Russian equivalents reference lists 5C3S as equivalent to both 5U4G and GZ31 — similar full-wave rectifier but directly heated, different characteristics
Max DC Output Current (total, not per-anode)Max DC Output Current225mA
Notes
The GZ31 is the Mullard/Philips designation for a full-wave rectifier. The 5AS4A is the American RETMA equivalent.
Indirectly heated cathode with 5V heater. Sams lists 5U4G as a substitute.
Soviet equivalent 5C3S (5Ц3С) covers both 5U4G and GZ31 according to the Russian equivalents reference.
Peak Inverse Voltage is not explicitly stated in the Mullard/Philips GZ31 datasheet; PIV=990 V is derived from the standard full-wave capacitor-input relation PIV = 2 × √2 × Va_max (350 Vrms). Matches the convention used for AZ12, UU4, UU5, EZ41 in this repo.
Vdrop = 50V per references/rectifier_reference.json entry for 5AS4-A ('improved 5U4') — GZ31 is the Mullard/Philips designation for this same indirectly-heated 5V/2A octal rectifier (description in this file confirms the 5AS4/5AS4A equivalence).
Pin Layout — Octal
1No Connection
2Heater
3Anode 1
4
Socket-Compatible Tubes ⚠ Not electrically compatible