Early Philco tube date codes - Printable Version

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Early Philco tube date codes - Tubesforme - 03-01-2016

I know that prior to 1930, Philco branded tubes were manufactured by RCA. Then Philco changed over to Sylvania manufactured tubes, branded Philco. I know all of the EIA codes and meanings of date codes after about 1940. However I am curious about the 1930's Philco branded tubes manufactured by Sylvania. I have many different tubes of this type, all four or five pin types. The codes are like these examples: K1, F0 and OB. I have never come across any info on these two digit codes. Can anyone tell me the years this type of code stands for as well as maybe the month of manufacture? Nothing to loose sleep over, just interested, that's all. Thanks guys.

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RE: Early Philco tube date codes - Ron Ramirez - 03-01-2016

Prior to 1930, there were no Philco branded tubes.

I have a 1929 ad somewhere with Walter Holland, Philco's Chief Enginner at the time, extolling the virtues of RCA Radiotrons.

In 1930, by which time relations between RCA and Philco had taken a turn for the worse, Philco made a deal with Hygrade and Sylvania to supply tubes instead of RCA. The deal was sweetened by Hygrade and Sylvania agreeing to put Philco's name on the tubes.

I have a sheet with the 1930-1934 date codes somewhere. I just don't know where right now. That code used twelve letters which stood for the twelve months of the year.

Around 1935 or so, Philco (Sylvania) switched to a simpler date code - O P U S - in which 5O (or O5) stood for first quarter, 1935; P5 = second quarter 1935; U5 = third quarter 1935; S5 = fourth quarter 1935.

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RE: Early Philco tube date codes - Tubesforme - 03-02-2016

(03-01-2016, 10:41 PM)Ron Ramirez Wrote:  Prior to 1930, there were no Philco branded tubes.

I have a 1929 ad somewhere with Walter Holland, Philco's Chief Enginner at the time, extolling the virtues of RCA Radiotrons.

In 1930, by which time relations between RCA and Philco had taken a turn for the worse, Philco made a deal with Hygrade and Sylvania to supply tubes instead of RCA. The deal was sweetened by Hygrade and Sylvania agreeing to put Philco's name on the tubes.

I have a sheet with the 1930-1934 date codes somewhere. I just don't know where right now. That code used twelve letters which stood for the twelve months of the year.

Around 1935 or so, Philco (Sylvania) switched to a simpler date code - O P U S - in which 5O (or O5) stood for first quarter, 1935; P5 = second quarter 1935; U5 = third quarter 1935; S5 = fourth quarter 1935.

Thanks Ron, I hope that you come across the sheet at some time. I always follow the Phorum and so if it is posted on the Phorum, I will see it. You have a great and very helpful site here.

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