Macintosh IIci

Preventative Maintenance

Batteries

Like many other Macs from this era, lithium clock batteries installed in this computer may be susceptible to leakage at the end of their lifespan. These batteries typically have a date code, so you can check their age. If they are more than a few years old, they should be replaced. Some brands are more susceptible to leakage than others - you are unlikely to encounter a Maxell battery that is still intact, but a Tadiran battery that came with the machine may still be fine.

If the battery does leak, this results in a brown residue and extreme corrosion on any nearby metal parts, including motherboard traces. Motherboards with battery damage are sometimes repairable, but it takes many hours or days of labor and almost always requires replacement of proprietary parts - on this board, usually the ROMs and the RTC - as well as repairing many traces.

Some machines with battery leakage have been known to avoid motherboard damage if the board was kept in storage sideways, usually resulting in a damaged disk drive instead. The screws will be rusted in place, so will need to be drilled out to remove the drive from its plastic carrier sled.

Capacitor Replacement

The surface mount aluminum-electrolytic capacitors on this machine are susceptible to leakage after many years. A majority of problems encountered on this machine will be caused by this capacitor leakage, which causes corrosion of traces and pads nearby. To prevent this, these can be replaced by a newly-made version of the same aluminum electrolytic capacitor, but these may have the same leakage issue in a few decades' time.

A common alternative is to instead replace them with tantalum capacitors, which will never have leakage issues. If you do this, it is vitally important that your replacement capacitors have a higher voltage rating than the original. If you do not, you will be risking a much more violent type of capacitor failure that may short traces and leave a burning hole in the board.

Apple motherboards from this era typically have a capacitor de-rating of about 75%, meaning that a capacitor on a 12v line will be rated at 16v, giving a bit of a buffer between the expected operational level and the capacitor's max rating. Tantalum capacitors are much more sensitive to their max rating and so should be de-rated much more - at least 50%, so 24v rating for a 12v line.

This board also has axial capacitors. These are not known to have leakage issues, and replacing them is currently not believed to be necessary, but also is not likely to cause harm.

Original SMT Capacitor	Qty	Example Aluminum Replacement	Example Tantalum Replacement
10uF 16V	2	10uF 16V 4mm, EEE-FN1C100R	10uF 25V T491, T491C106K025AT
47uF 16V	8	47uF 16V 6.3mm, EEE-FP1C470AV	47uF 25V T491, T491D476K025AT

Original Axial Capacitor	Qty	Example Replacement
220uF 16V 8x18mm	1	220uF 16V 8x18mm MAL213835221E3
470uF 16V 10x18mm	3	470uF 16V 8x18mm MAL202135471E3

Known Problems And Solutions

Problem	Solution
Does not power on. Power supply +5v standby is present. Powers on from rear power button. No chime until keyboard power button is pressed. Powers on from either power button. Keyboard power button causes system reset. Powers on, but only intermittently. Sometimes powers off seemingly at random.	Startup circuit is damaged. Replace capacitors C6, C11, C12, and C13, if they haven't been. Clean the area around these capacitors of any corrosion caused by capacitor leakage. Check the traces surrounding these capacitors for corrosion and continuity, especially the traces leading to and from D3, D4, D6, and Q4. Clean corrosion and check continuity on the pads of UB13, UD13, UE13.
Powers on, but no chime. Chimes and boots normally if a compatible ROM SIMM (from IIfx or IIsi) is installed, and Jumper W1 is removed.	Check for damaged traces coming from the ROM DIPS (UM8, UM10, UM11, UM12). Damage looks like darkened spots along the trace - if found, check continuity on either side. Possible hidden corrosion under battery socket BT1. Desolder and remove socket, and check traces underneath for corrosion and continuity.
No chime or other sound from built-in speaker. Boots normally, sound from audio jack works No sound at all, but otherwise boots and operates normally	Possible damage from capacitor leakage near audio circuits. Replace capacitors C2, C3, C5, and C9, near the audio jack, if they haven't been. Check nearby traces for corrosion and continuity. Check pads of UB2 and UB3 for corrosion.
Non-working modem/printer ports	As with missing sound, likely damage from capacitor leakage near audio circuits. Replace capacitors C2, C3, C5, and c9, near the audio jack. Check nearby traces for corrosion and continuity. check the pads of J4, J5, UA4, UA5, UC4, and UC5 for corrosion. Rarely caused by a faulty SCC chip (UC6).
Internal floppy drive does not read disks, but eject works Internal floppy drive reads disks, but cannot eject properly Replacing internal floppy drive has same symptoms External floppy drive works	Likely caused by damage from capacitor leakage in the startup circuit, and preceded by or accompanied with those symptoms. Replace startup circuit capacitors if not done already. Check traces for corrosion and continuity on underside of board around the startup circuit, particularly around the small slot in the board near R43, and the cluster of traces running along the side of the board next to that slot.
Neither external nor internal floppy drive works properly	Check for corrosion on pads of the SWIM chip (UA11), and for corrosion and continuity on surrounding traces. If none found, may be caused by a faulty SWIM. This is a custom part, not readily available - it will need to be harvested from a dead board.
Drives connected to the internal SCSI bus are not detected or otherwise do not work properly Drives connected to external SCSI show no issues	Likely caused by damage from capacitor leakage in the startup circuit, and preceded by or accompanied with those symptoms. Replace startup circuit capacitors if not done already. Check traces for corrosion and continuity on underside of board around the startup circuit, particularly around the small slot in the board near R43, and the cluster of traces running along the side of the board next to that slot.
Drives connected to both internal and external SCSI bus are not detected or otherwise do not work properly	Check for corrosion on the pads of the SCSI controller (UA10). If none found, may be a faulty chip. Despite being a legacy part, replacements are readily available and easy to obtain. Compatible 53C80 controllers are/were manufactured by NCR, AMD, and Zilog, and as of 2021 are still available for purchase new from electronic component distributors.