Macintosh 128K/512K Service Source

The Macintosh volume of Apple's Service Source is a 79-page service manual for the Macintosh 128K and Macintosh 512K; its cover is titled simply Macintosh. The PDF's creation date is 15 December 1995.

Specifications

Macintosh 128K and 512K specifications

Item	Value
CPU	Motorola 68000, 7.83 MHz, 32-bit internal data bus
Memory	128K or 512K RAM; 64K ROM; PRAM in a CMOS custom chip, 256 bytes, backed by a user-replaceable 4.5 V battery
Disk storage	Internal single-sided drive for 400K 3.5 in disks
Interfaces	External drive port (DB-19), mouse port (DE-9), keyboard (RJ-11, synchronous serial), two RS-232/RS-422 serial ports (DE-9)
Keyboard and mouse	58-key keyboard; mechanical mouse with optical shaft encoding at 3.54 pulses per mm (90 per inch)
Sound and video	Four-voice sound, 8-bit D/A conversion at a 22 kHz sampling rate; 9 in screen, 512 × 342 pixels
Electrical	105-125 V AC, 50-60 Hz, 60 W maximum
Size and weight	13.6 in (34.5 cm) high, 9.6 in (24.4 cm) wide, 10.9 in (27.6 cm) deep; 16 lb 8 oz (7.5 kg)

Contents

From the manual's running heads, with PDF page numbers.

• Basics: Overview (p. 3)
• Specifications: Processor (p. 5), Memory (p. 6), Disk Storage (p. 7), I/O Interfaces (p. 8), I/O Devices (p. 9), Sound and Video (p. 10), Electrical (p. 11), Physical (p. 12)
• Troubleshooting: General (p. 14), Symptom Charts (pp. 15-22) for video, drives, peripherals and miscellaneous faults
• Take Apart: Cover (p. 24), Power/Sweep Board (p. 28), Logic Board (p. 32), CRT (p. 36), Floppy Drive (p. 39), Chassis (p. 42)
• Upgrades: Floppy Drive Upgrade Kit (p. 45), Logic Board Upgrade Kit (p. 51), 400K Drive ROM Upgrade (p. 56)
• Adjustments: Voltage (p. 61), Yoke (p. 67), Tilt Adjustment (p. 69), Video (p. 74)
• Exploded View (pp. 78-79)

What it settles

Voltage adjustment

Apple's procedure, which is the source of the "+5 V 4.85-5.15 V / +12 V 11.90-12.75 V" figures:

1. Remove the cover. Set the voltmeter to its 20 V range.
2. Connect the Macintosh voltage test cable, Apple part number 077-0135, to the external drive port. Keep the rubber hoods on the test plugs: shorting them together can damage the computer.
3. Connect the black meter lead between the meter's ground terminal and the chassis.
4. Connect the orange test-cable lead to the meter, switch on, and adjust the voltage regulator on the power/sweep board to between 11.90 V and 12.75 V.
5. Switch off, move to the red lead, switch on, and adjust the regulator to between 4.85 V and 5.15 V.
6. Switch off and repeat both tests. If the board will not adjust so that both voltages are in tolerance, replace the power/sweep board.

Apple says to verify the voltages after replacing the logic board or the power/sweep board, and to use a mirror to see the screen rather than reaching round the machine. The upper +12 V limit is 12.75 V. The regulator is shown by position in a drawing and is not given a designator in this volume. The adjustment applies to machines with this power/sweep board (128K, 512K and, in its own manual, the Plus); the SE and later compact Macs have no equivalent in their Service Source Adjustments chapters.

Symptom charts

If the Macintosh beeps continuously and tries to power up, the first cure is the voltage adjustment, then disconnecting the internal drive, then the logic board. For smoke or odour, for no video, no audio and no drive activity once the cord, switch and fuse are checked, and as the last cure for continuous beeping, Apple warns that replacing only the power supply board may damage the new board, and says to replace the power supply board, logic board and internal drive together before switching on. Clicking or chirping leads first to the logic board cable and the voltage adjustment. A programmer's switch that resets the machine intermittently should be filed down by about 1/16 in.

Take apart and upgrades

The power/sweep board is removed only after discharging the CRT and removing the anode cap; Apple warns never to wear a grounding wrist strap until the CRT is discharged. An exchange power/sweep board goes back to Apple with its logic board cable, after the contrast knob and battery have been moved to the replacement. A replacement 512K logic board takes the original ROMs. The ROMs sit at D5 (ROM HI) and D8 (ROM LOW), notches towards the front. The floppy drive upgrade kit fits an 800K drive and new ROMs to a 512K and is not recommended for the 128K; the logic board upgrade kit, which requires the drive kit first, turns a 512K into a Mac Plus with 1 MB of RAM; and later 400K drives with a new stepper motor need the 400K drive ROM upgrade.

Video adjustment

Contrast fully clockwise, brightness down until white lines appear and then up until they just vanish, contrast back 1/8 turn. Raster size is 7 in (177.8 mm) wide by 4.7 in (119.4 mm) high. Focus is turned clockwise to its limit and back 1/8 turn. Video adjustment is needed whenever the CRT or power/sweep board is replaced.

Exploded view

Part numbers as printed include CRT and yoke assembly 076-0103, power/sweep board 661-76214, logic board 661-06236, floppy drive 661-7615 (400K) or 661-0345 (800K), internal drive cable 590-0167 or 590-0437, CRT socket cable 590-0160, RFI shroud 805-0577, rear housing 630-5139 and front bezel 810-0373.

What this manual does not contain

There is no schematic, no component values, no capacitor list and no fuse rating. The electrical specification covers the 105-125 V machine only.

Pages that cite this document

• Macintosh 128K, Macintosh 512K, Macintosh 512Ke
• Macintosh 128K/512K General Maintenance, Macintosh 128K/512K Troubleshooting, Macintosh 128K/512K Capacitor Replacement Guide
• Macintosh Plus Service Source, Macintosh Portable Service Source
• Chilton's Guide to Macintosh Repair and Maintenance
• Inside Macintosh Volumes I-II-III 1985

Apple's Take Apart chapter opens with a warning about the high voltage and the high-vacuum picture tube; see CRT Discharge Procedure before working inside one.

Download: Macintosh 128k.512k.pdf