Ask Hackaday: Experiences With Capacitor Failure

Regular readers of Hackaday are intimately knowledgeable about old electronics, and whether it’s about that old oscilloscope sitting in the pile of other oscilloscopes, or the very rare vintage computer made in a Soviet bloc country, someone somewhere knows how to fix it. One of the biggest problems with these old electronics are capacitors. If it isn’t the battery that’s gone dead and leaked all over, it’s the caps that are either out of spec or have already exploded.

These machines can be brought back from the dead, and in recent months and years we’ve seen an uptick in the number of restomods hitting the Hackaday tip line. If you have a soldering iron and the patience to do so, any machine can be brought back from the grave.

Your Vintage Machine Is Probably Dead

Writing for ByteCellar, [Blake Patterson] asks an interesting question: what experience do vintage computer enthusiasts have with dried up capacitors?

Nearly every week, it seems, Hackaday gets another tip about a repaired or restomodded piece of hardware. There are always two problems. First, the battery leaked everywhere. That’s almost to be expected at this point, and if you’re very careful and very good, the damage caused by either AA cells or exotic lithium backup batteries can be repaired.

The second main issue faced by vintage computer enthusiasts is leaking caps. This is a subtler failure than a leaking battery. First off, not every capacitor will leak, or go bad. It might be out of spec and bring the whole system down with it, but that doesn’t mean it leaked all over the board. Second, not every capacitor will go bad. Ceramic disc capacitors are just fine, SMD caps can be ignored, and tantalum caps can be hit or miss. Larger electrolytics seem to be sturdier than smaller electrolytics, somehow, and everything is completely dependant on the model of computer and how it was stored. If you found a commodore in a barn with wild temperature swings over the seasons, you might be out of luck. If you’re pulling it from the back of a closet, you might be okay. Inexplicably, new old stock electronics — like the Nintendo Power System that’s still mint in box — are usually okay.

Fun With Capacitor Plague

But capacitor problems can crop up in equipment that isn’t as vintage as a classic Amiga or Tandy. In the mid to late-2000s, capacitor plague was the cause of many failures in consumer electronics. Capacitor plague was a result of defective electrolytic capacitors made between 1999 and 2007, with the first problems showing up sometime around 2002. The symptoms are easy to diagnose: if a device from this era doesn’t work, take a look at the power supply. If you have some goo around the caps, or the tops are cracked open, you’ve got capacitor plague. The implication of this is that consumer electronics, everything from LCD monitors to computers, were discarded in huge numbers. In fact, the coolest hackers we know took advantage of capacitor plague and collected LCD monitors, bought some threaded pipe from Home Depot, replaced the caps, and set up an awesome Matrix-style multi-monitor battle station.

A blown-up capacitor. Image source

The origins of capacitor plague come from water-based electrolytes developed in the late 90s. Water-based electrolytes are advertised as low-impedance, low-ESR, and high ripple current, all properties that are well suited for power supply design. These water-based caps unfortunately produced aluminum hydroxide when reacting with the cap ‘can’, and reacted to produce hydrogen. This hydrogen built up in the capacitor until the the stamped ‘vent’ on the top of the cap broke.

Although the origins of this type of failure date back to the late 1990s, it was only until the mid-2000s that capacitor plague really set in; these caps will pass initial testing, and it will take hundreds or thousands of hours for these caps to fail. Even in 2012, we were seeing tutorials on replacing bad caps in computer equipment, and for some this became a very fun and somewhat profitable way to equip a computer lab.

How Prevalent Are Bad Capacitors?

There is no community with more expertise in the repair and refurbishment of various bits of our electronic heritage. Here, you have people rebuilding old video game consoles into new portable consoles, turning literal trash into objects that belong in a museum, and repairing vital equipment that has been in use for the last few decades.

What is your experience with broken, dead, and abused capacitors? Did you have fun with a whole lot of monitors around 2006? What have you brought back from the dead, and what, if any, recommendations do you have for hardware designers of today?

Unfortunately, we’ll always have to use caps, and of course manufacturers will always use the cheapest caps available. Dead and dying capacitors will be with us in the future, and it’s up to us to maintain the equipment built decades ago and today.

(Banner image Lincoln Phipps, just one tale of woe among thousands.)

This entry was posted in Ask Hackaday, capacitor, capacitor plague, Hackaday Columns. Bookmark the permalink.

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