I bought a 3-500 amp that another ham tried for some time to get to work.
I fired it up and was quite disappointed in the output (very low). The
problem was that
about a volt was lost across the filament choke and wiring. I added a
small filament transformer in the primary as a "BOOST" transformer. This
brought the filament voltage up to
spec and it worked very well after that.
Another problem is that if there is much drop in the AC power
wiring. The filament voltage will drop when you key down.
73
Bill wa4lav
At 03:07 PM 12/10/00 -0800, you wrote:
>Perhaps your filament voltage is a bit low. low voltage = low emission.
>Maybe the transformers can't give the 4x(15A/tube) required by the 4 tubes?
>.....Merit W6NQ
>>
>>
>>I have started work on a new amplifier (80 - 10 meters) utilising the
>>popular grounded grid design but with a slight difference than the norm
>>as I use four valves in parallel, of the AMPEREX 4-250 type. I still
>>would like to break the 1 KW barrier on output.
>>
>>I have a similar working one I build in 1999 but although it is working
>>it is not very efficient and prone to destroying chokes and by-pass
>>capacitors. Power output is also way below what I expected .. and not
>>breaking the 1KW barrier.
>>
>>I run the valves with +/- 3,400 Volts on the plate and the filaments have
>>two transformers connected in parallel giving the 5 Volts at +/- 15 Amps.
>>
>>I
William L. Fuqua III , P.E. EE
Department of Physics and Astronomy
CP 177 Chemistry Physics Building
University of KY
Lexington, KY 40506-0055
Phone 859 257-4155
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