Burned capacitor on my Cube Sonnet Processor board

[Wouter3]

When I switched on my Cube I heard a puff and smoke coming from the case. I could easily locate the problem as the smell of burned electronics directed me. Capacitor C102 on the Sonnet Encore ST G4 daughterboard has burned out, while the adjacent capacitor C95 is somewhat blackened.
Would anyone of you have schematic of this board with the specs of this component so I can replace the it. It might be worth saving my 1GHz CPU board.

 

[hardon]

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[Wouter3]

This is indeed a very similar board. Only a bit faster. I await responses, also from Sonnet, to see if my board can be repaired. If it is only the capacitor that needs to be replaced, it would be a lot cheaper then buying another board.

 

[Wouter3]

Just got this reply from the Sonnet Support Team:
"Those capacitors are 220uF,10V, 20%, case E Tantalum polarized capacitors. We don’t see the + sign on the silkscreen, but it the right side of the parts as shown. You can tell because it has a little nib on the + (anode) side.

These look like Sprague/Vishay conformal caps; I would recommend looking for AVX Tantalum caps as replacements; a bit more expensive, but better parts. You can find lots of caps at Digi-Key or Mouser".

Very helpful. I will first try to repair the capacitor(s), before to embark on buying another one.

 

[AphoticD]

Wow. Kudos to Sonnet for their comprehensive response.

Try getting an answer like that out of any big manufacturer... Typically the answer would be: “Your product is obsolete and no longer supported. Too bad.”

 

[1042686]

Agreed. Talk about service way after the fact. Kudos to Sonnet.

On a side note, does anyone have a video that shows the process for replacing a cap of that style?

 

[Wouter3]

There are many types of soldering advice on Youtube. E.g.

They emphasize on the use of flux

 

[1042686]

Awesome thankyou. I’ve done a lot of soldering repair work but focused on analog tube/valve amplifiers, cabs & guitar/bass harnesses.

Alas, These audio dinosaurs are not circuit boards which is very much a different animal in method & approach so the video assist is helpful.

Thanks again - didn’t mean to hijack your thread. Best of luck on your repair!

 

[weckart]

Wow. Kudos to Sonnet for their comprehensive response.

Try getting an answer like that out of any big manufacturer... Typically the answer would be: “Your product is obsolete and no longer supported. Too bad.”

I got exactly that response from Sonnet. More to the point, they no longer had any legacy Macs to troubleshoot with.

 

[Wouter3]

Finally the capacitor, according to Sonnet specs, arrived. I have soldered it in and the processor board works again. I would like to say that this burned capacitor was most probably caused by my malfunctioning Apple cinema display and not by the quality of the Sonnet components. The display has given problems in other areas and is replaced. The Cube is running stable again

 

[DearthnVader]

Finally the capacitor, according to Sonnet specs, arrived. I have soldered it in and the processor board works again. I would like to say that this burned capacitor was most probably caused by my malfunctioning Apple cinema display and not by the quality of the Sonnet components. The display has given problems in other areas and is replaced. The Cube is running stable again

Good work!

I'd have wrote it off as a lose and tried to find a replacement CPU. My surface mount soldering skills being what they are.

JOY!peffPWPC

 

[Wouter3]

I was lucky it this capacitor was the only component that so obvious blew up and nothing else. Otherwise finding the culprit would have been very difficult.

 

[rake_mistry]

Wow! Sorry to resurrect such an old thread, but I had the exact same thing happen to me back in 2017 with a Sonnet Encore ST G4 SG4R-1250 1.25GHz CPU upgrade in my G4 Cube! It was working fine, then one day BOOM puff of black smoke. I opened up the Cube, followed the smell, and was absolutely heartbroken to see the blown cap on the very expensive CPU card.

At the time my knowledge of electronics was very limited, so any repair seemed out of question, but I held onto the CPU just in case... Fast-forward to today and after getting into micro soldering and electronics repair during the pandemic, I found myself thinking about that CPU with the blown capacitor again.

I dug it out, removed the non-blown capacitor above it and used my Transistor Tester to identify it. Was getting around 210uF, so I figured it was likely 220uF but wasn't sure about the voltage until I noticed the capacitor just above it in parallel was a regular tantalum cap (instead of an unmarked conformal coated one like the one that blew up) with the markings "227A", which I just learned (from an AVX datasheet) means 220uF 10V.

Was just about to place an order for the replacement caps when I decided to search for "Sonnet Encore capacitor replacement" and to my surprise I found this thread. Thank you so much @Wouter3 for sharing this! The confirmation you received from Sonnet, and hearing that replacing the cap worked for you, has given me hope for this CPU card! This G4 Cube and CPU card were pivotal in my interest in vintage Macs and electronics repair, so if this works again it will be awesome.

Attached is a picture of my card (after cleaning; I have pictures from immediately after the puff of smoke but they're on an old hard drive) – you can still see the burn mark/melted plastic on the top-left corner of the connector. How shocking is it that it's the exact same capacitor (in terms of location on the board) that blew! I wonder if this is going to be a more common issue going forward 🤔 Obviously my card is a little different, with the positive side being the left side (as denoted by the line on the tantalum cap and the pointy end of the conformal cap), but the similarity in failure is still surprising.

Anyway, I'm leaving all of this information here in case it helps anyone else down the line. Will follow up once I get the replacement caps and test the card out again!

 

[rake_mistry]

Later follow-up on this than I'd have hoped, but I can confirm that ✅ YES, replacing the burnt capacitor fixed my old G4 Cube CPU upgrade card!

One odd quirk – despite having installed the Sonnet firmware update, the "About This Mac" window reports 1.2 GHz instead of the 1.25 GHz that it used to. "System Profiler" correctly reports it as 1.25 GHz, it's just the "About This Mac" window incorrectly showing 1.2 GHz. Not sure what's up with that, but I'm just happy to have the CPU upgrade working again in any capacity

I also dug up some old photos from before the cap burnt, after the cap burnt, and after replacing the caps to share with you all. Thanks again for making this thread, @Wouter3 !

Edit: unfortunately the pictures are out of order, but they're named/labeled with the chronological order