Macintosh SE Troubleshooting

Begin troubleshooting by confirming the analog board provides correct voltages: ideally, +5V DC (within 4.90–5.10V) and +12V DC at the floppy or SCSI drive connectors.

If the SE appears completely dead (no fan, CRT glow, or startup chime):

• Check analog board fuses, rectifiers (CR2, CR3), Q2 transistor, and R22 resistor
• Test voltages with a multimeter
• Disconnect any peripherals or internal cards
• Inspect logic board for corrosion or capacitor leakage
• Ensure reset and interrupt switches are not jammed
• Perform full capacitor replacement (recap) on the logic board

"Simasimac" – Horizontal Stripe Pattern

Macintosh Simasimac

The infamous Simasimac pattern (horizontal B&W stripes, no chime) usually means failed reset circuitry or RAM issues caused by leaky capacitors.

Steps to resolve:

• Clean and reseat ROM and RAM chips
• Replace PRAM battery if below 3.0V
• Verify CPU reset and 16 MHz clock with an oscilloscope
• Check continuity around capacitors for damaged traces
• Inspect the Apple Sound Chip (ASC) and RP2 filter network

Horrizontal Collapse - Single Horrizontal Line

Horrizontal collapse is common on both the Macintosh SE and the SE/30. Both devices share identical analog boards. It is extreamly important that you power off your Mac as soon as this happens, the concentrated line will cause permanent burn-in on the CRT phosphor in a matter of minutes. There are usually four culprets to this issue, P1 & J1 cracked joints (this is very common due to heat cycling of the solder over time), the C15 capacitor leaking or the R19 resistor failing. All of these components are on the analog board.

1. Check Solder Joints (P1 & J1 Connectors): The most common culprit is cracked or cold solder joints around the deflection yoke connector (usually labeled P1) and the flyback transformer area on the analog board. Use a soldering iron to reflow the solder on these pins.
2. Inspect/Replace C15: The non-polar film capacitor (C15, 3.9μF) on the analog board is a known failure point that causes horizontal collapse. Inspect the board for physical damage or leakage around this component.
3. Check the R19 Resistor: Check the R19 resistor (220 ohm) in the horizontal circuit; it may have burnt out and will need to be replaced if it shows signs of charring.

Chimes of Death and Sad Mac Codes

The Chimes of Death suggest serious logic board issues:

• Reseat and clean ROM SIMM and RAM modules
• Ensure memory banks are filled with identical SIMMs (4 per bank)
• Test RAM slots and address/data lines for continuity
• Replace faulty ICs like 74F258 multiplexers
• Severe cases may involve the VIA or ASC chips

See Sad Mac Error Codes for full interpretation of error patterns.

Video Display Issues

No Video but Chime Present

• Confirm CRT glow and brightness control
• Check for missing sync/video signals at P1 connector
• Suspect ICs like UE8 (video multiplexer)

Vertical "Jailbar" Stripes

• Caused by RAM misconfiguration
• Ensure matching SIMMs in each bank, larger ones in Bank A

Checkerboard Pattern

Checkerboard screen from logic board fault

• Indicates ROM or early memory failure
• Clean and reseat ROM SIMM
• Use compatible ROM for SE (not SE/30 or IIsi)

Disk Drive and SCSI Issues

Frozen Mouse on Gray Screen

• Suggests SCSI controller (NCR 53C80) failure
• Disconnect internal SCSI devices to test
• Replace SCSI chip if necessary

Floppy Drive Issues

• Clean mechanical components
• Check or replace the SWIM floppy controller
• Resolder or replace nearby ICs

More on this can be found at:

• Macintosh HDD Maintenance
• Macintosh Floppy Drive Maintenance

Audio and ADB Issues

Audio Issues

• No chime could mean bad ASC or analog amplifier
• Check headphone jack – if it works, analog board is likely at fault
• Replace ASC if digital audio fails

ADB Issues

• No keyboard/mouse? Check and replace:

 * Fuse F1
 * ADB microcontroller (Egret)

• Inspect solder joints on VIA chips and ADB port

Recurring Reset or Clock Failures

• Random resets = failing capacitors or shorted traces
• Clock loss = bad 32.768 kHz crystal or dead PRAM battery
• Clean up any electrolyte residue near ASC, VIA, or Egret chips

Analog Board Troubleshooting

• Vertical line only = horizontal deflection issue → reflow P1 pins, replace C15
• Horizontal line only = vertical collapse → check TDA1170A vertical IC
• Wavy display = failing flyback transformer
• Clicking power supply = logic board short or bad startup circuit (CR2/CR3, Q2, R22)

Power supply and startup

The SE was fitted with one of two switch-mode power supplies (an international/Astec type and a Sony type). A tired PSU shows as no start-up, a repeated ticking/clicking, or unstable rails; recap or substitute the supply and confirm +5 V (4.90–5.10 V) and +12 V before chasing logic-board faults. The SE shares its analog board with the Macintosh SE/30; the detailed analog-board and minimal-boot diagnostics on the Macintosh SE/30 Troubleshooting page apply directly.

PRAM battery

The SE carries a 3.6 V 1/2AA lithium PRAM battery on the logic board. Old cells leak, and the electrolyte corrodes nearby traces and vias; remove a leaking battery immediately, neutralise and clean the residue with isopropyl alcohol, and repair any broken traces before troubleshooting further. A flat battery loses the clock and settings and can cause boot hangs.

Recap first

Before chasing any intermittent fault on an SE, replace the electrolytic capacitors on the logic board and inspect the analog board. Leaking electrolytics cause a large share of compact-Mac faults — simasimac, no boot, distorted sound, video instability and random resets — and their residue corrodes traces.

Storage: SCSI and modern replacements

The SE uses the NCR 53C80 SCSI controller for its internal hard disc. Failing period drives (stiction, dead boards) are common; a modern solid-state replacement such as a BlueSCSI or SCSI2SD is the usual fix. Check the SCSI bus termination, and note that some SCSI adapters need termination power (TERMPWR) supplied to work reliably.

Related Pages

• Macintosh SE General Maintenance
• Macintosh HDD Maintenance
• Macintosh Floppy Drive Maintenance
• Sad Mac Error Codes