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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"

#51

Post by larusso »

serf wrote: post #37

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 som…

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.

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

#52

Post by extrapickles »

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…

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.

[1]: https://academic-accelerator.com/encyclopedia/dielectric-abs...

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

#53

Post by mjan22640 »

serf wrote: post #37

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 som…

The hazard here is that the very high voltage will kill you.

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

#54

Post by sokoloff »

xur17 wrote: post #28
JonathonW wrote: post #15

Earlier quoted context omitted.

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…

A rule of thumb I've always used is that 100W for a month costs roughly $10.

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?”

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

#55

Post by rasz »

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.

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.

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

#56

Post by throwaway2037 »

extrapickles wrote: post #52
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…

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. [1]: https://academic-accelerator.com/encyclopedia/dielectric-abs...

    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?

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

#57

Post by Grazester »

kens wrote: post #29
Dylan16807 wrote: post #22

Earlier quoted context omitted.

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. Here's a recent Twitter video showing what happens when you combine a flyback transformer and faulty insulation: https://twitter.com/zh1nu/status/1673487720780529664

Well that might have left a mark. Why would they try to touch it anyway? Even well insulated, I wouldn't try to touch something I didn't need to.

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

#58

Post by ComputerGuru »

qingcharles wrote: post #45
ComputerGuru wrote: post #31

Earlier quoted context omitted.

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.

When I was an asshole little kid I would pull these out of disposable cameras and use them to Tase people at school.

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.

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

#59

Post by clueless123 »

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.

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

#60

Post by ddingus »

https://youtu.be/Vou2xlJkuoU

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.

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