Hi,

I am looking for the production year of early CRTs. I know that the 5AP4 and the 5BP4 were produced already as early as 1939. But when were the following CRTs produced?

5FP4
7BP4
7DP4

Kind regards,
Eckhard

Hi Eckhard,
Tube Lore shows the following:

5AP4 - April 17, 1939
5BP4 - May 1, 1939
5FP4 - August 1, 1942
7BP4 - June 30, 1945
7DP4 - April 15, 1946

The RMA-EIA only started assigning registrations of CRT's in April of 1939 with the 5AP1/4. The earlier versions of these crts; 5BP4 AKA 1802 and 5AP4 AKA 1805 don't show an introduction date however most of these 1800 series crt's were introduced in the mid 1930's.

Darryl

Hi Darryl,

that's great!

Thank you very much!

I didn't expect that these tubes are introduced so early.

Kind regards,
Eckhard

Many of the early 5BP4's I've seen are dual marked 1802/5BP4, so this must have been during the transition time to the RMA-EIA markings. I can't find any data on when the various 1800 crt's were introduced, but all the 900 series ones are shown in the 1935 RCA CRT Manual, and some 1936 literature shows the 1800 and 1801 crt's.

Darryl

Um I have a Question here, My Question is Wat Date is the 7JP4 Picture Tube came out??? Because it looks loke an Oscilloscope tube.

I understand that it has been used by several television Manufacturers
hope to hear obout it.

thanks

Um I have a Question here, My Question is Wat Date is the 7JP4 Picture Tube came out??? Because it looks loke an Oscilloscope tube.

I understand that it has been used by several television Manufacturers
hope to hear obout it.

thanks

Same source - Sept 20, 1950

Chuck

Um I have a Question here, My Question is Wat Date is the 7JP4 Picture Tube came out??? Because it looks loke an Oscilloscope tube.

I understand that it has been used by several television Manufacturers
hope to hear obout it.

thanks

September 20, 1950

(Chuck, you beat me by 1 minute :) )

Same source - Sept 20, 1950

Chuck

What am I missing here? the Motorola Vt71 (which uses a 7JP4) was likely introduced in 1948 (Sams set 55 folder 16... 2/49)

jr

What am I missing here? the Motorola Vt71 (which uses a 7JP4) was likely introduced in 1948 (Sams set 55 folder 16... 2/49)

jr

Good point. This is the date that is listed in Tube Lore. The dates Ludwell gives are supposed to be the dates the numbers were registered with the RMA. I don't think they would have commercially produced the tube before registering it, so perhaps this is a typo?

Darryl

It could be a typo as the 7GP4, the predecessor of the 7JP4, is listed as April 15, 1946.

Chuck

So why can't I find an 1800-series equivalent lised for the 7AP4? It has a 5-pin base versus the 6-pin for the 9AP4, 9CP4, 12AP4 and 12CP4. All 5 have the 2.5-volt heater.

BTW, a used copy of Tube Lore fetches $75-$165 on Amazon, with new copies at $24.95, and $17.95 on the EHT.com website.

According to Peter Kellers THE CATHODE RAY TUBE, the 7JP4 was introduced by RCA in 1947. He also indicates the 7AP4 was introduced in 1940. Maybe there was no 1800 series equivalent number for the 7AP4...?

Just talked to Peter Keller... He says:

7JP4: Tentative RCA data sheet 8-47, Registration Sept. 12, 1947
7JP1: Tentative RCA data sheet 1-50, Registration Sept. 28, 1950

"not uncommon for different Phosphor types of the same tube to have different registration date."

"doubtful that an 1800 series 7AP4 existed"

Tube lore says:
7JP1: Sept. 20, 1950

jr

Tanks for the info, gents! Now if I ever run across one...