First frame grid tube
I believe that Bell Labs (part of AT&T) invented the frame grid tube. The 404A pentode came out in 1948, intended for IF amplifier use in microwave links. There is an article describing it in the Feb. 1949 issue of the Bell Labs Record, page 59 (available at https://www.americanradiohistory.com/Archive-Bell-Laboratories-Record/40s/Bell-Laboratories-Record-1949-02.pdf). The article claims that the gain-product bandwidth was improved 70% over the earlier 6AK5. Frame grid construction was also used on the 416A (1948), 417A (1948), and later high-performance triodes and pentodes.
- John Atwood
I believe that Bell Labs (part of AT&T) invented the frame grid tube. The 404A pentode came out in 1948, intended for IF amplifier use in microwave links. There is an article describing it in the Feb. 1949 issue of the Bell Labs Record, page 59 (available at https://www.americanradiohistory.com/Archive-Bell-Laboratories-Record/40s/Bell-Laboratories-Record-1949-02.pdf). The article claims that the gain-product bandwidth was improved 70% over the earlier 6AK5. Frame grid construction was also used on the 416A (1948), 417A (1948), and later high-performance triodes and pentodes.
- John Atwood
Perhaps it was Europe which pioneered the use of frame grids in domestic receiving valves? Maybe Philips developed a way to make them more cheaply? There appears to be no US counterpart to the EF183/184 widely used in TV sets in Europe.
I know they have US names too, but were they ever used in a US-designed TV? Or actually made in America? US practice seemed to use non-frame-grid pentodes with slightly lower gain in their TV IF strips.
Of course, we have the usual problem that manufacturers would often pretend (or, at least, strongly hint) that innovations were invented by them when this is not the case. They would forget to say that their 'new' valve was actually a copy of something developed by someone else a few years earlier.
Of course, we have the usual problem that manufacturers would often pretend (or, at least, strongly hint) that innovations were invented by them when this is not the case. They would forget to say that their 'new' valve was actually a copy of something developed by someone else a few years earlier.
Yes, I also can't tell for sure whether these 6EH7's/6EJ7's are of original US make or just relabeled European valves.
Best regards!
Best regards!
The American tube companies initially imported the 6EH7/EF183 and 6EJ7/EF184, but later as they were used by TV manufacturers, started making their own. In particular, Sylvania, RCA, and GE made them in America. BTW, the country of origin is always marked on American tubes, or at least is supposed to be.
Zenith was one of the largest color TV manufacturers in the 1960s and they extensively used the 6EH7 and 6EJ7. In 1963, RCA came out with the 6JD6 and 6JC6, which are electrically very similar the the 6EH7 and 6EJ7, respectively, and were widely used. I just cut open a 6JC6, and it is a frame-grid tube.
However, American tube companies continued to make conventional-grid pentodes for TV IF amplifiers, such as the 6EW6 and 6GM6. These were used in some color TVs, but were more used in B&W TVs.
The exchange rates and trade policies in the 1960s made importing tubes from Europe and Japan attractive in America, which is why you see so many Zenith-branded 6EJ7s "made in Holland" (i.e. Philips), despite the presence of American-made 6EJ7s. Raytheon completely shut down their receiving tube production line in America in the early 1960s and imported all their tubes from Japan (Toshiba, I think). As the other American tube producers shut down their production lines in the 1970s and 80s, they imported tubes from their foreign licensees, so you started to see tubes from Brazil, Mexico, Korea, and Taiwan, as well as Japan and Europe.
- John Atwood
Zenith was one of the largest color TV manufacturers in the 1960s and they extensively used the 6EH7 and 6EJ7. In 1963, RCA came out with the 6JD6 and 6JC6, which are electrically very similar the the 6EH7 and 6EJ7, respectively, and were widely used. I just cut open a 6JC6, and it is a frame-grid tube.
However, American tube companies continued to make conventional-grid pentodes for TV IF amplifiers, such as the 6EW6 and 6GM6. These were used in some color TVs, but were more used in B&W TVs.
The exchange rates and trade policies in the 1960s made importing tubes from Europe and Japan attractive in America, which is why you see so many Zenith-branded 6EJ7s "made in Holland" (i.e. Philips), despite the presence of American-made 6EJ7s. Raytheon completely shut down their receiving tube production line in America in the early 1960s and imported all their tubes from Japan (Toshiba, I think). As the other American tube producers shut down their production lines in the 1970s and 80s, they imported tubes from their foreign licensees, so you started to see tubes from Brazil, Mexico, Korea, and Taiwan, as well as Japan and Europe.
- John Atwood
OK. I have just seen a datasheet for Sylvania 3EJ7, 4EJ7 and 6EJ7. 6EJ7 could in theory be an import but the first two would not have been much use in Europe so that confirms what you say.
...ditto Valvo, a Philips subsidiary in Germany, in their Handbuch Spezialröhren (special quality valve handbook) from 1970. I'm quite convinced that any major European tube manufacturer made E83CC's - with the exception of Telefunken, whose SQ valve was the ECC803S, quite another beast based on the E88CC, but with ECC83 data.
Best regards!
Best regards!
I think there is always the possibility they were delivered in bulk packs, and something got lost in translation when they were marked up for distribution. There are other cases with tubes with mispellings on them. I suppose the proof of the pudding is in the eating.