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.

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.
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.
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

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)