> A friend has a Ameritron 811A amp. Claims it puts out ~700+ watts
> into a DL.
If that is an accurate external meter, 700+ W is significantly in
excess of the rated output. Ameritron rates the AL-811 for 600W.
> I looked at the schematics, and aside from the extra tube and the
> plate blocking cap being doubled up, I really do not see any other
> changes.
There are significant changes in the input matching circuits.
Compare the two manuals.
> Both amps were being driven at ~65 watts from an Icom 756Pro3
Has your friend checked the VSWR between the amplifiers and the
Pro3? He may be seeing 65W forward but if the SWR is high, most
of that may be going right back to the Pro3 and never reaching
the cathode of the tubes.
According to the "typical" specifications in the respective manuals
the AL-811 gain is 9 dB (600W PEP output, 75W drive); the AL-811H
gain is 11 dB (800W PEP output, 65W drive). Since the amplifiers
have identical power supplies, 800W PEP output from the AL-811H is
a bit questionable with a 1000W (1500V/700mA) power supply.
73,
... Joe, W4TV
On 5/22/2010 11:41 AM, Mike & Becca Krzystyniak wrote:
>
> A friend has a Ameritron 811A amp. Claims it puts out ~700+ watts
> into a DL. Recently he bought a pristine Ameritron 811H amp. But
> surprisingly it only puts out ~600 watts. He drops in 4 new tubes
> and it still only puts out ~600 watts. Both amps were being driven
> at ~65 watts from an Icom 756Pro3
>
> I looked at the schematics, and aside from the extra tube and the
> plate blocking cap being doubled up, I really do not see any other
> changes. I sorta expected the tank "L" values to be changed slightly
> but that is hard to tell from the on line documentation.
>
> Anyone seen this problem before? Aside from recycling the amp is
> there any hope?
>
> Thanks
>
> 73's Mike K9MK
>
>
>
>
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