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Ameritron 811 help

Mudfoot

Mudfoot

Elmer
Jun 17, 2009
10,936
6,333
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Southeast Ohio
Can't seem to get full output following the instructions in the manual. Researching online, I read many different ways to tune. I have no problems with initial tuning, where I tune at low enough drive to reach 100 mA grid current and peaking out load and plate.

My problems start when I increase drive to reach 150 mA grid. I quickly exceed 450 mA of plate current. When I stay under 450, I only see around 400 watts.

Should I start tuning at a higher power? Are there better, more efficient and quicker ways to tune for full output quicker than what the manual suggests? I'd be interested in reading other 811 owners method of tuning up. I wonder if a pulser would be safer for me to use? I'm getting aggravated and likely gonna smoke this thing.

Figure I need me an amp Elmer.
 

Just peak the thing for max smoke and slightly advance the load so the grid current drops a bit. It's best to start low and work your way up. If the grid current is excessive then you have too much drive or soft toobs. Low output, high input swr and high grid current = soft toobs.

Ameritron amps are also less efficient on 10,11 and 12 meters. You will not see as much output there. Try 20 meters and see if things are better.
 
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Mudfoot said:
Can't seem to get full output following the instructions in the manual. Researching online, I read many different ways to tune. I have no problems with initial tuning, where I tune at low enough drive to reach 100 mA grid current and peaking out load and plate.

My problems start when I increase drive to reach 150 mA grid. I quickly exceed 450 mA of plate current. When I stay under 450, I only see around 400 watts.

Should I start tuning at a higher power? Are there better, more efficient and quicker ways to tune for full output quicker than what the manual suggests? I'd be interested in reading other 811 owners method of tuning up. I wonder if a pulser would be safer for me to use? I'm getting aggravated and likely gonna smoke this thing.

Figure I need me an amp Elmer.[/QUOTE

Take it easy Mudfoot, what band, how much drive and in what mode(s)?
Check the input swr between the radio & amp, if it is high the radio will fold back to
protect the finals
Also I would recommend using a keyer between rig & amp. Those little relays surface
mounted that they use to key the amp are borderline even though they are rated to
handle it.
Don't key down for more than 5 seconds when tuning up the plates in 811 tubes are not that stout, rest it in between plate and tune.
If you want to PM me to go over anything do it.
Click to expand...
 
Take it easy Mudfoot, what band, how much drive and in what mode(s)?
Check the input swr between the radio & amp, if it is high the radio will fold back to
protect the finals
Also I would recommend using a keyer between rig & amp. Those little relays surface
mounted that they use to key the amp are borderline even though they are rated to
handle it.
Don't key down for more than 5 seconds when tuning up the plates in 811 tubes are not that stout, rest it in between plate and tune.
If you want to PM me to go over anything do it.

Don't know why this was in with your quote so I reposted it in case you missed it
 
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Plate current and grid current specs are only guidelines for tubes. In the case of an 811 tube, they do not have a fragile grid or plate. What ruins these tubes is heat over time. Sure you need to be quick in tuning because an out of tune tank circuit creates high circulating currents which stresses everything. The safe way to initially load an amp is to start low and work up. Once you reach maximum normal output yu should make notations of the drive level, load and tune positions so you can return quickly to those settings. Then you can make the preliminary adjustments and in a matter of 2 seconds can tweak it and you are done.
 
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If your 811 is the three tube model then 400w is normal. I had the "H" version with four tubes. No one your working can tell the difference in your signal at 400w compared to 500w. Your tubes will last for years if you don't drive them to the limit.
 
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in ICAS the 811a (RCA) tube could be run at 65 watts plate dissipation, A three (3) tube amplifier could run 366 watts output and a four (4) tube amplifier could run 488 watts output, assuming 65% plate efficiency

The Chinese 811's have about 55 to 60 watts max.

375 watts CW is about max for an 811 amp, about 275 for RTTY
 
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I hate reading manuals. I just glanced over it and read where it said not to exceed 450 milliamps plate or 100 milliamps grid, during initial tuning. When I got to the final step, I kept it under those values, instead of increasing output power to max, max plate or max grid. Very easy to tune now. I think I was gun shy and had visions of it poofing. As I said, been 40 years or more since I had a tube amp.
 
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