The capacitor that Apple soldered incorrectly at the factory

Definitely starting Wednesday off productively.

I found one a few years back when I repaired a linear power supply. This required me to reverse engineer it first because there was no service manual. I buzzed the whole thing out and found out that one of the electrolytic capacitors had both legs connected to ground. They must have shipped thousands of power supplies with that error in it and no one even noticed.

Also mentioned here: https://amiga.resource.cx/exp/a3640

The layout CAD is often done by a different team that follows the schematic provided by design engineering. Automated workflows are common. The silk screen is predefined in a QA'd library. It is not their job to double check engineering's schematic.

The components are placed per the layout data.

Both those teams did their jobs correctly, to incorrect specifications. In fact, the factory performing assembly often is denied access to the schematic as it is sensitive IP.

If you're going to cast blame on a 30 year old computer, at least direct it at the correct group. It wasn't soldered incorrectly at the factory. They soldered it exactly how they were told to - backwards.

P.S. still my favorite Mac of all time was the IIcx. That one coupled with the 'full page display' was a dream.

About 30 years ago I designed my first PCB with frequencies in the GHz range. It was full of challenging transmission line paths with frequencies in the hundreds of MHz and above.

I am still proud of the fact that all of the high speed signals worked as designed, with excellent signal and power integrity (the large FPGA was challenging). Emissions passed as well.

I did, however, screw up one thing: DC

I somehow managed to layout the DC input connector backwards!

These boards were very expensive ($2K), so an immediate respin was not possible.

I had to design a set of contacts to be able to flip the connector upside-down and make the electrons go in the right way.

The joke from that point forward was that I was great at multi-GHz designs but should not be trusted with DC circuits.

https://wiki.console5.com/wiki/Amiga_CD32 C408 C811 "original may be installed backwards! Verify orientation against cap map"

A4000 https://wordpress.hertell.nu/?p=1438 C443 C433 "notice that the 2 capacitors that originally on A4000 have the wrong polarity"

Much worse is Commodore A3640 68040 CPU board aimed at top of the line A3000 and A4000 http://amiga.serveftp.net/A3640_capacitor.html https://forum.amiga.org/index.php?topic=73570.0 C105 C106 C107 silkscreen wrong, early revisions build according to bad silkscreen.

until you have to deal with negative voltage (-5V). Another out of bounds bug.

I think the -5 volts is only there in case an expansion card needs it.

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

But it just never quite worked right. I remember how frustrated and confused my older brother was. The computers would sometimes see each other but would drop off so easily.

Was this that?!

I found a bad solder joint that looked ok, but was intermittent, and had been that way, in a Television built in 1948 and used for decades.

Bad design and assembly goes back forever, as near as I can tell.

This is the buried lede! I am of the opinion that half of the capacitors in any modern circuit are useless; the trouble is we don't know which half.

I wonder if it has the same defect