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Author Topic: Swan 1200-X mod to use 30KD6  (Read 2000 times)
K7FJ
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« on: February 15, 2006, 10:11:56 AM »

I am modifying my old 1200-X to use the 30-volt filament version of the 6KD6.  My plan has been to wire the filaments in series and connect to the 120 vac power through suitable RF inductors.  An old thread from 2002 warned about cathode-fil insulation breakdown but it seems to me that a tube designed for series string filaments should have adaquate insulation for such service.  I have suitable filament transformers to power the filaments in parallel at 30 volts but that would add a lot of mechanical work.   Comments?
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WB2WIK
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« Reply #1 on: February 15, 2006, 10:21:57 AM »

One of the reasons to use a transformer, besides safety, is the xfmr will limit inrush current.  When you connect directly to the AC mains, your inrush current limit is pretty high.

Of course, the old 5-tube "AC-DC" table radios of the 50s and early 60s had heaters in series but usually also a resistor in series with them, too (since the heater sum was less than 120v).  Other than causing some nasty shocks to users, they seemed to work...

WB2WIK/6
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