Who’s Afraid Of A CRT?

Older consumer electronic devices follow a desirability curve in which after they fall from favour they can’t be given away. But as they become rarer, they reach a point at which everyone wants them. Then, they can’t be had for love nor money. CRT TVs are now in the first stage, they’re bulky and lower-definition than modern sets, and thus thrift stores and dumpsters still have them in reasonable numbers. To retrogamers and other enthusiasts, this can be a bonanza, and when he saw a high-end late-model JVC on the sidewalk [Chris Person] wasted no time in snapping it up. It worked, but there were a few picture issues, so he set about fixing it.

The write-up is largely a tale of capacitor-swapping, as you might expect from any older electronics, and it results in a fine picture and a working TV. But perhaps there’s another story to consider there, in that not so many of us here in 2024 are used to working with CRTs. We all know that they conceal some scary voltages, and indeed, he goes to significant lengths to discharge his CRT. It’s worth remembering though, that there’s not always a need to discharge the CRT if no attempt will be made to disconnect it, after all the connector and cable to the flyback transformer are secured by hefty insulation for a good reason. It’s a subject we’ve looked at here at Hackaday in the past. You could argue that, in some ways, newer TVs are harder to get into than these old CRTs.

25 thoughts on “Who’s Afraid Of A CRT?

  1. I’m a long way from that point mentioned. I have all sorts of retro stuff repaired and in working order, from 1950s valve/tube radios to 1970s hi-fi to 1980s home computers, but the one thing I do not miss is CRTs and their bulk, weight and scary voltages and failing line output transformers.

    That said, I must admit a PDP 8 outputting to a flat-screen terminal would be just wrong. Hmmm…not quite sure where that point is for me!

  2. I had a number of the semi-flat 21″ Viewsonics, IBM and Sony branded units that I was cueing up give to a fellow Cragslister. A family emergency resulted in most of them getting left outside in the rain for quite a while, so I ended up having the city haul them away. sigh..
    I kept wondering what nifty materials that I may regret simply sending to the recycling grinders.
    Two of them powered up were as good as a portable heater in the room though, a bit overwhelming in the summer time.

  3. Pre-1980s TVs are easy to fix. Just check where the smoke is coming from.
    1980-2000 TVs are very hard to fix, if you get somewhat lucky they might give you a blink code and if you get VERY lucky you might even find a blink code list after half an hour of Googling.
    2000-2005 TVs are easy, just change the bulging caps in the power supply.
    2005-2015 TVs are hard, they just break for no apparent reason. Don’t use them for a few years, they’re dead even though all the voltages are present and look good. Won’t even turn on. No blinkies either.
    2015-now TVs are easy, just take the LCD panel apart (which is not as hard as you’d expect, but good luck keeping dirt or dust from getting into it) and find and replace the faulty backlight LED.
    Now-20xx TVs will be hard because they require certain magic Servers to be online.

    1. All TVs are secretly computer monitors now, so you may as well get a giant monitor that only functions as an HDMI device and has no streaming shitware on it at all.

      And then use 34 separate completely legit paid streaming websites on your connected computer (totally not installing ublock origin and going to a website called something like myfreemoviesrussia with a domain extension from Namibia)

      1. TVs should only be computer monitors. Shoever thought that they also needed to have a (linux usually, but no fault of linux’s) computer embedded into a monitor deserves a thorough and vigorous spanking.

        1. Nah, the thing with a TV is that it should also decode various sources you don’t need on a computer monitor – over the air broadcast television for one thing. Else, you’ll *always* need a computer or a set of various players and receivers to use it, like we used to do – and then you have a bowl full of 50 remotes and if you want to watch TV you need to tune the TV to channel 3 and then the VCR to whatever channel you actually want but you have to use the stereo to change the volume and if you can’t hear it you need to check if it has the right input selected, but if you’re playing a tape then it needs to be on a different input and if you recorded the tape yourself I hope you remembered to adjust the audio source and volume because the VCR expects a different line level and it might blow out the audio or it might be too quiet…

          Getting back on topic, it’d be fairly convenient though non-critical if it wasn’t necessary to have a separate stereo cabinet just to play music. The capabilities of a basic modern car stereo would be just fine and a TV could easily support that without a full computer. (Specifically, I am thinking of support for FM, Bluetooth, and external storage, with the ability to see the titles of songs or the tuned frequency onscreen and control more than the volume with the TV remote.) I wouldn’t try building in a CD player or anything, but those few things wouldn’t be too bad.

          A more advanced version could stand to also be able to play video from the external storage, a capability it would share with the mp4 players we started to get before smartphones took over. Codecs could become an issue over time, but still. Maybe it could also support wireless screen streaming, even if it’d probably become outdated even sooner. Hopefully it would be made so that being unable to use one of the features doesn’t affect anything else.

          1. I imagine it does need some things, but not a full Linux computer. I know of at least one ATSC tuner chip that outputs the mpeg stream, so if you had that one then with another chip to decode the mpeg you could produce uncompressed video that you have to work into whatever you’re using. As an external device, I guess you’d need only one more step to translate that into hdmi or displayport for a display. I suppose the devices that actually sell probably stop at mpeg and expect you to give them USB and do the rest in software, but hey.

  4. I spent two decades making my living fixing those (and audio equipment). Been hit with high voltage from CRTs more times than I can remember. Actually, tjhat might be WHY I can’t remember all the times :lol: Once TVs became nothing more than SMT where swapping boards is more likely than tracking down and repairing at the component level and TVs became cheaper than dirt… I had to learn a new trade. I still remember those days fondly, though..

  5. Well, look at ebay – you like to buy PAL composite monitor? (the ones used in studios) – before the retro gaming craze they were junk, nobody wanted that anymore – now it is cheaper to get used LCD, with SDI even – because of retro gaming collectors with unlimited budgets. And analog TVs are going the same way – same reason.

  6. Attach the alligator clip of a jumper wire to the CRTs metal frame, attach the other clip to the shsfy of a long flat blade screwdriver (with an insulated handle), slide the tip of the screwdriver between the CRT and the rubber/silicone cup of the anode wire until you feel it contacting the anode or hear a loud voltage snap.
    Done, CRT discharged.

    Just make sure the jumper wire has end to end continuity.

      1. In the use case of discharging a classic all-in-one Macintosh, the spark is considered somewhat of a feature, giving the tinkerer confirmation that they have in fact discharged the device.

          1. I was once carrying a 21″ monitor downstairs in my office, with the screen against my stomach. At some point halfway down the stairs my hand slipped round to the IEC power socket. When my finger touched the middle earth connector, I got an almighty shock and almost dropped the thing (worth £1200 back in the day…)

            So I had picked up the charge off the screen by capacitance. An interesting lesson.

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