I have a fully functional third-gen iMac (the "jelly bean") that needed its inner bezel replaced. Sourcing a non-broken bezel was one big job, but even after I did, finding someone with the knowledge and skill to repair it safely was a task. I wasn't willing to do the repair myself, it's just too dangerous for an amateur. These machines are supposed to have components that automatically discharge the screen after they're removed from wall power, but on a 20+ year old machine, no way to know whether that was working. You have to touch the screen and fasten it to the inner bezel, so repairing it without proper discharge was a non-starter.
I called around to various TV repair shops and was generally told they couldn't do it, or that it'd be prohibitively expensive. Finally, an electronics surplus store in my area referred me to a gentleman of the old-school AV hippy variety who knew how to repair all sorts of old equipment. He was able to construct a tool to ground the machine while working on it and we did the repair successfully together. It was an adventure!
Everyone in the comments keeps saying "if you don't know what you're doing, go find someone that does, skip the work, dont touch it", etc etc.
i'm here to say that that kind of behavior doesn't foster self improvement and learning.
here's what I suggest : learn about the job, learn about the hazards, take the precautions, get the equipment, don't let your guard down, and then do the work by-the-book.
you'll learn something in the process, both about the thing itself and the concept of maintaining a 'safety culture' around work that requires it. You won't get hurt, because you're going to follow the right safety precautions and work procedures.
Now, if you want to throw your hands up and just say "i'm not willing to put the hours in to ... " , then by all means, don't take the risk -- have it done. If you're in this for the pursuit of knowledge/skill/craft/gratifications then just pursue it as you would anything that is potentially dangerous and take the right steps.
You wouldn't tell someone to stay off a motorcycle, it's an enjoyable past-time -- you would remind them to follow safe driving procedure and to wear protective equipment.
I‘m generally with you here. I also like to learn and do stuff on my own. But there is a catch to some things when self thought. One can read and watch videos for hours and still miss a crucial detail that only a master in the field could teach you. I have high respect when it comes to high voltage, high/low temperatures or any machine work with fast spinning items. One should build up knowledge and confidence in a slow pace when no instructor is present.
For repairing your laptop sure, but there are huge risks with very low margins for error for safety in terms of dealing with high voltage electricity. If you want to do this safely you need to take the relevant electrical classes/certifications to know how, it’s not something a beginner can jump into without assistance. Sure if you fuck up a laptop repair it’s not a huge deal but this will fucking kill you if you’re not careful. Sure you can learn how to ride a motor cycle but you still need a license to do so and pass classes first, and most people deem the risks, efforts, and costs too high to be worth it.
As the author says CRTs are dangerous. Even when they're off they can still carry insanely high voltages. The flyback transformer is one of the more dangerous components of them.
I'm great at electronics repair and I tend to avoid them. Luckily these days that's easy :)
If you don't know what you're doing, you shouldn't attempt it. Just get a more technical friend to do it.
If you do know what you're doing you probably wouldn't need this guide in the first place :)
I've never worked inside a CRT (but may need to soon) and am not great at electronics repair, but I'm a little surprised you describe yourself as having a lot of skill but still tend to avoid them. From my understanding, it's straightforward to reliably discharge them and make them safe to work on. Do you think it's easier to get this wrong than I've understood or do you just feel uneasy about it in general? Just curious!
It's just the risk. Most components in a modern TV are very safe to work on. Even the PSU is not that bad. CCFL backlight had voltages only in the hundreds of volts, and modern LED backlight is even lower. A CRT is totally different business. The author of the article pointed out another thing, wire insulation properties at such high voltages.
There's just a lot to consider, and extremely high voltage stuff isn't really my area. I tend to do more low voltage stuff. When things go wrong with high voltage they tend to go wrong pretty spectacularly, and can cause serious bodily harm too. I just prefer not to take the risk. I'm similarly cautious with Li-ion and Li-Po battery charging circuitry. I don't like to mess around with those and if I repair them it's purely a like-for-like repair.
Another thing is that when I started with electronics CRTs were still very common and I wasn't skilled then, as such I had a lot of respect for them and a lot of caution. As my skills grew, CRTs became obsolete so I never really got comfortable with them and the apprehensive feeling remained.
But I think I have skills with electronics yes, I repair a lot of electronics, designed some of my own and I also built and modded some radios, and came up with some of my own mods (I have a ham license too).
Im an EE that never worked on CRT and declined plenty of requests. I also like to think Im quite mechanically inclined, but I would _never_ go anywhere close to a split rim being serviced. There are things just not worth the risk in life, like jumping head down into unknown stream, or skating down handrails.
Split rims is a good example of the kind of risks - they can be handled correctly but the temptation to skip steps is always there - but much more strongly there for people who do it a lot. If you replace them once, you can be anal about the safety (cage + chain + remote fill) because you don't need the speed.
I'd still replace the worst split rims with at least deuce rims.
One problem is there are a lot of adjustments that are really best made while the CRT is on. Another problem is CRT circuit boards experience a lot of heat, so repair work can be frustrating; it's hard to replace components and what not when traces have lifted.
Ah, electronics hobbyists these days... I repaired my first TV at 16yo, it was a Nordmende B&W set with a resistor directly on the output of the flyback transformer. That resistor was broken which led to a nice corona discharge lighting up the inside of the set, looking at it was like looking at the set of a 30's Frankenstein movie. This set me up for a 'career' of repairing televisions and (later) monitors while at university where I came across all sorts of interesting light/sound/smoke effects from those 35kV flyback transformers with cascade circuits (called 'tripplers' since they were used to raise the output voltage) on large-tube sets.
I never got zapped which is a good thing since yes, that can be unpleasant and - depending on when and where it happens - dangerous. Discharge those tubes and cascades before you fiddle with them, use a screwdriver connected to a ground wire which is connected to the metal tube frame. If you want to do it 'professionally' you'll want to put a HT resistor in that wire, otherwise just zap the thing by sticking the screwdriver under the plastic cap on the high tension connector at the tube.
It's not the transformer that's dangerous, it's the capacitor usually attached to it that's the problem. As transformers are passive components and do not store energy, they will not work without any power attached. The capacitor - if charged - will discharge through that transformer. NOW the transformer becomes dangerous, as usually the capacitor is at the low side for input, and your output voltage is multiplied a hell of a lot.
We do have the mantra in the styropyro discord "Do not the MOT" (Microwave Oven Transformer) but we all know it's harmless without power on it.
I've always wondered why modern multimeters don't have a "discharge" option.
I.e., you select the discharge mode, put the probes on a capacitor, and watch the voltage go down, while an internal current limiter makes sure that it happens at a safe rate.
Not big enough in what way? A normal probe should be able to handle the distancing and the small current fine. Maybe it would lack insulation but I wouldn't use the word "big" for level of insulation.
Typical probes are rated for 600 volts (CAT III), so you'd have insulation rated for 600 volts between your fingers and 30,000 volts, which is kind of hazardous.
When you combine a running transformer and weak insulation, and also there's no exposed metal where you intend for the current to go. So that probably comes off pretty differently.
But my use of the word "maybe" is more because of overall confusion about the word "big".
For lower voltages, some do ("low impedance measurement" or LoZ). Not specifically meant for discharging capacitors but should work for that too.
But this only works up to the voltage the multimeter is rated for (i.e. usually 300 or 600 V). If you wanted to make it safe to put 30 kV across the multimeter, it'd have to be designed with sufficient insulation etc. for that.
Yeah, this webpage really should have a big prominent warning label at the top.
The flyback transformer can fucking kill you, and anyone who needs this webpage or is interested in the instructions (ie someone not working professionally in electronics repair and aware of such hazards) is less likely to know that.
That 'snap' is the arc and the voltage = zero until it gets going again - repeat.
This is common on old monitors as dust builds up and often a fix can be done by a careful cleaning plus application of 'corona dope' along spark paths. Turn it on in a dark room and watch/listen for the spark. Dope that path and alternate paths and dry with hair dryer.
Test.
There are universal repair flybacks - select what seems to fit. Usually the existing controller will serve - computer monitors are far smaller than most TV's of that era. Hardest thing is finding new old stock. To save the nation new flybacks can be wound - complex but doable. Hardest problem is adapting the space and circuit. The flyback can be wired point to point with hookup wire. Only the HV wire needs to be HV wire. Then you can zip tie the flyback in whatever space and dress the HV with respect.
> The focus knobs should be tuned so that the screen image is sharp. I don’t really have a good set of steps for this, so just play around with them until the monitor is as sharp as can be.
This explains my methodology for a lot of things in life
I haven't tried focusing a CRT with two focus knobs (horizontal and vertical?), but from my general experience with focusing a CRT oscilloscope and tuning VGA signal sharpness on CRT and LCD, one good way to focus is to create three B&W images of vertical stripes, horizontal stripes, and a checkerboard. When showing the vertical stripe image, tune horizontal focus until as much of the screen as possible is in-focus. Then repeat with the horizontal stripe image and vertical focus, then double-check on a checkerboard and regular desktop usage.
I thought that the two focus knobs would be horizontal and vertical focus, but they weren’t. Not sure how they work but there are only four options to try out (increase or decrease knob 1 or 2) so didn’t take long to do.
Thanks for sharing! I had a brand new one of these displays in 1999 when they first came out and it developed the same problem a year later. The replacement from MacMall’s warranty company (which was graphite instead of blue) also eventually developed the issue too. Good to know there’s a solution if I ever decide to fix it.
The 21” version was supposed to be solid but I have never seen anyone with one or seen it for sale. The price tag was probably too steep compared to the faulty 17” one. Sad to hear that the graphite model was just as bad though.
Lots of detail and explanations. P.S. I'm not affiliated with anything, I just genuinely think this is one of the best (educational) channels out there on this.
This desoldering component technique video is well worth your time. Of all the basic electronics skills, doing this has always been challenging, particularly on older equipment where the copper traces will tend to peel up.
Having that happen is not the end of the world because a simple bodge wire is not hard to do in most cases.
But, there are times when a failure like that can really matter!
A flyback with the high voltages can be one of those times when you just want a clean replacement.
This guy shows you how to use wire to desolder many component pins at one time.
From what I understand of this, the danger comes from charge stored in large capacitors. So what is the longest that these capacitors can hold a significant charge if the crt is left disconnected from mains power? Hours/days/weeks? Is simply waiting long enough a reliable way to render a crt safe to work on?
(Irrespective of the answer to this, there is no chance at all that I would ever mess with crt circuitry. But I am curious.)
I used to bench repair on broadcast monitors. Typically, the flyback circuits have bleeder resistors and they discharge in several seconds. But you can never trust them. They can stay charged for weeks if the capacitor is good. An old capacitor damaged by heat will still hold a charge for hours. I always shorted them before replacing.
I remember building a crappy, but extremely dangerous (to the user), Gauss gun out of a stack of discarded disposable cameras, when I was much younger. I remember pulling out the capacitor and the charging circuit was pretty easy, and you just hook them all up in parallel, connect to a stack of AA or D cells in parallel. Still amazed I never died from doing crap like that. Definitely vaporized a few sections of skin and lit sections of my hair on fire a few times :)
I recall repurposing the Gauss gun as a tiny "handheld" EMP that would vaporize a section of wire. Made a Win95 thinkpad (ancient now, old then) do funny things.
I guess some clarification on the word "tase" is required. In my case, the shock threw me back some distance – I won't give in to hyperbole and say "threw me across the room" but 'twas nothing like the gentle tickle of 120VAC or the throb of 230VAC.
If the discharge circuit is not present/functional, it can be months[1], even if the capacitor was discharged at one point.
When working with high voltage/power equipment, its best practice to keep the capacitors shorted while you are working to keep dielectric absorption from “recharging” the capacitor to 1-15% of its rated voltage.
When working with high voltage/power equipment, its best practice to keep the capacitors shorted while you are working to keep dielectric absorption from “recharging” the capacitor to 1-15% of its rated voltage.
Wow, I was not aware. Nice tip. Does this also apply to TVs and computer monitors from the 1990s? Are they high enough voltage/power?
Maybe I was super lucky or somehow immune.. but as a Kid I got zapped by flyback transformers quite a bit of times.. (5 or 6 times?) It hurts,and it leaves a burn point where it touched.. but did not killed me.
Eventually I learned to ground the whole thing with a cooper cable and a resistor.
We had a bunch of these monitors back in the day, don’t remember any of them dying early. I was always afraid of taking apart CRTs thanks to those transformers in them. People used to overclock monitors back in the day to increase the refresh frequency.
I love this kind hardcore repair hacking to keep hardware going. There is no logical reason to spend time on this, yet someone did. Big respect to the author, you are inspiring!
> To fix a quarter-century-old monitor that was nothing special when it was new.
> Why? I mean, I wouldn't bother fixing the thing anyway, but hiring somebody is going to cost you more than a much better brand new monitor.
There are folks out there who spend their time fixing unexceptional cars such as old Ford Orions, Austin Metros, VW Golf Mk 3's (poverty spec) and so on. In their day these were the most boring of the mundane mass market motors you could buy.
But it's about capturing and snapshotting a point in time. Sure this particular monitor was probably crap, but combined with a same period Mac it's a time capsule.
You might think it's a waste of time, for others it's a hobby/past time. And it's one less thing in the landfill.
Collecting and repairing vintage computer electronics as a hobby is comparable to lego or embroidering, except for this one specific example where it will easily Fking kill you. People might not expect mellow past time to have such dangerous traps.
The sad reality of externality-removed capitalism is why would you do that? In our disposable economy, a new monitor can be had for cheap. Repairing things is for the poor or nerdy. which I resemble the latter pay. Incentivizing fixing things, rather than buying a new shiny flashy thing is not a thing that we do well. Oh well. Hopefully room temperature superconductors and solar and batteries can lead is to a place of victory for the environment in place of coal.
A new monitor can be had for cheap, yes. But a new CRT monitor cannot be had for cheap. If you have reason to prefer a CRT, repairing a monitor you have is probably the least cost option towards getting a working CRT.
Many people don't have reason to prefer a CRT, and that's fine too. Lots of non-CRT options out there to use.
Even with the externalities accounted for, if you must use a monitor, it might be better to buy a new one than repair the old one.
The replacement parts have a footprint, and a newer monitor might use so much less power in operation that it’s more efficient to make and use it than to continue to use the older CRT.
I really wish there were an easy way to work out if this was where the ‘efficiency crossover happens in X years of use’ point was. For example, I have a perfectly usable Thunderbolt 1 [edit: Thunderbolt 1 dock] that meets my needs. But it uses 5-10W of power more than a new Thunderbolt 3 or 4 one would. Should I continue to use it or switch to a newer one?
It'll depend on your usage pattern and local cost of electricity-- if you're running that device that uses 10W more power 24/7, that works out to 87.6 kWh of additional power usage over the course of a year, or about $15 at the current average cost of electricity in the US ($0.17/kWh as of June 2023). If that's a monitor, you'd have to run it for a pretty long time before your break-even point on purchase cost alone (10+ years on a lower-end monitor, and probably not in your lifetime on something from Apple).
If your usage isn't continuous (which it probably isn't), that'll reduce your electricity cost and extend your break-even point even further; if electricity costs more in your region, it'll shorten it (average EU energy prices are around double that of the US IIRC, and some countries are much higher). But it's still going to take a while to break even if the efficiency improvements you're considering are in the 5-10W ballpark; that's not all that much power in the grand scheme of things.
In MA, it works out that 1W continuous is about $2/yr, which makes for a quick way to inform “is this efficiency project worthwhile?” or “is this convenience load worth the convenience?”
CRTs have properties quite different from LCDs, so many gamers (or media consumers) have reasons to prefer them. Standard-definition TVs and PVMs having better compatibility with pre-HD consoles, and look better (subjectively and closer to developer intent). VGA CRTs can display multiple resolutions without scaling artifacts, and have a softer appearance than LCD monitors which enhances many games and artwork. And CRT flicker produces less motion blur than all non-strobed flat-panel displays at the same refresh rate (compare https://www.testufo.com/ on a LCD and CRT), and less latency than OLED or high-frame-rate/VRR displays (because liquid crystals take time to rotate into position).
Whether it's better to buy a new monitor or run a rescued CRT isn't merely a financial calculation based on manufacturing and operating costs and emissions. For retro gamers and CRT fans, LCDs are usually not a replacement for CRTs in gaming and media consumption, unless you use emulators and CRT shaders, or expensive scaler boxes which apply simulated CRT effects to real consoles' video outputs. And for all but the most obsessed CRT fans, CRTs are not a replacement for modern high-resolution LCD monitors for web browsing and office tasks (the sharpness, lack of flicker, and not having to juggle VGA DACs is a major advantage).
In practice the ideal display is a complex calculation based on scan rate (SDTVs can't show high-resolution signals and VGA monitors usually can't show television signals), display size (>40" LCDs are easier to get and move around than >30" CRTs), cost and reliability. Some people have multiple CRTs they maintain and use for different purposes (alongside LCDs), but I only have the space and energy for one VGA monitor (though I envy those with entire game rooms filled with vintage particle accelerator displays).
I called around to various TV repair shops and was generally told they couldn't do it, or that it'd be prohibitively expensive. Finally, an electronics surplus store in my area referred me to a gentleman of the old-school AV hippy variety who knew how to repair all sorts of old equipment. He was able to construct a tool to ground the machine while working on it and we did the repair successfully together. It was an adventure!