Comments by "SeanBZA" (@SeanBZA) on "Chornobyl Family 🇺🇦"
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Linkage you are asking about is a universal joint. Cameras would have failed in high radiation mostly because the radiation damaged the semiconductors in the amplifiers for the vidicon tube, the actual tube itself would degrade slower, simply because of the larger mass of the photocathode meaning it would take much more to damage it. You would get ghost images from radiation off the video entering through the housing gap by the lens, but mostly for radiation all you would get was noise as the amplifier transistors got cooked.
Same for the digital logic making the video signal, where ironically a few generation older cameras, all tube based, would have survived for hundreds of hours more, till the radiation finally changed the values of the components enough. Those would have been seriously radioactive then, as you would had made a lot of highly radioactive isotopes of all the metal parts, and would have a lot of noise on the video from the radiation interfering with the actual electrode structures. But they would survive short term, a few days, looking into the most radioactive parts of the reactor, provided you kept them cool enough. But the failed cameras, once removed and cleaned externally, would decay back to background levels in a few months, as the isotopes created from the gamma radiation and neutron bombardment all have relatively short half lives.
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Pretty reliable, once you remember the correct operating condition for the contacts. They run best with 24V across them when open, and 20 to 100mA of current when closed, which helps by keeping the contacts free from oxide, as they wipe across each other, and this make good metal to metal contact. You get a totally different switch, with thick gold contact faces, for low level signals, such as those from the hundreds of thermocouples and platinum resistance thermometers that were used to measure temperature, and the hundreds of bridge type pressure transducers as well.
Those AZ-5 switches look like they break before make, so while you operate there is a brief period where all contacts are open, so as to prevent shorts. Others will be make before break, where you do not want interruption, while say changing the range on a meter.
The mirror galvanometrs are very interesting, with them not only showing up as readout, but also being a simple interface to the SKALA system to be able to input state information without needing complex extra converters, and also associated programming on them as well to set limits. Just built into the existing display, annd an easy way to show if nominal, or which way the deviation is. Likely there is a further phototransistor there that also acts to inform that the lamp has failed, and print it out for a repair operation. 28VDC lamps, run on 24VDC, probably with a series resistor as well, so as to drop voltage to around 22VDC, so leading to greatly increased lamp life.
The type of lamp is classed as prefocussed beam, as the optical path is fixed in the lamp construction, so that in use no further focussing is needed during changing the lamp, as all of them are adjusted in the factory to have the filament in exactly the same orientation and plane, so you simply swap the failed lamp out, and close the panel up.
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@lbochtler Yes the older type tubes had issues with slow response to bright light, as the phosphor got saturated. Backlighting, and then using a black level clamp to restore the video level back to black, removing the offset at the expense of dynamic range, did help a lot. Of course in TV studio use they simply blocked the iris way down, then put in a lot of light ( 10kW plus on a set was minimum, some went as high as 20kW for what was essentially a 2 desk wide area), so as to both have backlighting on the tube, and also limit peak white, so you could expand video level to a point below smearing, but still have a fast response with minimal smear.
Using for CCTV you had more problems, but there again auto iris was welcomed, or manual iris and accept muddy video.
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You can get a custom LCD made in China, which is a product that has dropped in price, though you might have to reverse engineer it, and order 100 of them, but you can always sell the other 95 to recover the cost, fixing other units that used the same display. But as it is likely a 4 digit common backplane display, and those are still common parts, should be easy to find a modern drop in, though you might have to do a little work to make the pin spacing closer, as the modern displays are considerably narrower, so the pins will all need a spacer.
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@wombatperson Soviets used that narrow width flat screw for decades, as they had standardised on it, and it is a lot narrower than the Western version. Same for the connectors, old patterns with the focus on interchange between wildly different age equipment, as they tended to keep equipment in operation for many decades, and not upgrade at all, so long as it still could be serviced and worked.
After all this was a central economy, where even getting a light bulb involved a lot of paperwork, leading to the black market being big in selling blown light bulbs, especially those with visible blackening on the glass, as selling the faulty ones was not frowned on, but they were difficult to get as a consumer new. So buy blown ones on the black market, and simply swap them at the factory, wait a day, then report them as blown, and the factory would change them, of course the electrician or store keeper keeping the blown ones, to sell as used.
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Totally 100% CCCP made, as the same parts, in different grades of quality, were made for the military, and thus the consumer and industrial equipment used the lower grade parts, and after they started doing commercial production they simply kept on making the same parts, using the same machinery. USSR tech was always on the trailing edge in a lot of respects, as they had to both make the machines first, and then were loath to upgrade them to make newer versions. Some parts were utter junk though, especially capacitors, where they routinely used parts designed in the 1930's, when much more modern parts existed, but because the machinery was still working they made the old ones, despite them being shorter lived, and also making poorer quality parts. Got some old Soviet era metal can capacitors that are identical to the 1940's versions, but made 50 years later, and they are as unreliable as the originals were, degrading even when not used. westerm made units updated over the years, to make them much more reliable, and in many cases closer tolerance and better performing at the same time, and also improved material made them much lighter and smaller.
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