I’m Back! Pilot TV37

[Electronic M]

Originally Posted by jr_tech

Could you post a photo of a “pea pod” cap, please?

jr

Yeah. I don't remember anything of that description. A pic might fire some neurons.

[Chris K]

Originally Posted by jr_tech

Could you post a photo of a “pea pod” cap, please?

jr

Here you go

[jr_tech]

Ah! the “dogbone” caps are ceramic, and mostly last forever.

jr

[Chris K]

Originally Posted by jr_tech

Ah! the “dogbone” caps are ceramic, and mostly last forever.

jr

Good to know. Just ordered a complete complement of resistors. Will replace every one of them regardless of measured value. I’m going to get a full set of new tubes as well…just to be sure.

[Chris K]

Originally Posted by Chris K

Good to know. Just ordered a complete complement of resistors. Will replace every one of them regardless of measured value. I’m going to get a full set of new tubes as well…just to be sure.

Here's an update: What I thought was a vertical deflection issue was not. Somehow, the CRT had been rotated 90 degrees so the vertical was fine...the horizontal was the problem!

Replaced the horizontal amplifier and oscillator tubes but it had little effect. The trimmer cap screws for horizontal size and linearity were seized so I removed the trimmer from the bottom of the chassis, disassembled and cleaned it. When I applied power, this is what I got. Obviously a very long way to go but I have something that resembles a full deflection screen. The Littlefuse diodes came today. Does anyone have any info on how to install one to protect this rare working 3KP4?

[Electronic M]

Originally Posted by Chris K

Here's an update: What I thought was a vertical deflection issue was not. Somehow, the CRT had been rotated 90 degrees so the vertical was fine...the horizontal was the problem!

Replaced the horizontal amplifier and oscillator tubes but it had little effect. The trimmer cap screws for horizontal size and linearity were seized so I removed the trimmer from the bottom of the chassis, disassembled and cleaned it. When I applied power, this is what I got. Obviously a very long way to go but I have something that resembles a full deflection screen. The Littlefuse diodes came today. Does anyone have any info on how to install one to protect this rare working 3KP4?

Install the diode in parallel with the heater of the 3KP4.

[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.

[timmy]

I have a pilot and just picked up a 6.3 filiment transformer and put a resistor in place of the original heater connections so it’s separate should help keep it safe.

[tvdude1]

Have 2 Pilots never had to change a resistor they work well.

[Chris K]

Question about the ballast on this chassis. I can't find any reference of it on the schematic...no resistance values...nothing. It's listed as a miscellaneous part! Am I missing something. I have filament strings now that do not light up. Could a resistor in the ballast be open?

[Chris K]

Originally Posted by Chris K

Question about the ballast on this chassis. I can't find any reference of it on the schematic...no resistance values...nothing. It's listed as a miscellaneous part! Am I missing something. I have filament strings now that do not light up. Could a resistor in the ballast be open?

OK I figured it out and the ballast is fine...Pin 1 to 2 is 10 ohms, pin 2 to 3 is 10 ohms and pin 4 to 6 is 460 ohms. That looks correct on the schematic

[Chris K]

Originally Posted by Chris K

OK I figured it out and the ballast is fine...Pin 1 to 2 is 10 ohms, pin 2 to 3 is 10 ohms and pin 4 to 6 is 460 ohms. That looks correct on the schematic

Well crap, I did it again! I need to learn my lesson with these ancient TVs to go slow and be conservative. I had a picture and was moving along fine and then started replacing components like crazy, didn't stop to check function between 2 or 3 parts, and now I have replaced most of the resistors and caps and I have nothing. A couple of days ago, I powered it up and a 3 ohm resistor that drops voltage from tube to tube in the filament string between the 6AU6 Ratio Detector Driver and the 6AL5 Ratio Detector essentially blew up. The 6AL5 is actually the last tube before the ground in the string on the negative rectified voltage side. But long story short, I'd like to go back to basics and start measuring voltages from jump. The problem is, when powered up, some of these tubes appear to be red plating. My guess is it's excessive filament voltage because parts of the other string are not lighting up. I have seen in a standard TV with a standard CRT, you can pull all of the tubes except for the HV ones and start from there to see if you can get power and then a raster but an electrostatic CRT television is something I haven't dealt with before. I want to be conservative but I don't know where to start the troubleshooting process and I don't want to power the chassis up and sacrifice tubes that are burning hot. Any suggestions as to where I can begin a basic troubleshooting so I can find where I screwed up? I've probably done the wrong thing here and uploaded the radiomuseum schematic. Help!...again!