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- Joined: Thu 05/30/19 7:34 am
Early Polam EL84 had slits, because they were made to Russian specifications. Because Polam was taken over by Philips, EL84 produced after the takeover were to 6BQ5 pattern.
For some reason the Philips group used the 6BQ5 design for most of their later production (inc.Mullard) rather than their earlier design, which is what the Russians used exclusively. The 6BQ5 design was originally from Sylvania. The Russians licensed many designs from RCA. RCA licensed the EL84 from Philips, so the Russian 6p14p tubes are closer to original Dutch design EL84 than the Philips-made Polam.