[AMRadio] Filament Voltage

[Donald Chester]

>From: "Dan Hall" <kj7fx at tdn.com>

>I have very poor filament voltage regulation on the Gates BC1-J.

First, verify the filament voltage using an external meter.  RF may be 
affecting your reading.

If the primary voltage is indeed varying that much, I suspect you have a 
problem with the electrical wiring in your house.  I assume you are running 
it on 220 volts.  The kind of load you are talking about shouldn't affect 
voltage anywhere near that much.  Check your house wiring, or have an 
electician do it if you are not completely confident in your ability to do 
it yourself.  Left unattended, problems like that have been known to result 
in house fires.  Do your room lights flicker when you transmit?

If you are running it off 110 volts, poor line voltage regulation may be a 
problem.  My transmitter runs off 110, and I had the same problem (although 
even on 110v my filament voltage didn't sag that much).  I rewired it so 
that the low power stuff including the filaments runs off one side of 
neutral, and the HV power supplies run off the opposite side.  Now, when I 
kick on the high voltage, the filament voltage kicks UP slightly.  With this 
arrangement, with both circuits sharing the same neutral wire, the voltage 
drop from the HV primary current adds to the output voltage on the opposite 
leg. The final tubes like that little boost in filament voltage and grid 
drive when they are called on to deliver power.

Don K4KYV

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