I’m Back! Pilot TV37

[nasadowsk]

Was it a situation that the 3KP4s were so flaky, and the 3KP1 was the only replacement, or were a lot of these shipped from the factory with 3KP1, because the 3KP4 wasn't in good supply?

[Electronic M]

Originally Posted by nasadowsk

Was it a situation that the 3KP4s were so flaky, and the 3KP1 was the only replacement, or were a lot of these shipped from the factory with 3KP1, because the 3KP4 wasn't in good supply?

Theses never shipped with P1 tubes that I know of. This set is the only application of the 3KP4 AFAIK so there weren't tons of replacements laying around even back then. The TV37 was the cheapest pre-built TV on the market when it was sold and had the smallest screen you could get...Short of portable applications that set probably wasn't desirable enough to put a CRT in once it was 5 years old.

I also have seen first hand a power rectifiers tube in one of these sets fail and pop the CRT heater... I'm just glad it wasn't my set.

[Jeffhs]

Originally Posted by Electronic M

I also have seen first hand a power rectifiers tube in one of these sets fail and pop the CRT heater... I'm just glad it wasn't my set.

Until you mentioned it, I had never heard of the rectifier tube in a TV fail in such a way as to open or otherwise damage the CRT filament, unless it was somehow possible for a defective rectifier tube to put entirely too much voltage on that filament. I would think if the LV rectifier tube were defective in any way, the worst that could possibly happen would be the set's line fuse or the house fuse would blow. The LV supply in these Pilot TVs must have been built much differently from that in most sets of that time.

I don't know what type CRT was used in the Pilot TVs (I've never seen or owned one), but I am thinking the CRTs in those sets is very rare, with replacements almost impossible to find except from a junker. The 3KP4 CRT seems to fit that category. Until I read your post, I personally had never heard of such a CRT being used in commercially-available televisions. Your set must have been made in the days when television was very new, which would have been in the late 1940s.

[Jeffhs]

Originally Posted by Electronic M

Theses never shipped with P1 tubes that I know of. This set is the only application of the 3KP4 AFAIK so there weren't tons of replacements laying around even back then. The TV37 was the cheapest pre-built TV on the market when it was sold and had the smallest screen you could get...Short of portable applications that set probably wasn't desirable enough to put a CRT in once it was 5 years old.

I also have seen first hand a power rectifiers tube in one of these sets fail and pop the CRT heater... I'm just glad it wasn't my set.

Why would the CRT heater open if the LV rectifier tube failed? I wouldn't have thought an LV rectifier failure would have anything to do with the filaments in any tube in the TV, unless the failure somehow caused an abnormal increase in heater voltage; even then . . . I just cannot imagine how a failure like this could have caused an increase in CRT heater voltage, or of any other tube in the set.

BTW, it will not be easy to find a replacement for a 3KP4 CRT. This TV was made in the late 1940s, when television was just starting in North America. A new tube will almost certainly be impossible to find. Your best bet would be to try to find a 3KP4 in a junked set, if possible.