Macintosh Plus

For more information, see this article's corresponding Wikipedia page: Macintosh Plus.

This device is in the WorkNeeded:OriginalParts category because it was flagged as missing information on the original parts. It may have replacement parts listed but those cannot be assumed to be identical to the originals. If you have a list of the original parts, please feel free to add them by copying the relevant table from EditorsToolbox:Tables

This device is in the WorkNeeded:General category because it was flagged as missing general information about the device. The information may be incomplete, using default text, or inaccurate and should be verified with external sources if possible. If you can add or correct information on this page, please feel free to edit it and do so.

Macintosh Plus

Preliminary Information
Release Year	1986
Leak Risk	Medium
Batteries	Removable
Mounting Technology	Through Hole, SMD, Sockets
Capacitor Types	Aluminum Electrolytic, Foil
Destructive Entry	No
CRT Guides
General Information · Repair Cautions

This page applies to the Macintosh Plus primarily, but information here might also be relevant for the 128 and 512 variants.

Warning: While running, the voltages on the analog board and around the CRT can be lethal.

Known Issues

Wobbly / wavy / shaking screen

The computer might work fine otherwise and boot, or the screen only shows garbage. But whatever is displayed is unstable, with the outer lines of the display swaying back and forth at about 10Hz.

Causes

1. Unstable or too low voltage from the power supply on the analog board.

Solutions

1. Confirm correct voltage

Turn on the computer and measure the voltage on the 12V rail, which is most easily done by measuring the voltage between pins 7 or 8 on the external floppy connector to pin 1 or the chassis ground. It is specified it to be within 11.9 and 12.75 Volts. Then check the 5V rail via pin 6 on the same connector, which should be between 4.85 to 5.15 Volts.

2. If voltage is too low

The output voltages of the power supply can be controlled by a variable resistor on the analog board. After removing the computer case, it is adjustable using a flat-head screw driver through a hole in the board. Look for the hole marked "Voltage" on the protective sheet on the analog board, just above the speaker holes.

If the voltages are out of spec, adjust the resistor while the computer is running and you're measuring the voltage. First get 12V within spec, as the 5V rail is derived from it.

3. If the voltage is unstable or cannot be adjusted

If adjusting the resistor doesn't make any difference, double check that you're turning the right control. If that's the case, it is possible that the optocoupler used in the feedback circuitry of the power supply is faulty, and thus the variable resistor is without effect. The voltages will also be very low, around 9-10V on the 12V rail and 3V on 5V. It's the small 6-legged DIP chip found just above the brightness control knob, at the bottom of the analog board, marked U3.

1. Using diode mode on a multimeter, measure between its pins 1 (where the dot is) and 2. It should leave some current flow in one direction, but fully block when you flip the test leads. If there's no continuity in both directions, the internal LED is dead. The chip needs replacing. (Note: Maybe there are other failure modes and even if this checks out, it's might be worth replacing just in case.)
2. While it may not look like it, the chip is likely to be socketed. Try gently prying it out of the board. If it doesn't budge, desolder it.
3. A 4N35 optocoupler is a cheap and widely available drop-in replacement.

Once the optocoupler is replaced, turn down the voltage to minimum before trying again. Better to under- than to overvolt the system.

Original Parts

630-1012 Analog Board US VERSION

*Note: C1 is highly likely to fail*

Capacitor Specifications and Footprint Information

RefDes	Qty	Capacitance	Voltage	Mount	Diameter/Size	Height	Lead Spacing	Temp	Type	Brand	Series
C1	1	3.9 µF	100 V	Through Hole Radial				85 °C	Aluminum Electrolytic		Standard
C2	1	4700 µF	16 V	Through Hole Radial				85 °C	Aluminum Electrolytic		Standard
C3, C30	1	220 µF	16 V	Through Hole Radial				105	Aluminum Electrolytic		Low ESR
C4, C40	2	33 nF	400 V	Through Hole Radial					Metallized Film
C5	1	47 µF	10 V	Through Hole Radial				85	Aluminum Electrolytic		Standard
C6, C14	2	22 µF	50 V	Through Hole Radial				85	Aluminum Electrolytic		Standard
C7, C8	2	10nF	1000 V	Through Hole Radial					Ceramic Disc
C9	1	10 µF	160 V	Through Hole Radial/Axial				85	Aluminum Electrolytic		Standard
C10	1	220 nF	100 V	Through Hole Radial					Metallized Polyester
C11, C13	2	33 µF	16 V	Through Hole Radial				105	Aluminum Electrolytic		Low ESR
C12, C19, C20, C41	4	10 nF	400 V	Through Hole Radial					Metallized Polyester
C15, C16, C17	3	10 nF	1500 V	Through Hole Radial					Ceramic Disc
C18, C22, C23, C28	4	0.1 µF	50 V	Through Hole Axial					Encapsulated Ceramic
C21, C42	2	0.1 µF	100 V	Through Hole Radial					Metallized Polyester
C24, C29	2	2200 µF	10 V	Through Hole Radial				105	Aluminum Electrolytic		Low ESR
C25, C26, C31	3	1000 µF	16 V	Through Hole Radial				105	Aluminum Electrolytic		105 Deg Standard
C27	1	22 nF	400 V	Through Hole Radial					Metallized Polyester
C33, C37	2	4.7nF	400 V	Through Hole Radial					Film or Ceramic
C35, C36	2	100 µF	250 V	Through Hole Radial				85	Aluminum Electrolytic		Standard
C38	1	0.1 µF	250 V	Through Hole Radial					Film or Ceramic
C39	1	470 µF	10 V	Through Hole Radial				85	Aluminum Electrolytic		Standard
C43	1	470 µF	16 V	Through Hole Radial				85	Aluminum Electrolytic		Standard

Analog Board capacitor specifications copied from this spreadsheet

Replacement Parts

630-1012 Analog Board US Version

Capacitors

RefDes	Qty	Compatible Part Number	Order Links
C1	1	ECW-FD2W395K	DigiKey Mouser
C2	1	16PK4700MEFC12.5X25 / ESK478M025AM2AA	DigiKey Mouser
C3, C30	1	860240475007	DigiKey Mouser
C4, C40	2	333MMR400K / 333MSR630K	DigiKey Mouser
C5	1	860010272003	DigiKey Mouser
C6, C14	2	860020672011	DigiKey Mouser
C7, C8	2	S103M47Z5UN63J7R / CK45-E3DD103ZYVNA	DigiKey Mouser
C9	1	UVR2C100MPD	DigiKey Mouser
C10	1	223MMR630K	DigiKey Mouser
C11, C13	2	860080572001	DigiKey Mouser
C12, C19, C20, C41	4	103MMR630K	DigiKey Mouser
C15, C16, C17	3	CK45-E3DD103ZYGNA / CK45-E3DD103ZYVNA	DigiKey Mouser
C18, C22, C23, C28	4	C410C103K5R5TA / YV101103Z060HAND5P	DigiKey Mouser
C21, C42	2	ECQ-E2103KF / MKS2G021001A00MSSD	DigiKey Mouser
C24, C29	2	UPW1V222MHD	DigiKey Mouser
C25, C26, C31	3	860240580011	DigiKey Mouser
C27	1	223MMR630K	DigiKey Mouser
C33, C37	2	C971U472MVWDBA7317	DigiKey Mouser
C35, C36	2	EKXJ251ELL101ML20S	DigiKey Mouser
C38	1	C981U103MZVDBA7317	DigiKey Mouser
C39	1	860010273011	DigiKey Mouser
C43	1	860020374012	DigiKey Mouser

Disassembly Notes

Warning: While running, the voltages on the analog board and around the CRT can be lethal.