Last year, I repaired an Apple PowerBook 1400CS-166 for a friend of mine, which required a recap of the mainboard, backlight board and display driver board, a replacement for the leaky original NiMH battery pack, a mainboard repair, and a new power supply.
Originally, the system seemed completely dead with no response to the power button.
Disassembly
Disassembly of the PowerBook 1400 is a fairly complex process, but it’s easy enough to do following this excellent comprehensive guide.
Mainboard Recap
The SMD aluminium electrolytic capacitors on the 1400 mainboard are a common problem – they physically leak which causes corrosion, and they don’t perform as intended which can cause all kinds of weird issues including a completely dead unit. I therefore decided to replace them – see my general advice for electrolytic capacitor replacement for more detailed information on the process.
The 1400 mainboard is easy enough to recap, having only ten SMD capacitors:
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.
In this build, I decided to use tantalum capacitors for the smaller capacitors in the display boards and polymer capacitors for the larger capacitors on the mainboard – these use a solid electrolyte, meaning that they will not physically leak.
Display Boards Recap
There are two boards in the display area which also suffer from leaky SMD aluminium electrolytic capacitors, including the backlight and display board.
The backlight board can be accessed by removing the RF shielding around it – on this unit it has only two electrolytic capacitors which I replaced with the following:
The display board can be accessed by removing the display bezel.
The display board has six electrolytic capacitors, which I replaced with the following:
- 4 x 3.3uF 50V tantalum SMD electrolytic capacitor.
- 1 x 10uF 16V tantalum SMD electrolytic capacitor.
- 1 x 33uF 10V tantalum SMD electrolytic capacitor.
PRAM Battery Rebuild
The 1400 has up to two internal PRAM battery packs, each of which is made up of two individual rechargeable cells. After a long time in storage, these were understandably dead, and due to their age I decided to replace them anyway.
I bought four replacement Panasonic VL2330 cells with pre-attached solder tabs, and soldered them together with the original flying leads – two in series with a balancing lead in the centre. I then wrapped the new packs in some electrical tape to help insulate them, and fitted them back into their original shells.
Battery Pack Rebuild
The original laptop battery pack was completely dead – I dismantled it to check the condition of the NiMH batteries inside, and unsurprisingly these were leaking.
The original is a 9.6V 4000mAh NiMH pack, comprising a Sanyo 8HR-4/3FAU (13.5cm x 7cm x 2cm) – I found a replacement pack for sale that may be suitable, however the owner decided not to go ahead with the replacement, so I gutted the original pack instead.
Mainboard Repair
With all this work performed, I tested the machine out with its original M4896 PSU, but it was still completely dead – I tested the PSU and its output voltage was insufficient, I dismantled it to inspect inside and the output side seemed to be burnt up (probably due to overload, more on this later).
I salvaged the proprietary power connector off the original PSU and fitted it to a modern 24Vdc 2A PSU, then tested the machine again – the speaker repeatedly “clicked” and the screen backlight flickered as though the unit was trying to start up but constantly restarting, probably due to the overload protection on the PSU kicking in repeatedly (this seems to be a running theme now).
I tested the unit on a current-limited benchtop supply, and this immediately current limits at 1A at 24Vdc, only providing about 5Vdc. I checked the mainboard with a thermal camera to help easily identify any shorts – the new 100uF 35V SMD electrolytic capacitors at PC1-PC5 were getting pretty hot, and the Schottky diode PD1 (marked IR3H) on the underside of the board near the battery connector was getting scorching hot.
I tested PD1 in-circuit, and it tested short-circuit; I removed it to test out-of-circuit in case it was not at fault, but it had indeed failed short-circuit, possibly due to the failing battery pack overloading the charge circuit; I replaced PD1 with a suitable 60V 3A Schottky rectifier diode (30BQ060), and the laptop now booted for the first time!
The electrolytic capacitors at PC1-PC5 which were previously hot were now cool – these were probably exposed to AC from the shorted rectifier diode. Thankfully this wasn’t for long and was only a low voltage, so I don’t think this will have caused any lasting damage.
The picture below on the right was when I installed a through-hole part for testing purposes as I didn’t have any SMD ones, I later replaced this.
I reassembled the laptop to be able to test it properly, and it booted onto its HDD!
Reassembly & Testing
Reassembling the PowerBook 1400 was just the opposite of its disassembly.
With the system reassembled, everything worked great! I’d say that this has been a very successful repair and restoration.
