Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The capacitor that Apple soldered incorrectly at the factory

downtowndougbrown.com

Post reply on HN
Print view View original

121–130 of 269 posts

Re: The capacitor that Apple soldered incorrectly at the factory

#121

Post by rwmj »

mhardcastle wrote: post #108

Why include that capacitor at all if it doesn't matter whether it works?

If you look at the traces you can see the capacitor is right next to the power connector, on the -5V rail (which is not used for much, only for the RS422 serial port). The capacitor will be there to smooth the power supply when the machine is just switched on, or there's a sudden load which causes the voltage to "dip" above -5V. Basically it's like a tiny rechargable battery which sits fully charged most of the time, but can supplement the power on demand.

So you can see why it probably didn't matter that this capacitor didn't work: It's only needed for rare occasions. RS-422 is a differential form of RS-232 (https://en.wikipedia.org/wiki/RS-422) so being differential it's fairly robust against changes in load if they affect both wires. And the worst that can happen is you lose a few characters from your external modem.

In addition, electrolytics can probably work when reversed like this, at least a little bit. It's not exactly optimal and they might catch fire(!).

Re: The capacitor that Apple soldered incorrectly at the factory

#123

Post by toast0 »

nuancebydefault wrote: post #95
rvense wrote: post #39

Earlier quoted context omitted.

But when it does, it will probably be the capacitors in the power supply that have dried out.

How can I even know which capacitor is faulty?

If your model was popular, there's likely a recap kit for its power supply. It usually makes senss to swap all the capacitors in the kit, unless the kit instructions say otherwise.

You can look for physical signs of degredation (bulgy, leaky, discolored), but to really test a capacitor for capacititance, you need to take it out of the circuit, at which point, you may as well put a new, high quality capacitor in.

The OEM capacitors may likely have a just right voltage rating, a new one with a higher voltage rating (and same capacitance, compatible type) may last longer in cirucit as well.

Re: The capacitor that Apple soldered incorrectly at the factory

#124

Post by mmmlinux »

yborg wrote: post #122

I have a Quadra 700 of this vintage that hasn't been powered up in 25+ years. Kind of wanted to fire it up again to experience the glory of A/UX one more time, but sounds like I'd have to replace all the lytics :/

Do it sooner than later, the cap juice loves to eat PCB traces. same with the clock batteries, get those things out of there.

Re: The capacitor that Apple soldered incorrectly at the factory

#125

Post by magic_smoke_ee »

Workaccount2 wrote: post #109
kevindamm wrote: post #99

Earlier quoted context omitted.

Or much shorter, around two years, if it was part of the Capacitor Plague. https://en.wikipedia.org/wiki/Capacitor_plague#Premature_fai... The normal lifespan of a non-solid electrolytic capacitor of consumer quality, typically rated at 2000 h/85 °C and operating at 40 °C, is roughly 6 years. It can be more than 10 years for a 1000 h/105 °C capacitor operating at 40 °C. Electrolytic capacitors that operate at a lower…

This is also why so many LED bulbs are shit, lots of heat in a small space full of electrolytic caps.

Intentional planned consumption/obsolescence by design. This class of problem is where under-regulation and lack of standards benefits only sellers and cheats buyers. PS: Also, Amazon should be required to test all of the electronic, safety, and food products on its site such that they can prove safety and standards conformance.

Re: The capacitor that Apple soldered incorrectly at the factory

#126

Post by toast0 »

xxs wrote: post #75
Peanuts99 wrote: post #63

Earlier quoted context omitted.

A TV used to cost a few weeks pay and now you can get a TV for the equivalent of a few hours pay. There just isn't much of a market for a $3000+ TV.

Few usually means 3-5 or so, a half decent TV would be at least half a grand. That's rather high hourly pay rate.

Explain to me why this tv for $100 [1] isn't perfectly suitable to replace a 2008 40" 1080p Samsung LCD with florescent backlight that 2was a deal at $1000. Yeah, you could get something bigger and better. Yes, price comparison on a sale week is a bit unfair.

[1] https://www.bestbuy.com/site/tcl-40-class-s3-s-class-1080p-f...

Re: The capacitor that Apple soldered incorrectly at the factory

#128

Post by Filligree »

magic_smoke_ee wrote: post #125
Workaccount2 wrote: post #109

Earlier quoted context omitted.

This is also why so many LED bulbs are shit, lots of heat in a small space full of electrolytic caps.

Intentional planned consumption/obsolescence by design. This class of problem is where under-regulation and lack of standards benefits only sellers and cheats buyers. PS: Also, Amazon should be required to test all of the electronic, safety, and food products on its site such that they can prove safety and standards conformance.

That, and customers insisting on preexisting form factors. Fitting the electronics and LEDs into the space of a traditional lightbulb comes with compromises, such as not having proper heat dissipation on either.

Re: The capacitor that Apple soldered incorrectly at the factory

#129

Post by Workaccount2 »

magic_smoke_ee wrote: post #125
Workaccount2 wrote: post #109

Earlier quoted context omitted.

This is also why so many LED bulbs are shit, lots of heat in a small space full of electrolytic caps.

Intentional planned consumption/obsolescence by design. This class of problem is where under-regulation and lack of standards benefits only sellers and cheats buyers. PS: Also, Amazon should be required to test all of the electronic, safety, and food products on its site such that they can prove safety and standards conformance.

I am assuming you are an ee (like myself)...I have never designed a product with a built in expiration, nor have I ever seen any app notes or write ups on the engineering of it - something engineers love to do.

What I have seen done is cheaping out on parts in order to get the price as low as possible, because customers shop primarily on price.

Not to lash out, but it kind of hits a nerve for me, because people think we design products to purposely fail. Hell no, we try really hard to do the opposite, but everyone just loves to buy the cheapest shit.

The $25 LED bulb that will last for eternity will rot on the shelf next to the $3 bulb that will probably be dead in 6 months. And one more "they build these things to fail" complaint will be posted online.

Re: The capacitor that Apple soldered incorrectly at the factory

#130

Post by chefandy »

What’s the liquid in the old capacitors? PCBs? (as in polychlorinated biphenyls… that abbreviation collision always annoyed me.)

I think I know exactly enough about electronics to ask more annoying questions than someone who doesn’t know anything at all.

Post reply on HN