It's to refrence the heaters to ground,and help reduce hum.
Many times a wire wound "Hum Pot" was used instead,with the wiper to ground,you just adjusted the pot untill the hum was gone (or at it's lowest level.)
Many times a wire wound "Hum Pot" was used instead,with the wiper to ground,you just adjusted the pot untill the hum was gone (or at it's lowest level.)
If I could just add to this, does anyone have a procedure for nulling whilst using discreet resistors? Any idea how far from centre is common and how much noise reduction is expected?
I have seen 100 ohm as a standard value for this, going by that i would say 75 ohm would do exactly the same job.
The 2W rating is fine for 6.3V heaters.
Regards
Craig
The 2W rating is fine for 6.3V heaters.
Regards
Craig
For what it's worth, I have a spec sheet that recommends this. It is for the 46, with a 2.5V filament. According to RCA, the resistance from end to end should be 20 ohms for this device.
The two resistors take the place of a center tap on the winding. If the winding has a center tap, ground it and eliminate the resistors.
If there is a 5v winding intended for a tube rectifier, please do not run 100 ohm resistors to ground from it. They will short out your high voltage.
If there is a 5v winding intended for a tube rectifier, please do not run 100 ohm resistors to ground from it. They will short out your high voltage.
Enzo said:
what if the 5V line for the rectifier heater has a center-tap? do I ground this wire?
Most definitely NOT! Shorting of B+ to ground would occur. If you are using a directly heated rectifier, like a 5U4, take the B+ from the CT. OTOH, if you are using a rectifier with a cathode sleeve, like a 5AR4, tie the CT wire off and insulate it THOROUGHLY.
Eli Duttman said:
I'll be using a 5V4G which seems to work like a 5U4. so I guess I need to insulate that CT wire then. right?
thanks
I use a 5V4G. Pin 8 is a common heater/cathode connection. I use this as the B+ connection, and it also connects to one side of the heater winding. Pin 2 goes to the other side of the heater winding. There's no centre tap. That is all for those pins, and it gives good performance.
Like the 5AR4/GZ34, the 5V4/GZ32 has a cathode sleeve. So, tieing the CT wire off and insulating it is the way to go. Take the B+ from pin 8 of the rectifier's socket.
lndm said:
No, you haven't missed a thing. You and I are on the same page. Pin 8 is THE place to take the B+ from.
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