EL519 6KG6 6KG6A EI Yugoslavia, made in 1984 on Philips machines and with Philips materials. They are true triple mica construction. These are specialy selected batch for export, without EI signs printed on tubes, they could be seen rebranded Philips, Siemens, Valvo and Telefunken during late 80s. Perfect matching possible!!! Original factory service pack with 50 tubes in each box.
“ADW” Philips type code for EL519. Under is Philips code for Elektronska Industrija Nis, and “4” year code, 1984 Golden era of EI factory.
This tubes are much, much better than same EI tubes from 90s. I spoke with old engineer from EI factory and he told me that with complete Philips line for EL509 / PL509 tubes tons of original Philips materials came with line too. Later when those quantities were gone, quality was worse and worse. Post war (1991) tubes show big variation in characheristics and don’t last for decades like old ones.
Triple mica spacers clearly visible on photos above.
This tubes are very scarce these days, but 30 years ago you could buy them everywhere and they’ve been used everywhere! In almost all color TV sets, ham HF amplifiers, CB linears (Zetagi BV131), ham rigs, pirate broadcast equipment. During 80s, in my childhood, it was our favorite tube for MW band, I personally used it with 1.0 – 1.8 kV on plates, but some of my friends put 2-2.5 kV on plates!!! More details here: 1.7MHz AM transmitter with 3xEL509/ EL519, pirate AM transmitter with one EL509 / PL509 .
During 80s and 90s many OTL, PP and SE amps were constructed with EL509 6KG6. One of the most famous amps using EL509 / EL519 is Tim De Paravicini EAR859 / EAR869 in ingenious enchanced triode mode!