Electrically related Philips high-current rectifier but uses P8A 8-pin side-contact base — different socket, not pin-compatible
CV1264
B4 base, 4V heater but 3.4 A filament (vs AZ50's 3 A) — draws more heater current, not a safe drop-in in circuits with fused 3 A heater supply
RGN4004
B4 base, same function, but 4 A filament (vs AZ50's 3 A) — Telefunken/Siemens designation for a higher-rated variant; incompatible heater transformer winding
Electrical Specifications
Absolute Maximum
Anode Voltage (max)AC Voltage per Plate (max RMS)500V
Voltage Drop (typical)Forward Voltage Drop (read from AZ50 Ia/Va curve at 150 mA per plate)24V
Max C-input Filter CapacitorMax C-input Filter Capacitor (at 2×500 Veff)64
Notes
Directly heated (filament cathode) — observe heater warm-up time before applying B+. Filament is heated by AC per the datasheet ('direct by A.C.').
Operating conditions from the Philips datasheet (3 rated voltage columns): at 2×300 Veff: Io_max=300 mA, Rt_min=100 Ω, C_max=16 µF; at 2×400 Veff: Io_max=275 mA, Rt_min=150 Ω, C_max=32 µF; at 2×500 Veff: Io_max=250 mA, Rt_min=200 Ω, C_max=64 µF. Idc_max=300 mA is the rated DC output (at 2×300 V); Va_max=500 V and C_max=64 µF are from the 2×500 V column.
Peak Inverse Voltage is not explicitly stated in the datasheet; PIV=1414 V is derived from the standard full-wave relation PIV = 2 × √2 × Va_max (500 Vrms). Matches the convention used for AZ1, AZ4, AZ11, AZ12 in this repo.
Vdrop=24 V is read from the single-plate I/V characteristic (Philips AZ50 datasheet page A, Ia vs Va, 0–600 mA / 0–80 V) at 150 mA per plate (= Idc_max 300 mA / 2 for full-wave). The datasheet does not state a discrete Vdrop value.
The CV1264 (GEC/Mullard) and FW4/500 are listed by Radiomuseum.org as 'normally replaceable — slightly different' for the AZ50. Both use the same B4 base but draw 3.4 A filament current vs the AZ50's 3 A — they will stress a heater supply designed for 3 A and should not be treated as drop-in replacements without verifying the heater supply rating.
The RGN4004 (Telefunken/Siemens) appears on the same B4 base with a 4 A filament — it is a higher-rated variant, not pin-compatible in circuits designed for the AZ50's 3 A heater.
Pin Layout — B4
1Anode 1 (Plate 1)
2Filament
3Filament
4Anode 2 (Plate 2)
Socket-Compatible Tubes ⚠ Not electrically compatible