Editing Macintosh SE/30 Troubleshooting (section)

== 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&nbsp;V alone, remove the sound chips and wire up the headphone port so you can still hear audio:

[[File:SE-30 5v Power Bridge.png|thumb|312x312px|SE/30 +5&nbsp;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.<ref name="retrosixboot" />

=== 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.<ref name="retrosixboot" />