Zenith Model / Chassis H2437R porthole TV

[E_the_F]

Hi guys! New guy to this site BUT does anybody know where I can find a replacement CRT for my Zenith porthole TV set (Model / Chassis H2437R)
The picture tube in mine is dead 💀 would LOVE to find a replacement! Thanks!

[Electronic M]

Originally Posted by E_the_F

Hi guys! New guy to this site BUT does anybody know where I can find a replacement CRT for my Zenith porthole TV set (Model / Chassis H2437R)
The picture tube in mine is dead �� would LOVE to find a replacement! Thanks!

If you're ever near Milwaukee I have a spare 16GP4 that opperated well enough to make a picture in my Zenith Porthole...I don't ship though so don't ask.

How did you test yours? Have you tested a known good CRT to test your tester? My 16GP4 was stone dead when I first hooked it up to the tester, but came back to life after a couple hours with the heater voltage on the tester set to 8.4V
Many CRTs that have been dormant for years to decades develop cathode poisoning (or sleeping sickness as other collectors call it) the cathode that skirts electrons is a highly reactive metallic compound similar to a getter (element placed in a tube to collect the gas particles that are contaminating the vacuum). The cathode behaves as a getter whenever it is not running and when that happens the gas it's surface collects forms a coating that blocks emission. If you heat the cathode above it's normal opperating temperature and draw a current (as an emissions test or normal opperation will do, either way still assuming you increase heater voltage) and let the CRT sit in that state for 15min-6hours often the CRT will wake up and produce usable emission. After 6 hours if still stone dead you have nothing to loose performing a rejuvenation on it.

Color CRTs waste ~%80 of their emission on the shadow mask (the rest hitting the phosphor and making light), monochrome CRTs waste almost no emission with virtually all emission striking the phosphor....The good-bad emission scale of basically all testers designed to test color CRTs is calibrated for color CRTs....So on a tester that can test color CRTs if a monochrome tests midway up the bad scale it should produce a watchable picture in a working set.

[E_the_F]

Tom,
Thanks so much for the info! Very informative!
A friend of mine has the CRT and is testing the tube. He restored his Porthole Zenith and I assume left the tube on to “cook” for a while but I’ll double check. Thanks again!

[Jeffhs]

Originally Posted by Electronic M

If you're ever near Milwaukee I have a spare 16GP4 that opperated well enough to make a picture in my Zenith Porthole...I don't ship though so don't ask.

IColor CRTs waste ~%80 of their emission on the shadow mask (the rest hitting the phosphor and making light), monochrome CRTs waste almost no emission with virtually all emission striking the phosphor....The good-bad emission scale of basically all testers designed to test color CRTs is calibrated for color CRTs....So on a tester that can test color CRTs if a monochrome tests midway up the bad scale it should produce a watchable picture in a working set.

Until I read your post a few moments ago, I didn't know color CRTs wasted most of their electrons going to the shadow mask, with only about 20 percent actually reaching the CRT phosphors. This makes me wonder why color CRTs are that inefficient. I would think color tubes would be much more efficient than what you mentioned. Since color TVs were much more expensive than b&w sets, I would also think the former would be designed to make a picture at least as bright as the latter, if not brighter. It was probably a good thing, IMHO, that this was never mentioned (in laymans' terms, of course) in color TV advertising; if it had been, I don't think color TV would have been the huge success it was in the US and Canada.

BTW, I had two old color TVs, both Sears Silvertone (Warwick), that made excellent pictures despite their ages (they had been made some time in the 1970s, IIRC). I would never have guessed they both had electron-wasting CRTs. Again, why on earth were color tubes designed to produce much dimmer pictures than b&w ones? Given the prices of color TVs, I would think most people would complain to high heaven if they knew this: "Hey! Why is my color TV picture so much dimmer than my b&w set?"

[Notimetolooz]

Jeff, I think you missed the point. The screens are about equal brightness but the color tube guns have to be worked harder to make up for the efficiency difference.

[old_tv_nut]

Basic geometry. It's called a mask because it masks/hides at least two thirds of the phosphor dots (two out of three) from any one of the electron beams. For three beams and three phosphor colors, the maximum unmasked area is 33%, otherwise electrons from the wrong gun would spill onto the wrong color phosphor. Add some guard band for beam landing errors (purity adjustment), and you end up with about 20% of the mask area being open.

[E_the_F]

OK...we’ve tried everything its definitely dead 💀. Heater is burned out! SO...about a replacement 16GP4... lol anybody have any leads? Thanks!