Last year I got my first Amiga CD32, which was very kindly given to me by a friend – these suffer from bad electrolytic capacitors on the mainboard and need to be properly serviced.
The console is pretty easy to take apart for inspection.
With the upper case removed, it was clear that the SMD electrolytic capacitors had indeed began to leak, in particular the 47uF 16V parts; the two through-hole 1000uF 10V audio capacitors had been replaced at some point in the past, which is necessary because these were installed backwards on the CD32 from the factory due to a silkscreen error marking them as the opposite polarity.
Aluminium electrolytic capacitors are commonly used for filtering, smoothing, and decoupling in both high- and low-voltage electronics. They are quite cheap in comparison to their solid-electrolyte counterparts (such as tantalum and polymer electrolytics), so are very common in consumer electronics.
Their useful lifetime is highly dependent on the specific application that they are used in (i.e. frequency, ripple current, steady-state voltage versus rating) and temperature, as well as the manufacturer and series of the specific component. They typically comprise aluminium windings which are coated with a liquid electrolyte, which can dry out over time (negatively affecting the performance of the capacitor, often causing them to fail dead-short), or even leak out and cause corrosion to the PCB and surrounding components.
SMD aluminium electrolytic capacitors are common, well-documented failure points in other pieces of equipment from the 1990s (i.e. Amiga 600 / 1200 / CD32, Apple PowerBooks, Apple Macintosh Classic / Classic II / SE / SE/30, etc), where they physically leak and cause board corrosion.
There is only one known production variant of the CD32 mainboard with the following electrolytic capacitor values and locations. The CD32 mainboard is fairly easy to recap as it only has three through-hole parts but quite a large number of SMD parts.
You can usually buy capacitor packs for these machines from sellers such as Console5, but I just made up my own by noting the specifications of all of the electrolytic capacitors on the board, and ordering a set of high-quality known-brand parts.
I decided to use tantalum electrolytic capacitors for the SMD capacitors and polymer aluminium electrolytic capacitors for the through-hole capacitors, both of which are equivalents to standard aluminium electrolytic capacitors – these use a solid electrolyte, meaning that they will not physically leak. I only ever use high-quality replacement parts, if you’re going to the effort to recap something then you should do it properly!
When substituting electrolytic capacitors, the capacitance needs to be the same, and the voltage rating can be the same or higher (within reason) – when you’re going through all this effort to recap something, be sure to use high-quality replacements.
For SMD capacitors, I usually remove all of them at once using a hot air rework station with kapton tape and aluminium foil to protect the surrounding areas, or by carefully twisting them off using needle-nose pliers (this technique may not be suitable if the pads are damaged, as they could delaminate from the board – and push downwards, don’t pull upwards!). The pads can then be cleaned up using new solder and either desoldering braid or a desoldering station. The board should then be thoroughly cleaned to remove any leaked electrolyte and leftover flux, using isopropyl alcohol and an ESD-safe brush.
As for through-hole capacitors, I usually remove each one-by-one using my desoldering station, then immediately install its replacement part – this minimises the likelihood of getting it wrong. The board should then be thoroughly cleaned to remove any leaked electrolyte and leftover flux, using isopropyl alcohol and an ESD-safe brush.
When fitting new electrolytic capacitors, you must take care to ensure that the value, voltage rating, and orientation of the new capacitor are correct – electrolytic capacitors are polarised, so must be installed the correct way around, else they’ll get hot when powered on (and probably explode). The polarity is marked on the case: for aluminium electrolytic capacitors, the negative side is usually shown by a white stripe (for through-hole) or a black bar (for SMD); for tantalum capacitors, the positive side is usually shown by an orange or white bar (for SMD). This catches a lot of people out!
You can’t always trust the orientation markings on the PCB silkscreen (if it even has them, not all boards do), as sometimes mistakes were made in the design from the factory (take the PCB layout of the audio circuit on the Commodore CD32, for example), so care must be taken to match the orientation of the new capacitor with the original. Make sure to take lots of “before” pictures for reference, and double-check throughout.
With this work done, the console powered up and loaded discs correctly.
I wanted to add a bit of extra usability to my CD32 in the form of a TF330 accelerator card, which features a Motorola 68030 CPU @50MHz, 64MB RAM, 2.5″ IDE connector for a CF card, RGB socket, and two USB HID ports – this also came with a 32GB SDcard with AmigaOS 3.5 pre-installed. I also added a 3D-printed cover.
Reassembling the CD32 is just the opposite of its disassembly.
With everything back together, the system works perfectly.
