Data: MediumMedium quality — at least 60% of universal parameters and pins are present, but some key data is missing. Verify specific values against datasheets before critical use.
Same B4 base and 7.2V heater DHT triode, listed as similar with differences — pin functions require verification before substitution
Electrical Specifications
Absolute Maximum
Anode Voltage (max)Anodenspannung max440V
Anode Dissipation (max)Anodenbelastung max24W
Typical Operating
Anode Voltage (typical)Anodenspannung (typical)350V
Grid 1 Bias VoltageGittervorspannung-19V
Notes
Filament voltage stated as 7.5 V in the RV218 Telefunken datasheet; the RV258 datasheet (same book, adjacent page) states 7.0 V for the identical tube. Reference indexes list 7.2 V. The discrepancy likely reflects rounding — both tubes operate from the same nominal ~7 V filament supply.
Maximum ratings are Va=440V and Pa=24W. The datasheet explicitly states that for higher loadings (Va >440V or Pa >24W), the RV218 must be replaced by the RV258.
Extensively used in transmitter service. When paralleling multiple tubes, the datasheet warns of a risk of self-oscillation at ultra-short (UHF) wavelengths.
A special grid construction prevents 'Durchstoßen' (grid emission / secondary emission breakthrough), a known failure mode in early DHT power triodes.
Amplification factor mu = 1/D = 1/0.14 ≈ 7; anode resistance ra derived as mu/gm = 7/0.002 = 3500 Ω (not explicitly stated in datasheet).
Codewort (factory test code): nsyit.
Pin Layout — B4
1Filament (+)
2Anode
3Control Grid
4Filament (−)
Socket-Compatible Tubes ⚠ Not electrically compatible