Macintosh SE/30 Troubleshooting

This guide provides solutions to common faults experienced in the Macintosh SE/30. From power issues to Simasimac patterns and SCSI failures, these diagnostics will help identify, isolate, and resolve problems.

Preliminary Checks and Power Supply Basics

Begin by verifying the analog board delivers proper voltages:

+5V rail: 4.90V – 5.10V
+12V rail: Confirmed at floppy or hard drive connectors

If the unit is completely dead (no fan, CRT glow, or chime), inspect:

Fuses
Rectifiers CR2 and CR3
Transistor Q2
Resistor R22

Also:

Disconnect external peripherals and cards
Check logic board for PRAM battery corrosion
Replace all electrolytic capacitors on the logic board

"Simasimac" – Horizontal Stripe Pattern

Macintosh SE/30 Simasimac pattern

The infamous "Simasimac" pattern shows horizontal black-and-white lines with no startup chime. Causes include:

Leaking capacitors disrupting the reset circuit
Corroded traces or vias near RAM/ROM

Solutions:

Clean and reseat ROM and RAM SIMMs
Replace PRAM battery if < 3V
Check for reset pulse at CPU
Test for 16 MHz clock at CPU
Inspect Apple Sound Chip (ASC) at UB11 and filter RP2
Use multimeter or oscilloscope to confirm continuity

Chimes of Death and Sad Mac Codes

The Chimes of Death signify early boot failure—commonly RAM or ROM faults.

Checklist:

Use 4 matched SIMMs per bank
Larger-capacity SIMMs go in Bank A
Clean/reseat ROM SIMM
Check address/data continuity near capacitors
Replace 74F258 multiplexers or RAM if needed
Check VIA chips for overheating or corrosion

See: Sad Mac Error Codes for detailed interpretation.

Video Display Issues

No Video but Chime Present

Verify brightness knob
Confirm CRT glow
Check UE8 (video multiplexer)
Probe video/sync signals at P1 connector

Vertical "Jailbar" Stripes

Indicates incorrect RAM configuration
Use identical SIMMs per bank (larger ones in Bank A)

Checkerboard Pattern

Checkerboard error screen

Typically a ROM failure
Clean/reseat the ROM SIMM
Confirm compatibility (use SE/30 or IIsi ROMs only)

Disk Drive and SCSI Issues

Frozen Mouse on Gray Screen

Possible failure of SCSI controller (NCR 53C80)
Disconnect all internal/external SCSI devices
Inspect and replace termination resistors

Floppy Drive Issues

Dirty mechanism
Faulty SWIM controller
Cold solder joints on VIA or SWIM ICs

For more, see:

Audio and ADB Issues

No Sound

Test audio at the headphone jack
Inspect ASC (Apple Sound Chip)
Inspect analog board audio amplifier

ADB Malfunction

Blown fuse F1
Failed ADB microcontroller (Egret)
VIA chip solder cracks or corrosion

Reset and Clock Problems

Random resets: Check power rail stability
No time retention: Dead PRAM battery or failed 32.768 kHz crystal
Check surrounding electrolyte residue near Egret or VIA chips

Brief Analog Board Troubleshooting

Vertical line only: Horizontal deflection fault – reflow P1 connector and replace C15
Horizontal line only: Vertical deflection fault – reflow P1 and replace TDA1170A
Wavy or distorted video: Failing flyback transformer
PSU clicking repeatedly: Shorted logic board or failed CR2, CR3, Q2, or R22