Documenting Apple's hidden 'Test Mode' to fix a dead SE/30 #repair

In my last SE/30 repair video, I was totally stuck with what to do next because the machine crashed as soon as I turned it on. That led me on a path to discover the internal ROM based Macintosh diagnostics which we can leverage to figure out what exactly is wrong with these broken SE/30 motherboards!

Part 2: This part!
Part 3: Coming soon

-- Links

Using internal Mac diagnostic modes:

Original document on the Diagnostic protocol:

Replicated Schematics of the SE/30:

Mac SE and SE/30 PicoATX PSU adapter:

RGB2HDMI:

TechStep Photos:

TechStep Replica:

Adrian's Digital Basement Merch store:

Adrian's Digital Basement ][ (Second Channel)

Support the channel on Patreon:

My GitHub repository:

-- Tools

Deoxit D5:

O-Ring Pick Set: (I use these to lift chips off boards)

Elenco Electronics LP-560 Logic Probe:

Hakko FR301 Desoldering Iron:

Rigol DS1054Z Four Channel Oscilloscope:

Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:

TL866II Plus Chip Tester and EPROM Programmer: (The MiniPro)

TS100 Soldering Iron:

EEVBlog 121GW Multimeter:

DSLogic Basic Logic Analyzer:

Magnetic Screw Holder:

Universal ZIP sockets: (clones, used on my ZIF-64 test machine)

RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)

Plato (Clone) Side Cutters: (Order Five)

Heat Sinks:

Little squeezy bottles: (available elsewhere too)

--- Instructional videos

My video on chip removal without damage:

--- Music

Intro music and other tracks by:
Nathan Divino
@itsnathandivino

[jandjrandr]

This is by far one of your most revolutionary videos for Mac II/SE diagnostics thus far. Kudos to you Adrian for this investigation!

[TonyHoyle]

It's wild to me that people knew it was a serial protocol for 30 years and nobody actually tried to use it (except that one guy who wrote the document) until now.

[scramble]

love these types of moments when you just happen to stumble across an old txt file that unlocks forgotten knowledge

[logiclust]

used to use a techstep back in the days of being a certified mac tech, however, our board-level repair techs could spot problems faster than the tool could expose them so rarely used the thing. You helped bring back a lot of fond memories of those years. it was the dawn of the PPC and the clone wars; we we had a lot of interesting hardware rolling through the shop. i loved apple's toolless industrial design back in those days, everything was so easy to work on.

[christianbauer]

This “test mode” is called the Serial Test Manager (STM), and the source code to a later version of it is included in the SuperMario sources (OS/StartMgr/UST*.a). So it should be possible to figure out exactly how all these tests work. 😉

[neonhomer]

Raise your hand if you wouldn’t mind a 2+ hour video from Adrian…. ✋

[JanusCycle]

Great find. I absolutely love complicated obscure inbuilt test modes like this. Thanks for exploring this and showing us. I hope the archive comes back up soon.

[snooks]

16:19 glad you got to IA before they went down. I guess this video might not have happened without it, goes to show how critical of a service it is

[tony]

It took me months to get a loan Techstep recreation to try and diagnose my Colour Classic - then comes Adrian Black with some serial commands I can run! Amazing! This will open so many doors. I still haven't diagnosed the CC, I suppose if the TechStep will come up with some unhelpful errors like the Bus Error, I might be able to dig a bit more into it. Thanks for that Sir! I'll mention your work in my video of course.

[terryarnone]

Enjoyed watching this video even though I do not own a MAC.

Your detective work and internet researching skills are top notch. This video teaches your viewers how to problem solve.

Two thumbs up!

[horusfalcon]

I"m glad for you and all the Mac mavens out there that you captured this before the Archive went down. They're still down as I type, and this is an excellent example of they kind of stuff we'll be missing without it.

[mariestarlight]

As a former systems admin/network admin, you made me nostalgic for null modem cables. When I was young using those to transfer files and even play Doom with another person was possible. As an admin, we used Serial all the time to configure devices, and these days you use usb to serial adapters. I still have a frankencable similar to your laplink cable, but it allows me to turn "null modem" off and on, and has both male and female adapters on both sides, so I have a 1-cable solution for any serial ports I come across. I even have an RJ45 adapter for all the networking equipment that uses serial over an RJ45 port.

[sahajsarup]

So much <3 for the reverse engineering work and making the info publicly available. It shouldn't be too difficult to write code that automates most of this instead of manually entering the specific codes into the serial terminal.

[insanelydigitalvids]

Well, who knew!! What an incredible discovery. I can see a future full of Raspberry Pi Mac diagnostic tools. Let the revolution begin!

[jasonatkin]

I passed on a complete Apple TechStep at a flea market for $40 about 15 years ago. Still kicking myself to this day for that one.

[phanthanhlaptop]

Absolutely amazing video! I never knew about the built-in diagnostic mode in the Mac SE/30, and your detailed explanation was super engaging. It’s like a treasure trove of knowledge for vintage Mac enthusiasts. Keep up the great work!

[hansvanderlinden]

Hello Adrian. It gave me much pleasure watching this SE/30 saga. My conclusion is that you took the right step, making this your full time job. You do it with an abundant amount of pleasure. You face tells it all. Not even mentioning your smart way of working. It freaking works.

[techsaverscomputerrepairca]

One of the reasons Apple implemented board level swaps was because of guys like me! I was harvesting the original Mac and Mac Plus ROMs for use in the Magic Sac and Spectre cartridges for the Atari ST. It was a really cool device which would give you a faster Mac with a larger screen, all for far less money than a Mac (a LOT less!). Floppy support was a problem at first, but by the time the Spectre GCR cart came out, the ST, which used a slight variation of MS-DOS's FAT format, could now read and write to Apple's GCR format.

A similar device came out for the Amiga, but I feel like the Atari implementation was better, if not cheaper overall.

I had another device that was an internal mod that had an NEC V20 (Intel 8086 and 8080 compatible) so my ST could run Mac, CP/M, MS-DOS, Windows 2 and GeoWorks). I was a pretty happy young man!

Maybe someone could loan Adrian a Spectre GCR so he could explore it in a future episode?

[falecore]

This series is excellent and confirms many of the frustrations I have encountered over the years when working on these boards. Thank you Adrian, you are an incredible resource to the community!

[robertfear]

Sir, never dissapointed by your videos. Good stuff. Appreciate the content. I have a working VIC-20 now (just passed to my youngest son, ) because of the motivation your videos gave me.