Macintosh SE/30 Troubleshooting

This guide covers the faults an SE/30 actually presents with: dead machines, the simasimac pattern, collapsed rasters, Chimes of Death, SCSI and floppy problems, and the bench technique for bringing a board up from nothing.

Before diagnosing anything electronic, deal with the leakage. Every SE/30 has leaking surface-mount electrolytics on the logic board, and the electrolyte is conductive and corrosive. A great many "faulty chip" diagnoses on this machine turn out to be a severed trace or a corroded via. Recap and clean first, then troubleshoot — see Macintosh SE/30 Capacitor Replacement Guide.

Preliminary Checks and Power Supply Basics

The SE/30 has three separate modules behind the logic board: a power supply (Apple 661-0370), an analogue board (661-0371) and a video board (982-0024). All three are shared with the Macintosh SE. Knowing which one you are accusing matters.

Apple rates the machine at 120–240 V AC, automatically configured, 48–62 Hz, 75 W maximum. Apple's Service Source publishes no rail tolerances and no voltage adjustment procedure for the SE/30 — there is no trimmer to turn. Its symptom chart sends a completely dark machine with a stopped fan to the power supply first, then the analogue board.

Macintosh SE/30 logic board analogue connector (front)	Macintosh SE/30 logic board analogue connector (back)

If the unit is completely dead — no fan, no CRT glow, no chime — the analogue board is the usual culprit, and Larry Pina narrows it to specific components:

• A dreadful hissing or sizzling noise with a dark screen — rectifier CR2 shorted (0.00–0.01 Ω). It is a GI854 barrel rectifier, R-51, 600 V 3 A; Pina fits an MR824 (R-51, 400 V, 5 A) instead to stop it recurring.
• Dead with no hissing noise — rectifier CR3 shorted, same part. Then check the BU4060 horizontal output transistor at Q2 for burning, and after that the flyback at T2.

Also worth doing before anything else:

• Disconnect every external peripheral and any PDS card.
• Check the logic board for PRAM battery corrosion, and remove the cell. Apple's threshold for replacement is below 2.8 V.
• Replace all of the electrolytic capacitors on the logic board and check trace continuity around every one of them.

Power Rails

The logic board takes power and video through J12, Apple's "Power & Video Connector", a 14-way header. The pinout below is from Apple engineering drawing 050-0253-01 as redrawn by the macse30mlb project, and has been checked pin by pin against that schematic.

J12 — power and video connector

Pin	Signal
1–5	Ground
6	−5 V
7	−12 V
8	Ground
9	Video out
10	Horizontal sync
11	Vertical sync
12, 13	+5 V
14	+12 V

That pinout makes bench-powering a bare logic board practical, and it tells you what each rail is for:

• +12 V (pin 14) feeds the internal and external floppy drives, the PDS connector and the sound circuit — J6, J8, J13 and UB10/UB11/UA9. A board will come up to a point without it, but the sound chip UB11 will hold the system in reset, so the furthest you will get is horizontal lines or a simasimac screen.
• −12 V (pin 7) goes only to the PDS slot (J13), so a bare board boots without it.
• −5 V (pin 6) feeds the printer and modem line drivers (UE12, UD12) and the PDS slot, so a bare board boots without it too.
• +5 V (pins 12 and 13) goes everywhere else. It is not optional.

With +5 V alone you should see video output on pins 9, 10 and 11 on an oscilloscope, but the machine will not progress past horizontal lines because UB11 holds !RESET at around 2.5 V. Add +12 V to get further.

"Simasimac" — Horizontal Stripe Pattern

Macintosh SE/30 simasimac pattern

The simasimac pattern — alternating horizontal black-and-white bands with no startup chime — is not a video fault. The video circuit is running perfectly; it is drawing whatever happens to be in video memory because the processor never got out of reset or never completed its startup tests. On an SE/30 the cause is nearly always leakage damage.

Work through:

• Recap and clean the logic board first. Everything below is wasted effort on a board still covered in electrolyte.
• Check continuity on traces and vias around every capacitor, particularly under the Ux8 row and around the sound chips.
• Clean and reseat the ROM SIMM and the RAM SIMMs.
• Check that the CPU is being released from reset (see The !RESET line below); a sound chip with no 12 V rail, or a failed one, will hold it down.
• Check the processor clock. Apple specifies the SE/30's 68030 at 15.667 MHz — commonly rounded to 16 MHz in conversation, but the figure to expect on a counter is 15.667.
• Inspect the Apple Sound Chip at UE10 and the Sony sound chip at UB11, and the resistor pack RP2 beside them.
• Replace the PRAM cell if it reads below 2.8 V.

Single Vertical Line — Horizontal Sweep Collapse

A picture that has collapsed to a single vertical line is a failure of the horizontal sweep. This is common on both the Macintosh SE and the SE/30, which share an analogue board.

Switch the machine off the moment you see it. A concentrated line will burn the phosphor permanently within minutes.

The culprits, in the order worth checking:

1. Cracked joints at the yoke connector (P1 / J1). Thermal cycling over decades fatigues these joints, and this is by a wide margin the most common analogue-board fault on a compact Mac. Reflow all four pins with fresh solder while the connector halves are still mated, or the heat will distort the plastic and you will not get them back together. Pina also notes the plug itself is often burned by this stage and may need replacing.
2. C15. The non-polarised high-frequency capacitor in the horizontal circuit, 3.9 µF 35 V bipolar low-ESR. Pina specifies it as 3.9 µF NP 25/35 V HF and recommends replacing it with a 3.9 µF NP 100 V HF part. Its failure shows first as poor horizontal linearity — items on the left wider than items on the right — then as a bright vertical line, then as smoke.
3. R19. 220 Ω, ½ W, 5 %. When it burns out the machine chimes normally but shows a relatively dim vertical line. Pina adds that linearity coil L3 should be vacuum-desoldered and resoldered with fresh solder at the same time, or the fault returns.

A single horizontal line is the opposite fault — a collapse of the vertical sweep, a different circuit. Apple adopted the TDA1170 vertical deflection IC on the compact Macs after the Plus, and that is where to look.

Chimes of Death and Sad Mac Codes

The Chimes of Death signify a failure during the startup memory tests — usually RAM, ROM or the paths between them and the processor.

• Use four matched SIMMs per bank; put the larger-capacity pair in Bank A.
• Clean and reseat the ROM SIMM.
• Check address and data continuity around the capacitors — on an SE/30 a broken trace mimics a failed chip exactly.
• Suspect the F258 RAM multiplexers above the ROM slot. Recap-a-Mac reports these failing increasingly often, and the symptom is Sad Mac chimes with known-good RAM.
• Check the VIAs for corrosion and overheating.

The Sad Mac code on screen narrows this down considerably. See Sad Mac Error Codes — the decoding there is original research native to this wiki.

Video Display Issues

Apple's own symptom chart is module-level, but it establishes the order of suspicion: a dark screen with working audio and drives goes brightness control, video cable, analogue board, video board, logic board, CRT; a bright screen with no video information goes analogue board, video board, logic board.

No video but chime present

• Turn the brightness control clockwise. Apple lists this first for a reason.
• Confirm the CRT filament is glowing.
• Check the video multiplexer circuit — the row of Ux8 ICs below the large axial capacitor is a known casualty of capacitor leakage.
• Probe video and sync at J12 pins 9, 10 and 11.
• If the machine chimes, the fan turns and a hard disk spins but the screen stays dark and the brightness control does nothing, check R22 on the analogue board — 470 kΩ, ½ W, 5 %, which fails open.

Vertical "jailbar" stripes

• Usually a RAM configuration problem: use identical SIMMs in each bank, larger pair in Bank A.

Checkerboard pattern

Checkerboard error screen

• Typically a ROM failure. Clean and reseat the ROM SIMM.
• Confirm the ROM is the right one — an SE/30 or IIsi ROM.

Disk Drive and SCSI Issues

Frozen mouse on a grey screen

• Suspect the SCSI controller. The SE/30 uses an NCR 53C80 at UI12.
• Disconnect every internal and external SCSI device and retry.
• Inspect the termination resistors.

Floppy drive issues

• A dirty or dried-out mechanism is the most common cause by far — see Macintosh Floppy Drive Maintenance.
• The SWIM controller is at UJ11.
• Cracked or corroded joints on the VIA and SWIM packages.

Audio and ADB Issues

No sound

• The SE/30 has two sound ICs: the Apple Sound Chip at UE10 and the Sony sound chip at UB11. Both sit in an area that capacitor leakage reaches, and audio faults after leakage are common.
• Test at the headphone jack to separate the logic board from the internal speaker and the analogue board's amplifier.

ADB not working

• Fuse F1 on the logic board is a 1 A fuse; a dead keyboard and mouse on an otherwise healthy machine is very often this.
• The ADB transceiver is at UL11.
• Cracked or corroded joints on the VIAs.

Reset and Clock Problems

• Random resets — check rail stability at J12.
• Time not retained — a dead PRAM cell, or the 32.768 kHz crystal Y1.
• Look for electrolyte residue around the ADB transceiver and the VIAs.

Check the crystals first, because almost nothing on the board works without them. On an oscilloscope, Y1 (the crystal nearest the ROM, front right) should show a 32.768 kHz sine wave, squarer on the top pad, around 3–4 V peak to peak. (Waveform amplitude measured on the bench for this wiki; the crystal frequency is from the schematic.)

The !RESET line

The video output circuit runs regardless of the state of the reset line — which is why you can see horizontal lines or simasimac on a board that is going nowhere — but nothing useful happens until the processor is released from reset.

!RESET connects to:

• 68030 CPU (UK8) — bidirectional
• VIA1 (UK12) pin 37
• VIA2 (UK11) pin 37
• ADB transceiver (UL11) pin 4
• SWIM floppy controller (UJ11) pin 25
• 53C80 SCSI controller (UI12) pin 7
• Apple Sound Chip (UE10) pin 40
• Sony sound chip (UB11) pin 5

Any of these can hold !RESET low if it has failed, even where the pin is nominally an input.

Minimal Boot Requirements

If there is no bus activity, no chime and no video, start from the absolute minimum and look for the address bus toggling continuously at power-up, or for the startup chime.

The initial startup is handled by the glue logic chip UI8.

Critical ICs

• 68030 CPU (UK8)
• Glue logic (UI8)
• RAM signals PAL (UH7)
• 68k / video signals PAL (UI6)
• Pull-up resistor packs (RP7, RP9)
• Sound IC (UE10)
• ROM (J14) if you want to hear the startup sounds; otherwise watch the address bus on a scope

To run from +5 V alone, remove the sound chips and wire up the headphone port so you can still hear audio:

SE/30 +5 V power bridge

• Remove UB10 and UB11.
• Bridge UB11 pins 8 and 9 to tie the analogue and digital grounds together. Audio will be a little noisy. This also restores the S2 NMI button, which stops working once UB11 is out because the analogue and digital grounds are separated and the button uses the disconnected one. Note: S1, the normal reset button, will not work with UB10 removed — UB10 senses that button and pulls reset low. Use S2 or cycle the power instead.

Non-essential ICs

If a failing chip is dragging a rail or a bus line down, these can all come out:

• UD1
• UK4 (RTC)
• UD12 / UE12 / UG12 / UI12
• UK12 / UJ11 / UK11 / UL11
• UI5 (FPU)
• All RAM — if the board passes its RAM check but UG12, UI12 or UJ11 are missing or faulty you will get no beep and horizontal lines
• UK6 (video IC)
• UE6 / UG6 / UE7 / UG7 (PALs)
• UC6 / UC7 (video RAM)
• UA8 / UB8 / UC8 / UD8 / UE8 / UF8 / UG8
• UI2 / UJ2 / UI3 / UJ3 / UJ4 / UI4 / UJ6 (logic)
• RP1 / RP4 / RP5 / RP6 / RP8 (resistor packs)

Expected result

With only the critical ICs fitted, the sound chip removed and the headphone jack bridged, applying power should produce a Sad Mac boot sound. Without a ROM fitted, probe the lower address pins of the ROM socket instead — they should pulse continuously.

If neither happens, check that every chip on the !RESET list above is letting the line go high.

Initial Boot Sequence

Once the glue logic chip has brought the 68030's pins to their initial state, the processor starts walking the bus, and the address pins toggle continuously as it loops attempting a load.

The 68030's reset signal is bidirectional: it can both assert reset and be reset from outside. The minimum needed to see activity is:

• VCC at 5 V
• A valid clock
• !RESET high
• !HALT high

Macintosh SE/30 68030 pinout and diagram

!BERR

When the 68030 accesses memory or an I/O device and something goes wrong — a bad access, a parity error, a missing data acknowledge — a bus error is generated. Whichever device the processor was talking to pulls !BERR low, and the processor stops and enters its error handler. !BERR toggling low is therefore a sign that something on the address or data bus is unhappy.

On the SE/30, !BERR connects to:

• 68030 CPU (UK8)
• PAL1644B (UI6)
• Glue chip (UI8)
• PDS header (J13)

It is pulled up to +5 V through resistor pack RP7 (1 kΩ), so verify that pack is present and pulling high before reading anything into the signal. Since !BERR is an input to the processor and the PDS header is normally empty during a bare-board boot, the glue chip or the PAL is what must be driving it low.

Analogue Board Fault Summary

Symptom	Where to look
Single vertical line	Horizontal sweep collapse — reflow the yoke plug P1, then C15 (3.9 µF NP), then R19 (220 Ω) and linearity coil L3
Single horizontal line	Vertical sweep collapse — the TDA1170 vertical deflection IC and its surrounding circuit
Chimes, fan and drive run, screen dark, brightness has no effect	R22 open (470 kΩ, ½ W, 5 %)
Right side of the picture shakes during disk access or when a window opens	CR2, then Q2 (BU4060)
Dead with a hissing or sizzling noise	CR2 shorted
Dead with no noise at all	CR3 shorted, then Q2, then flyback T2
Wavy or distorted picture, high-pitched noise	Failing flyback

Related Pages

• Macintosh SE/30
• Macintosh SE/30 General Maintenance
• Macintosh SE/30 Capacitor Replacement Guide
• Macintosh SE Capacitor Replacement Guide
• Macintosh SE/30 Logic Board Schematic
• Sad Mac Error Codes
• Capacitor Failure Symptoms
• Battery Explosion, Capacitor or Corrosion Damage
• CRT Discharge Procedure
• Macintosh Floppy Drive Maintenance