Absolutely not! Doing so would ground out the positive of your HV supply assuming the HV center tap is also grounded. You could, in theory, use the split 6.3 volt winding (with resistors) as a dual filament source if the insulation is sufficient and can supply the amperage for the tube's demand. Then use the center tap as the positive supply point. But it is an ersatz way of doing it. And remember, 866's need time to preheat.Can I ground the center tap and use each half of the secondary with dropping resistors for a heater on (2) 866A tubes for a full wave power supply?
Can I ground the center tap and use each half of the secondary with dropping resistors for a heater on (2) 866A tubes for a full wave power supply?
The only way you could do something like this would be to ground the center tap and elevate the HV center tap to make a negative DC power supply. That would probably cause VHK issues elsewhere in the circuit.
Best to just get the proper filament xfmr, or ditch them in favour of SS diodes. That way, no extra holes needed, no filament power either.
The filament transformer is a separate 6.3vct unit. How would grounding the CT affect the high voltage supply?
It will put a dead short across the HV since the 866 doesn't have a separate, insulated cathode. The filaments will be at the positive rail voltage unless you make it a negative supply.
OK, got it. How about using a resistor in the primary of the separate filament transformer(6.3vct@10A) and connecting the 2-866a tubes in series with 5v ? The B+ would be taken from the CT of the filament transformer.
I find the data to 866A tube with a parallel configuration, 2.5V / 5A x2 for the heater. I did not get a reference to FW series.
I love it when Glowing Blue in the dark.
And I've tried to apply Series with PT filament 5vac CT. I'm doing this to obtain Balance.
Are this a correct?
866's need time to preheat.
for PT HV and PT filaments made separately, as said by .. there should be a time delay for HV.
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.