Macintosh Portable (backlit)
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| The backlit display's inverter board and CCFL cable, from Apple's Service Source | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | Portable computer |
| Released | 11 February 1991 |
| Discontinued | October 1991 |
| Intro price | US$4,199 (2 MB, 40 MB hard disk); US$4,699 (4 MB) |
| CPU | Motorola 68HC000 at 15.6672 MHz |
| Memory | 1 MB on the logic board plus a pseudostatic RAM card; 2 or 4 MB as sold, 8 MB maximum |
| Storage | 1.4 MB floppy drive; 40 MB SCSI hard disk |
| Display | Backlit 10-inch active-matrix LCD, 640 × 400, monochrome |
| Sound | — |
| ROM | 256 KB |
| OS / Firmware | System 6.0.4 to System 7.5.5 |
| Predecessor | Macintosh Portable |
| Model no. | M5126 |
The Macintosh Portable (backlit), model M5126, is the revision of the Macintosh Portable that Apple introduced on 11 February 1991. It adds a backlight to the active-matrix screen and replaces the original's static RAM with cheaper pseudostatic RAM. It was sold with 2 MB or 4 MB of memory and a 40 MB hard disk, at a lower price than the original, until the PowerBooks replaced it in October 1991.[1][2] Everything not listed below is as on the original; the shared repair guides cover both.
Differences from the original
[edit | edit source]| Item | Original | Backlit |
|---|---|---|
| Display | Reflective LCD, 661-0473; software contrast control | Backlit LCD, 661-0647, with CCFL and inverter board; software brightness control[3] |
| Logic board | Static RAM, 820-0219-A; service part 661-0470 or 661-1610 | Pseudostatic RAM, 820-0256[3][4] |
| Wait states | 1 | 10[3] |
| RAM cards | Static RAM, 1 to 8 MB, 9 MB maximum | Pseudostatic RAM, 1 to 7 MB, 8 MB maximum; RAM connector notched[3][5] |
| Power regulation | Separate hybrid module | Circuit on the logic board[6] |
| Battery life | Up to 10 hours | Shorter: the pseudostatic RAM and the backlight draw more power[1] |
Static and pseudostatic RAM cards are not interchangeable. Apple's check is the RAM connector on the logic board: if it has a notch, fit a pseudostatic card.[3]
The ROM is the same in both models. Software tells them apart by reading the byte at address $FC0200, which returns $A5, $A3 or $AD on a backlit machine; David Cook's non-backlit machine returned $E1. Apple's Portable 1.3 control panel uses this to decide whether to load the backlight driver.[7] Apple's symptom chart for a backlight that cannot be adjusted or does not light starts with "Use version 1.3 of Portable CDEV", then the inverter connections, the inverter board, the display and the logic board.[3]
The A23 bodge wire
[edit | edit source]Backlit logic boards carry a factory modification: a cut trace and a bodge wire from the CPU's address line A23 to a NAND gate in the backlight identification circuit. AppleTree, who traced the circuit after "repairing" the cut trace and getting a machine that would not boot, explains it. The identifier was first gated by the slot chip-select alone, which also fires for memory-card addresses, so Apple added A23 to keep the identifier off the data bus during RAM reads. That leaves the top megabyte of card addresses ($800000-$8FFFFF) unusable, which is why the backlit model stops at 8 MB. Do not bridge the cut trace near the 74AC00, and leave the wire in place.[8]
Backlit display upgrade for the original Portable
[edit | edit source]Apple offered owners of the original Portable a backlit display upgrade. The kit is a ROM card, which plugs into the ROM slot at the back of the logic board with its connector facing forward, an 8-wire cable from the card to the display, and the backlit display. Apple's procedure warns that a RAM disk's contents are lost, so save them first, and calls for System 6.0.5 or later.[3] Low End Mac gives the dealer-installed price as US$1,095 and the card's part number as 820-0318-B.[9] An upgraded original keeps its static RAM board and 9 MB limit.[3][5]
Known problems
[edit | edit source]- "No reserve battery power" at startup, with a battery that reads 0 % in the battery menu although it measures about 6 V: on one M5126 the cause was a via eaten by capacitor leakage under a resistor array, which also put more than 6 V with heavy ripple on the 5 V rail. techknight adds that the trace from the negative side of a nearby 47 µF capacitor to R208 can open.[10]
- A speaker tick every 10 seconds, reported by JDW and David Cook on their M5126 machines. It appears with Portable control panel 1.3 or later, or System 7 or later, because Apple's sound-power check writes to the power manager every 10 seconds even when sound power is already on. David Cook's Quiet Portable extension replaces that code.[11]
- Faulty pixels: Apple accepts up to five pixels that never turn on, and none that stay black.[3]
The capacitor list for this board is on Macintosh Portable Capacitor Replacement Guide.
Maintenance and repair
[edit | edit source]- Macintosh Portable General Maintenance
- Macintosh Portable Troubleshooting
- Macintosh Portable Capacitor Replacement Guide
- Macintosh Portable Battery Replacement
- Macintosh Portable Service Source
References
[edit | edit source]- ↑ 1.0 1.1 Low End Mac, "Backlit Mac Portable" (retrieved 2026-10-02). Introduced 11 February 1991; model M5126; backlit screen; 2 MB or 4 MB, expandable to 8 MB with a pseudo-SRAM card; pseudo-SRAM and backlighting reduce battery life; replaced by the PowerBook 100, 140 and 170 in October 1991; cautions on HD SC Setup, battery discharge and hard drive spin-up. Secondary source.
- ↑ Wikipedia, "Macintosh Portable" (retrieved 2026-10-02). Backlit model introduced 11 February 1991 at US$4,199 (2 MB, 40 MB) and US$4,699 (4 MB, 40 MB). Used for dates and prices only.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Apple Computer, Macintosh Portable Service Source, hosted here as File:Macintosh_portable.pdf (see Macintosh Portable Service Source). PDF page numbers: Processor p. 5; Memory p. 6; Sound and Video p. 12; Symptom Charts, Video p. 23; Take Apart: LCD Display (Backlit) pp. 82-91; Upgrades: RAM Expansion pp. 121-123, Backlit Display Upgrade pp. 127-131; Exploded View p. 151.
- ↑ Console5 TechWiki, "Macintosh Portable" (retrieved 2026-10-02). Board numbers 820-0219-A and 820-0256-03/820-0256-B with capacitor lists. Secondary source.
- ↑ 5.0 5.1 Apple Computer, Apple Memory Guide (May 2000), hosted here as File:Apple Memory Guide (May 2000).pdf (see Apple Memory Guide). Portables pp. 1-2 (PDF pp. 98-99).
- ↑ TinkerDifferent forum thread "GOTCHAS when buying a Macintosh Portable?", July 2023. Androda: the backlit Portable has the hybrid's circuit on the motherboard, next to the keyboard and trackball connector capacitors. Secondary source.
- ↑ TinkerDifferent forum thread "Portable and PowerBook 100 Technical Note: PRAM, Backlight, and ROM Diff", David Cook, January 2026. Secondary source.
- ↑ TinkerDifferent forum thread "I broke and fixed Macintosh Portable (backlight). Attached backlight circuit schematic that I reverse engineered", AppleTree and David Cook, June 2026. Community repair report. Secondary source.
- ↑ Low End Mac, "Mac Portable" (retrieved 2026-10-02). Backlight upgrade, dealer-installed, US$1,095; card 820-0318-B. Secondary source.
- ↑ TinkerDifferent forum thread "Macintosh Portable M5126 - Battery problem - Good night :0)", Scouter3D and techknight, August 2026. Community repair report. Secondary source.
- ↑ TinkerDifferent forum thread "Fixing a Macintosh Portable - What worked for me", David Cook, JDW and others, January to August 2026. Secondary source.