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 Post subject: Heater To Cathode Voltage
PostPosted: Oct Wed 25, 2006 10:59 pm 
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Joined: Oct Fri 06, 2006 6:07 pm
Posts: 221
Out of curiousity I would love to know when heater to cathode voltage becomes a serious design consideration-only when creating cathode-follwers and split-load inverters? Is it only an issue when grounding the center tap of the filament winding to common negative?


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PostPosted: Oct Wed 25, 2006 11:11 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: San Jose, CA USA
One of the most important cases, of course, is rectifiers, where you can end up with hundreds of volts between heater and cathode.

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Tom K6VL


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PostPosted: Oct Thu 26, 2006 1:36 am 
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Location: Pocasset, Cape Cod, MA
>>Is it only an issue when grounding the center tap of the filament winding to common negative?

Yes, and if the tube in question has its own heater winding, you can return the center tap to the midpoint of a voltage divider.

Part of the problem is the voltage rating of the cathode insulation, but part is thermionic emission from the heater to the cathode (the cathode acts as a plate since it is positive with respect to the heater). This can inject hum into the cathode circuit.


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