We’ve found an old tube camera in the vault of a decommissioned bank branch – the owner gave it to us. We were thinking of setting the camera up in our showroom connected to a CRT monitor just to demonstrate performance differences.
The thing is we don’t know anything much about them – no one here has ever seen a tube camera before, much less serviced one. What should we keep an eye out for when trying to recommission?
A: Filament burnout is one of the big problems with tube cameras. In the past a tube tester would be used to test the state of tube but even without a tester, it’s possible to establish trouble. If the filament goes, you’ll see no orange glow at the top of the tube and the tube will be cold. Should the tube be surrounded by a purple glow, it’s leaking. Tubes may also have trouble with shorts in resistors and capacitors which would render them inoperable.
There are still Vidicon tubes for sale on the internet for trivial amounts of money. These were made by the likes of RCA, GE and Sylvania. If you set up a tube camera with a CRT screen you’ll probably be surprised by the contrasty, sharp performance. Resolution in PAL is 576 lines, which sounds low, but when displayed in 4 x 3 will give good detail. Even in tough light you’ll see none of the amplification noise, pulsing, smudginess or blurring common with low cost IP cameras. Tube cameras use a sort of shrunken CRT process to create image streams so there are no digital artifacts in their video streams.
You’ll probably need to tidy up the lens as well – something like a lens pen might be fine for the inner element but you might need to break out the isopropyl alcohol if the front element is filthy. Try not to rub too hard especially with a synthetic cloth or you’ll damage the lens coating.
Finally, if you’re showing a tube camera to a client, try to avoid having them look at an adjacent IP camera image stream of the same scene. The complete lack of latency is likely to be disarming.
* Propeller heads can take a look at the dissection of a Vidicon tube camera here.