Sonnet Encore/ST G4: How a Tiny Capacitor Destroyed a Rare Upgrade | Retro Reverend<br>Skip to main content

July 11, 2026 Tantalum Fall Down, Go BOOM: How a Tiny Capacitor Destroyed One of the Rarest Upgrades in the Workshop<br>A component no larger than a fingernail killed one of my rarest Power Mac G4 processor upgrades. Can this Sonnet Encore/ST Duet 1.8 GHz card be saved, or has a piece of PowerPC history been lost forever?

The message from Jeron wasn’t the one I expected.<br>The Workshop Power Mac G4 MDD was in the shop for better cooling and a routine refresh before taking its place in the Workshop. Instead, I was staring at photographs of a processor card with scorch marks across it and a brief note: one of the tantalum capacitors had exploded.<br>Of all the components that could have failed, it had to be that one.<br>The component that went “boom!” was a Sonnet Encore/ST Duet dual 1.8 GHz upgrade, one of the most desirable aftermarket G4 processor cards produced. They rarely appear for sale today, and when they do, they're usually snapped up pretty fast.

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Mine hadn't just quit working. In a matter of seconds, it suffered catastrophic failure, leaving the card badly damaged and the upgrade seemingly lost.<br>Ironically, the work Jeron was performing had nothing to do with the processor itself. The goal was just to improve cooling around the card, giving it the best possible chance of surviving for years to come. But I guess fate had a different plan.<br>The damage wasn't confined to the capacitor itself. The explosion scorched nearby circuitry and made the entire upgrade unusable. Fortunately, the Power Mac's logic board survived the incident, but the processor card did not.<br>If there is any consolation, it's that the machine itself lives on. Jeron replaced the destroyed Sonnet upgrade with an official Apple dual 1.42 GHz processor module, the fastest factory processor Apple ever shipped in the MDD. The computer now runs beautifully. So from a practical standpoint, the Workshop still ended up with one of the most capable Power Mac G4 systems ever built.<br>But the collector in me is still mourning.<br>The Sonnet Encore/ST Duet 1.8 GHz was not a common upgrade. Produced in relatively small numbers during the twilight years of PowerPC Macs, these cards represented the pinnacle of aftermarket G4 performance. Finding one today is hard enough; losing one to an exploding capacitor is almost unbelievable.<br>What's particularly frustrating is that tantalum capacitors are generally considered among the more reliable components in vintage electronics. Unlike aluminum electrolytic capacitors, which commonly dry out and fail with age (or leak), tantalums have an excellent reputation for longevity. They do have one unfortunate characteristic, however. When they fail, they tend not to fail quietly.<br>Instead, they often fail dramatically.<br>A manufacturing defect, decades of electrical stress, microscopic internal damage, or even a tiny short circuit can cause a tantalum capacitor to enter thermal runaway. Rather than gradually losing capacity, it can rapidly overheat, ignite internally, and literally explode. Thankfully, this is uncommon enough that many technicians work their entire careers without witnessing it firsthand.<br>The encouraging news is that the CPUs themselves don't appear to have suffered any obvious physical damage. Most of the destruction seems confined to the power regulation circuitry surrounding the failed capacitor. Whether the board can actually be saved remains an open question.<br>Which brings me to this article.<br>If you're an experienced electronics technician with expertise repairing multilayer circuit boards, replacing damaged traces, or performing component-level restoration - and you're willing to tackle what may be a very challenging repair - I would genuinely love to hear from you.<br>This card deserves one more chance.<br>No promises. No guarantees. It may ultimately prove beyond saving. But if there's even a possibility that one of these increasingly rare Sonnet upgrades can return to service instead of becoming an expensive display piece, I'd like to try.<br>After all, preserving vintage Apple hardware sometimes means accepting that restoration isn't always about replacing parts. Sometimes it's about rescuing the parts everyone else has already given up on.<br>And sometimes it starts with a tiny capacitor that decided to remind everyone why electronics can still surprise us.

Post Details<br>Published July 11, 2026

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