Engineering question: Tube Camera Survivability

[sdsw4]

So in coupling with my other thread about the M3a, I bring this question for engineers.

In my collection, I have the Sony M3a (being worked on) as well as a similarily aged and even more beat-up HVC-2200.
However, right now, somehow the consumer 2200 is the only tube camera I have that is actually operational. And I bought it partially broken out of a pawn shop.
Debut 8.jpg

Seems like the professional camera should have 100% outlived the consumer camera, but instead the professional camera needs the overhaul while the consumer camera runs fine.
So my question for preserving this hardware is, what exactly determines how a vintage electronic television camera survives as operational for 30+ years? Such as what forms of maintenance, design, use and storage allow some cameras to outlive others?

[Pio1980]

Deleted on review, irrelevant to query.

[old_tv_nut]

Cameras will be subject to the same failure modes as any other old electronics for everything except the pickup tube itself. This all depends on the components used, how stressed they are in the design (voltage/power ratings, heat buildup - you know the drill), amount of use.

The pickup tubes themselves are particularly prone to cathode wear compared to other tubes due to the small cathodes used to get a fine scanning spot. Standard definition tubes will have a longer life than high definition because of the larger cathodes. The longest life is obtained if the tube is fired up at least every three months or so for a few hours of use. This tends to sweep up any gas accumulation.

The first Sony HD Saticons were guaranteed for only 800 hours. In studio use, this would go by quickly. The ones we had in the early BTS camera at Zenith were run much longer than this and still had good performance, but after reaching many multiples of the rated lifetime we retubed the camera as a precaution (at a cost of $85,000).

Side note: the preamp for the Sony HD Saticons was soldered directly to the tube faceplate for minimum stray capacitance. Sony would not sell their proprietary low-noise preamps, but they were already installed at the factory. So, BTS could buy the tubes, but had to unsolder the Sony pre-amps and return them to Sony, and solder on BTS pre-amps.

[ppppenguin]

A problem that's affecting a few earlier camera tubes is helium ingress. The glass is permeable to helium and despite the low concentration in the air, there's a density gradient across the glass.

The beam travels a long distance at low velocity so even a farily small amount of gas will cause trouble.

[old_tv_nut]

Originally Posted by ppppenguin

A problem that's affecting a few earlier camera tubes is helium ingress. The glass is permeable to helium and despite the low concentration in the air, there's a density gradient across the glass.

The beam travels a long distance at low velocity so even a farily small amount of gas will cause trouble.

Yep. That's supposed to be reduced by occasionally firing them up. I don't think I knew it's specifically helium, but that makes sense.

[ppppenguin]

I can't see how firing up te tube will make any difference to the helium. It will help with the cathode which often seems to become "sleepy" (for want of a better word) when not used. Many of us have seen CRTs that look bad when first switched on but cheer up after an hour or so.

[sdsw4]

That explains why my Samsung "thin" HD CRT looked really awful when I pulled it out of the grave, aka my basement after a few years but looked much better after an hour of use.

Of course nothing will fix the deflection flaw, but still a damn good TV.

[old_tv_nut]

Originally Posted by ppppenguin

I can't see how firing up te tube will make any difference to the helium. It will help with the cathode which often seems to become "sleepy" (for want of a better word) when not used. Many of us have seen CRTs that look bad when first switched on but cheer up after an hour or so.

I am only relaying the words of the camera manufacturer's rep: "gas."
Whether this was helium or something else, or was another effect, I can't say, but the connotation was that degradation would be permanent and worse with longer periods of disuse, not reversible like cathode "sleepiness." Whatever was going on, it was confidently stated that periodic use helped extend the life of the tubes.

[ARC Tech-109]

One thing that contributes to the gassing of imaging tubes is the soft seal used to bond the target to the cylinder, this is not a glass to glass bond as the heat would destroy the target composition so instead its a polymer and they do deteriorate over time.