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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"

#11

Post by toast0 »

glhaynes wrote: post #7
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…

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 cur…

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.

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

#12

Post by the_third_wave »

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…

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.

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

#13

Post by wkat4242 »

glhaynes wrote: post #7
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…

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 cur…

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).

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

#14

Post by aurizon »

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.

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

#15

Post by JonathonW »

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…

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.

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

#16

Post by rasz »

glhaynes wrote: post #7
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…

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 cur…

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.

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

#17

Post by amelius »

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…

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.

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

#18

Post by nickt »

amelius wrote: post #17
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…

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.

The probes aren’t big enough. That’s why it’s often a big screwdriver and jump lead to earth.

The better option is the Fluke 80K 40.

https://www.fluke.com/en-us/product/accessories/probes/fluke...

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

#19

Post by sneak »

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…

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.

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

#20

Post by vondur »

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.
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