This article provides examples of GE (KEN-RAD) manufactured tubes.
GE was one of the most prolific tube manufacturers in US history, and many companies sold GE tubes repackaged under their own brand name. The GE factory EIA code number is “188″ and proves GE was the true manufacturer, although there are a few rare exceptions to the “188” rule. Here are several examples:
This photograph shows examples of GE/Ken-Rad manufactured tubes with 188 codes. From left-to-right: Magnavox, Zenith, Admiral, Ken-Rad.
It is amusing to read on the Admiral tube “Replace only with a genuine Admiral tube.” Marketing hype at its finest, because there were no Admiral-manufactured tubes. In this example, it was a GE tube.
Here is a rare instance where the 188 code was printed on a 6SN7GTB tube, but the real manufacture was Sylvania. This photo compares a well-known Sylvania design of 6SN7GTB black plates audio tube, 1960’s vintage, which has printed into the glass “6SN7” above “GTB”. The GE tube on the left of the photo is without any doubt Sylvania-manufactured, even though the tube was silkscreened “188-5” and GE boxed and branded. This is a situation where experience provides the real answer, and the 188 oem code was misleading.
Another example would be Amperex “111” marked tubes. Most of the inventory that I have seen were obviously GE manufactured.