Ameritron 811 only putting out 200 watts

[Araraces]

Have a 811 amp that I sold to an individual that was working great when sent.
During shipping the nut holding the plate choke came loose. After he put the nut
back on and installed tubes amp is only putting out 200 watts. Tubes were sent separate and were full output when shipped. Any idea as to the cause of the low power output?

 

[sp5it]

Not at all.

 

[Shadetree Mechanic]

Might be something wrong with the nut holding the microphone?

Welcome! Sorry I couldn't resist.

Does he know how to tune it?
Is it wired for 220 but plugged into 120?
Is he driving it with a QRP radio?

We really need more information if we are going to be any help. Maybe he can take some pictures of the inside that you could post here? Someone might be able to spot something.

Chris
73&51

 

[Araraces]

Might be something wrong with the nut holding the microphone?

Welcome! Sorry I couldn't resist.

Does he know how to tune it?
Is it wired for 220 but plugged into 120?
Is he driving it with a QRP radio?

We really need more information if we are going to be any help. Maybe he can take some pictures of the inside that you could post here? Someone might be able to spot something.

Chris
73&51

He has indicated to me running 120 and driving with 40 watts it was wired for 120. Also stated getting 200m plate
current and 20m grid current. Thank you for any help.
Ara
K4KKR

 

[Shadetree Mechanic]

He has indicated to me running 120 and driving with 40 watts it was wired for 120. Also stated getting 200m plate
current and 20m grid current. Thank you for any help.
Ara
K4KKR

Forty watts drive sounds low, how much power were you driving it with? I think it takes 100w drive for rated output?

 

[Araraces]

Forty watts drive sounds low, how much power were you driving it with? I think it takes 100w drive for rated output?

45 watts drive I was getting avg 420 watts out. 50 watts would get 500 out.

 

[wavrider]

I like your meter.

W8JI has some good info on his site about the 811 amps.
Several short comings with it.
So many variables. Input VSWR??
Is this happening on all bands or just one band?
Did any of the parasitic suppressors get broken or damaged? not getting B+ to tubes.
Need narrow it down to either voltage related??
Input related?
Output tank issues,( band switch)
I have rebuilt several of the input circuits on this type of ameritron amp.
dont take much drive to cook the input matching components.

 

[Amperex]

65 watts should produce 600 watts PEP out. Sounds like some tubes were damaged during shipping. i assume 1800 volts no load.

 

[nomadradio]

it was wired for 120.

There's yer problem.

If it was powered from a wall outlet with serious voltage drop this causes the temperature of the thoriated-tungsten filament to fall while keyed up. Pulling power from that kind of filament with a reduced temperature will make the tube prematurely weak.

There are two tests that can confirm this.

First, put this set of tubes into an amplifier that was delivering a normal power level. If this set of tubes "breaks" that amplifier, you have your culprit, or culprits.

Second, put a new set of tubes in this amplifier and see what improvement if any you see.

You won't find any other kind of tester for that tube. There was one lab-grade Hickok tester used by Western Electric back in the day that would test a 811A, but they don't go cheap. Pretty sure their number was "KS15874".

73