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Replacing the bad flyback transformer in Apple's Studio Display 17"

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Re: Replacing the bad flyback transformer in Apple's Studio Display 17"

#31

Post by ComputerGuru »

andyjohnson0 wrote: post #30

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 got a really nasty shock from a capacitor in a flash (as in camera) that was powered down for weeks, back in the 90s.

Re: Replacing the bad flyback transformer in Apple's Studio Display 17"

#32

Post by nyanpasu64 »

Scoundreller wrote: post #2

> 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.

Re: Replacing the bad flyback transformer in Apple's Studio Display 17"

#34

Post by nyanpasu64 »

jrmg wrote: post #8
fragmede wrote: post #6

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…

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…

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).

Re: Replacing the bad flyback transformer in Apple's Studio Display 17"

#35

Post by teh_klev »

Hizonner wrote: post #26

> Opening up CRTs is dangerous. Do this at your own risk. Considering hiring a professional instead. Hire a professional. 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.

> 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.

Re: Replacing the bad flyback transformer in Apple's Studio Display 17"

#36

Post by riveducha »

nyanpasu64 wrote: post #32
Scoundreller wrote: post #2

> 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.…

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.

Re: Replacing the bad flyback transformer in Apple's Studio Display 17"

#37

Post by serf »

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.

Re: Replacing the bad flyback transformer in Apple's Studio Display 17"

#38

Post by lightedman »

wkat4242 wrote: post #3

Nice job and write-up. 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…

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.

Re: Replacing the bad flyback transformer in Apple's Studio Display 17"

#39

Post by kmbfjr »

andyjohnson0 wrote: post #30

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 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.

Re: Replacing the bad flyback transformer in Apple's Studio Display 17"

#40

Post by mvandermeulen »

ivraatiems wrote: post #27

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 the…

> we did the repair successfully together

Excellent anecdote and love to hear that these people still exist

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