in the broadcast business and we never "burned in" a tube. Some of the high power ceramic tubes were monitored after 24-48 hours and the filament voltage readjusted but they are a little different than a simple glass 811A. Let it heat up, check for color, put the power to it and watch for arcs, or bluish or purple color that indicates a gassy tube and if all looks good go for it. Run it according to specs and have fun.

Ordered the tube on Sunday got it today. Very fast shipping with Priority mail from RF parts.
Put the tube in and powered on. I saw no issues. Waited a few mins and put the power to it. Works great.
With this new tube installed I'm seeing a increase in power from what I had before with a 40 watt drive.
With a 50 watt drive I'm seeing about full output on 10 meters SSB.

It might not be the best designed amplifier on the market. I'm happy with mine.

 

[hookedon6]

...It might not be the best designed amplifier on the market. I'm happy with mine.

the person that designed the 811 & 811h was given a price range and was told the design an amp to fit it.

you are correct, there are a LOT of them in use

 

[Captain Kilowatt]

the person that designed the 811 & 811h was given a price range and was told the design an amp to fit it.

you are correct, there are a LOT of them in use

You mean Tom (Charles) Rauch W8JI?

 

[hookedon6]

You mean Tom (Charles) Rauch W8JI?

yes,.. a cut & paste from anoeter site
Tom is replying to a comment about the 811h being higher priced than the 811for profit reasons only.... BOLD is mine

"Tom Rauch:
Quote from: WX7G on February 06, 2010, 07:24:10 PM

Ah, by my analysis it is not the design engineer's specs, it is the marketing folks specs that rate the AL-811 for 500 W CW.

As I stated, there is no compelling technical reason I can see to not rate the AL-811 for 600 W CW. But to rate it so would 'cannibalize' sales of the AL-811H; a portion of AL-811H sales would be displaced to AL-811 sales.

The AL-811 looks to be a loss leader. The higher price of the AL-811H very much offsets the the addition of one socket, on 811A, and one plate cap. More profit.


No. It is not just one tube and socket difference!

The 811 was built to be the cheapest possible way to build an amplifier. The 811H has circuit upgrades necessary when four tubes are used. Three or less tubes are stable under all tune and load conditions on ten or fifteen meters. Add one more tube and the amplifier requires neutralization for "any load" stability.

If you look at the Collins 30L1, you will see it is notoriously unstable. It has undergone a series of stability mods from Collins, and they even recommend adding a certain length cable from the exciter to the amp. This is because Collins never neutralized the 30L1. It can be made to self-oscillate just by meshing the load control fully and peaking the plate with no driver attached! The Dentron Clipperton does the same, and it is also not neutralized.

If you look at the Heath Warrior, Gonset GSB-1000, and other 4x 811 amps you will see they are neutralized.

The Ameritron AL811H is neutralized, as is the AL572 amp with four 572B tubes.

So it is not true that the 811H is priced higher for more profit. The 811H has a neutralizing circuit and other components necessary to make it stable and work better with four tubes, this included shielding changes and other mods, and those components result in higher cost.

While both are "built to be cheap" amplifiers, personally I'd pick the 811H because it is a small price difference for the better circuitry

 

[KG0MN]

I would have sent you a like new tube for the cost of shipping. I picked up an Ameritron AL-811 for about half the cost of a new. I pulled all the 811s out and put new 572B tubes in it and it is now very happy.