All of these booster damper tubes are glass-envelope power diodes very suitable for use in audio amplifiers and ham radio linear amplifiers as a half-wave B+ rectifiers and can withstand few hundreds of mAs. Their cathode to filament isolation is extremely high, allowing the use of a common heater winding for all the tubes. Decades ago they have been originally intended for black&white & color TVs booster-diode service, so they are very robust and reliable and they have long warm-up time, longer than common rectifiers like GZ34 5AR4 5V4G 5U4 …
My recommendation is to not use them with more than 85% of maximum average plate current for noval rectifiers and no more than 65% for magnoval rectifiers. Also don’t exegarate with input capacitor! I use EY500 in power supplies which deliver 1500V!
I have seen them used like a slow start in many silicon rectifier bridges, they are just simply connected in serial after electrolytic capacitors.
EY88 6AL3 Vf=6,3V If=1,55A Va=550V/250V Ia=550mA/220mA Pa=5W
EY500A 6EC4A Vf=6,3V If=2,1A Va=7000V/5600V Ia=1000mA/440mA Pa=11W
PY500A 42EC4A Vf=42V If=0,3A Va=7000V/5600V Ia=1000mA/440mA Pa=11W
Left to right: EY88 6AL3 EI Yugoslavia Philips code; EY88 6AL3 boxes of 100 pcs; EY500A EI Philips; PY500A boxes of 50 pcs; EY500 boxes of 50 pcs; PY500 EI Yugoslavia Philips licence
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