The Fine Things are Always Hand Made
Hello all. Hope you are all doing well. I've recently come to own an AW23 chassis. Among the more interesting components of this radio are two "voltage regulator" tubes. Can someone tell me the purpose of these tubes (other than the obvious) and how do they go about serving their purpose.
The two neon VR's are wired in series. They stabilize the working plate voltage of the oscillator tube at about 150 volts, as I recall..
Benefit - Prevents stations drifting as the set warms up (after the first minute or so, once the VR tubes strike (light up).
The VR tubes work by "sending to ground" the excess voltage over the target voltage, which process produces the orange glow of these neon tubes, or the purple glow of the VR-150 used by the Scott Philharmonic and Phantom Deluxe models. If the B+ voltage source to the oscillator tube plate drops below, say 150 volts, the tube goes dark. At normal house voltages, the radio is designed to provide something more than 150 volts, which the RV tube(s) trims to 150 volts.
The radio plays without the VR-tube(s), but not as well. Long lived tube usually.
as Dave noted, gas regulator tubes were quite common in circuits where you need a stable voltage. There were 4 regularly used tubes in the octal era: 0A3, 0B3, 0C3 and 0D3, which regulated voltage at 75, 90, 105 and 150 respectively. The neon lamps Scott used are NE-46 and unless they are broken, they really do not go "bad" since there is no emission. If they light, you are good to go! I like them because they are a fast indication of B+ voltage - tubes dark, go check B+ first.
Thanks to you both for the tutoring. On mine I'm getting about 142 volts at 124 VAC line. I'm even more anxious to get it working to the see the VR's in action.
On a side note, the radio didn't come with a power supply or speaker(s). I have a replacement PS put together and am planning on using the output of the 6C6's as a preamp going to a transistor amp through an audio transformer. If you happen to come across anyone with a PS for sale I would definitely be interested in looking.
The AW-23 radio pair of VR tubes have a great orange color. Glow may be on the top of the electrodes or under.
The VR tube has an auto type two contact base and can be removed, rotated 180 degrees and re-inserted to change where the glow appears.
I like mine to glow on the electrode top surface to show through the holes in the top of the tube shields.