[HN Gopher] Replacing the bad flyback transformer in Apple's Stu... ___________________________________________________________________ Replacing the bad flyback transformer in Apple's Studio Display 17" Author : riveducha Score : 56 points Date : 2023-08-05 18:41 UTC (4 hours ago) (HTM) web link (www.riveducha.com) (TXT) w3m dump (www.riveducha.com) | aurizon wrote: | 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. | ivraatiems wrote: | 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! | Scoundreller wrote: | > 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 | nyanpasu64 wrote: | 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. | vondur wrote: | 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. | mhb wrote: | The capacitors are the things to be concerned about. | wkat4242 wrote: | 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 you're doing you probably wouldn't need this | guide in the first place :) | glhaynes wrote: | 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! | rasz wrote: | 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. | toast0 wrote: | 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. | wkat4242 wrote: | 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). | sneak wrote: | 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. | amelius wrote: | 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. | nickt wrote: | 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... | Dylan16807 wrote: | 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. | kens wrote: | 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 | tgsovlerkhgsel wrote: | 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. | formerly_proven wrote: | An electrician's voltage tester (the not-fake ones) can be | used for this, for off-line filter caps anyway. 30 kV, not so | much. | the_third_wave wrote: | 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. | dougg3 wrote: | 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. | | I think Apple should have recalled these. | riveducha wrote: | 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. | metadat wrote: | 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! | veave wrote: | I find your accent soothing. | andyjohnson0 wrote: | 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.) | ComputerGuru wrote: | 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. | fragmede wrote: | 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. | jrmg wrote: | 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? | JonathonW wrote: | 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. | xur17 wrote: | A rule of thumb I've always used is that 100W for a month | costs roughly $10. | toast0 wrote: | 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. | Hizonner wrote: | > 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. ___________________________________________________________________ (page generated 2023-08-05 23:00 UTC)