There have been some past rumblings on the internet about a capacitor being installed backwards in Apple’s Macintosh LC III. The LC III was a “pizza box” Mac model produced from early 1993 to early 1994, mainly targeted at the education market. It also manifested as various consumer Performa models: the 450, 460, 466, and 467. Clearly, Apple never initiated a huge recall of the LC III, so I think there is some skepticism in the community about this whole issue. Let’s look at the situation in more detail and understand the circuit. Did Apple actually make a mistake?
↫ Doug Brown
Even I had heard of these claims, and I’m not particularly interested in Apple retrocomputing, other than whatever comes by on Adrian Black or whatever. As such, it surprises me that there hasn’t been any definitive answer to this question – with the amount of interest in classic Macs you’d think this would simply be a settled issue and everyone would know about it. This vintage of Macs pretty much require recaps by now, so I assumed if Apple indeed soldered on a capacitor backwards, it’d just be something listed in the various recapping guides.
It took some very minor digging with the multimeter, but yes, one of the capacitors on this family of boards is soldered on the wrong way, with the positive terminal where the negative terminal should be. It seems the error does not lie with whomever soldered the capacitors on the boards – or whomever set the machine that did so – because the silkscreen is labeled incorrectly, too. The reason it doesn’t seem to be noticeable problem during the expected lifespan of the computer is because it was rated at 16V, but was only taking in -5V.
So, if you plan on recapping one of these classic Macs – you might as well fix the error.
This sort of thing happens way more than people realise, often the caps fail open circuit and all the end user sees is degraded performance or system instability. Sometimes they fail short and the device power supply goes into protection preventing start up or some other device on the board fails as a side effect.
cpcf,
I’ve seen capacitors explode twice….scary as heck…you instinctively rush to shut everything off. I’ve always assumed it was the defective parts lottery rather than an engineering mistake, but I guess the latter is possible.
IIRC one was an AOC monitor. They actually tried to deny warranty because when the monitor’s power supply failed, it apparently caused a lot more damage outside the power supply. They claimed they could not fix the monitor due to the extent of damage, and they would not replace the entire monitor under warranty.. I felt this was a load of crap to get out of honoring their warranty, but they were going to leave me hanging with no working monitor, I was really pissed about this so I insisted that they fix the monitor’s power supply and return it to me despite the fact that the rest of the monitor would still be broken. Even though it was a BS policy, I was still going to hold them to it. By their own documented admission the faulty part should be covered.
Well this must have left an impression on the supervisor because while they couldn’t fix the broken monitor, they relented and sent out a new one, haha. Do people in the EU have the same fear that warranties might be denied?
My EU experience.
Case 1:
Just two months ago, I purchased an ink cartridge for my Canon Pro-1000 printer and installed it. The printer keeps accusing me of having installed an empty cartridge.
Canon forwards me to reseller, reseller forwards me to Canon. I am still stuck in the loop. Meanwhile, of course, I purchased another cartridge, because I need my printer to work. Due to low cost, I will probably give up the fight.
Case 2:
My Lexmark laser printer, purchased with extended warranty (5 years). One year before the end of the period, it starts printing periodic black dots on the edges of the pages after a paper jamming incident. Lexmark claims its due to a “consumable part” (even though I operate at 10% of the maximum recommended cycle), and rejects repair. The case never got solved.
We’ve been printing for centuries, and printers still suck. I can totally see some random monk ringing Guthenberg and complaining his printer doesn’t work and getting forwarded to the confessionary.
Sad off-warranty cases:
– TV breaks one month after the end of the warranty. LG claims impossible to repair. For sure it was the logic board.
– LG Home Theatre system (blu-ray+amplifier+speakers) gets stuck in a “Please Wait” loop. LG claims they don’t manufacture the spare part (even though the system was 3 years old) and charged me 100 EUR for “ecologically disposing of the rest” + 25 EUR “diagnostics fee”.
Happy cases:
– Seagate hard drive fails SMART test after 18 months of 24/7 use (NAS drive): replaced on spot.
– Refrigerator compressor making noises, also ~18 months into use: technician came home and replaced it on spot.
– Apple MacBook Pro with swollen battery: laptop taken into service and returned after a week.
Happiest case:
– My Nikon F6 is still fully accepted for repairs. Put it in a box, shipping label provided by Nikon. Camera is returned in a month tops, straight from Japan.
Canon, Lexmark and LG, you were looking for trouble, weren’t you ?
I only have two LG devices, an OLED TV and LCD. After about a year the OLED developed burn in from a broadcaster logo which should not happen if the panel is working correctly, I contacted LG directly and they sent a technician to check it out, then replaced the whole TV without debate.
We have a few Canon printers and cameras, the main problem we’ve had with Canon seems to be caused by resellers or grey market vendors rather than Canon itself particularly on the printer side. On the camera side of things I’ve found Canon very good to deal with.
I can’t comment on the corporation ethics, but given the bulk of the debate on OS news surrounds, MS, Apple, Intel, AMD, Nvidia we can’t take the high ground.
@Alfman
I had an almost identical experience with a Samsung monitor, an exploding electrolytic filter cap on the PSU sub-board that basically melted the shielding and plastic case. Initially someone tried to claim it was a lightning strike, except there was no damage in lowly rated components leading to the failed component.
This was also the case on a couple of different Amiga models (the A4000 and CD32 both have this on certain revision motherboards). The result of these capacitors being connected backwards is a significantly reduced lifespan of the capacitors. However, failed capacitors don’t automatically mean a failed machine – often these capacitors are just there to reduce the switching noise in power rails that comes from having lots of logic gates in a small area. The more of these capacitors that fail, the more sensitive the chips to noise from the machine itself and other sources, and the more unstable it will be. The main risk from these capacitors failing is that some types spill their guts onto the PCB when they do, and start corroding it silently until eventually the machine *does* fail, not from the capacitor itself failing but from the secondary symptom of broken PCB traces.
Filters and buffers, nothing is perfect. We do not expect perfect, the main concern is when the manufacturer denies a component or device isn’t perfect.
Counterfeit components is another big issue.
Well it’s not new, I saw this when I recapped mine, and others did before me.
https://m.g3l.org/@mmu_man/108234642520249016
The only question remaining is, was the error done at the schematics (but we’d need the original to know), or was it “corrected” by the people doing the routing who thought it was wrongly wired and inverted it?
Now if only Bruce could fix his recap guide…