←back to thread

The biggest CRT ever made: Sony's PVM-4300

(dfarq.homeip.net)
235 points rbanffy | 6 comments | 21 Jun 24 22:22 UTC | HN request time: 0.214s | source | bottom
Show context
MenhirMike ◴[22 Jun 24 21:33 UTC] No.40762400[source]▶
I'm kinda curious if CRT technology advanced to the point where a TV like that would've been possible at a better weight and price tag? I assume that CRT technology development stopped decades ago, but could we have e.g., replaced the heavy glass with some plastic-like material to save weight without compromising the picture? And are there any heavy components in the mechanism itself (Coils, Magnets?) that would have had alternatives?

I know it's just theorycrafting, but I do wonder what kind of CRT someone could've created if it wasn't for market economy forces.

replies(7): >>40762471 #>>40762611 #>>40762862 #>>40762908 #>>40763349 #>>40763829 #>>40764554 #
1. cesaref ◴[22 Jun 24 21:43 UTC] No.40762471[source]▶
I imagine much of the weight is for the tube to be strong enough to hold the vacuum without shattering. As the screen area increases, you need stronger electron sources, and higher HT to get the electrons to the phosphor. I think small 14 inch trinitrons are already using 20-30kV so I imagine the power supply and associated HT stuff will be quite scary in these larger sets.

There are all sorts of complex magnet arrangements to tune the beam to stay in focus across the image area, i don't know how that will scale with size, but it's probably more of a complexity when assembling the sets to calibrate the tubes.

replies(1): >>40764081 #
2. refurb ◴[23 Jun 24 02:03 UTC] No.40764081[source]▶
You’d be surprised how little glass is needed to be strong enough to withstand a near perfect vacuum.

I worked in a lab where we routinely held a few micro-torr of vacuum, which is about the limit for mechanical pumps. Cathode ray tubes are typically thousands or tens of thousands higher pressure.

We ran 1/4” wall thickness glass even in large flat stretches without issue.

I’m guessing the weight of large cathode ray tubes are more for durability than need for the vacuum inside.

replies(3): >>40764767 #>>40765450 #>>40765952 #
3. ssl-3 ◴[23 Jun 24 04:22 UTC] No.40764767[source]▶
How much did the flat sections bend or deflect under vacuum?
4. Karliss ◴[23 Jun 24 07:34 UTC] No.40765450[source]▶
That's a bit misleading the level of vacum might differ by factor of 10000, but most of the force is still coming from atmosphere. For overall mechanical strength it doesn't matter that much if its 0.99 or 0.99999999999 atmospheres of pressure difference, temperature and other wheather changes are probably causing much bigger change in force applied to glass.
replies(1): >>40767001 #
5. guenthert ◴[23 Jun 24 09:17 UTC] No.40765952[source]▶
Living room tv sets need to be child-save, unlike lab equipment.
6. willis936 ◴[23 Jun 24 12:35 UTC] No.40767001{3}[source]▶
I don't think it's that misleading. At the end of the day you need a 14.696 psi negative pressure vessel. That isn't very dramatic. If you can confidently make something that works to 14.696 psi then you can be confident it will work at 14.65 or 14.5 psi.

The meat of the comment is that you don't need much material to withstand Earth's atmosphere compared to pressure vessel. It's a common misconception for folks who don't work with vacuums.

Having carried my share of heavy CRTs I can share that most of the weight is in the front glass. It needs to support the phosphor wire mesh and withstand the pokes and stabs of the world while not compromising the fragile thin-walled neck.