I haven't seen this subject brought up for a while. However, I have
heard of counterfeits showing up at flea markets and sometimes exported.
Since Eimac left the glass tube business, there have been instances of
Chinese tubes with Eimac and Amperex logos and cleaverly copied markings
or labels, yellow Eimac style boxes, etc.
Listed are common tubes and their counterfeit clones:
3-500Z EIMAC. Late issue Eimac will have the Eimac logo imprinted
on the grid shroud. Eimac will usually have the serial number engraved
with vibrating pencil on the shroud. Chinese tubes will have their
date code & serial number stamped along the edge or on top of shroud
(first two digits indicating year of manufacturer).
3-500ZG EIMAC. Same as 3-500Z, only with graphite anode.
4-400 series Amperex: Counterfeits use the "slip-on" anode terminal
with set screw. Only Amperex has the terminal fussed through the glass.
I am curious if anyone on the reflector has run across these bogus tubes.
Merit W6NQ
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