The CV1837 (commercially the 6B7) is for parallel heater based mains receivers. The 2B7 differs only in that it has the original American standard AC heater of 2.5 Volts.
The pentode could be used as the final IF amplifier with the diodes as detector and AGC rectifier or it could be used with the pentode as first AF amplifier. The vari-μ nature of the pentode suggests use as an IF amplifier as does the control grid connected to the top cap.
For a low cost set for local reception a pentagrid converter the 6B7 and a high sensitivity output valve would be the probable line-up.
The left part of the label and the RCA logo.
The right side of the label.
The pentode at the top with the two diode rod anodes within the screening box below. The screen is connected to the cathode.
The tape connecting the screen to the round cathode. The heater can be seen to be twisted to minimise hum.
The classic envelope is 38 mm in diameter, and excluding the UX7 base pins is 98 mm tall.
