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The address line test failure (error 5) is a bit tricky to precisely decode because it's an XOR of the contents of memory against the expected value. My guess would be that it wrote 0x00010000 to location 0x00010000, but when it read it back it got 0x00000000. This would be the point where it...

I have this copy of firmware 1.55 that was on my computer. I'm not really sure why I have it, I don't have any SIMCheck hardware.

Does it happen when less than 5MB of RAM is installed? Sometimes the mapper register ends up putting the backlight in the RAM area.

Well if removing the Brightness control panel does not change it, then I'm guessing it's not in there. It's more likely a patch in the System file since they could just bake it in at this point.

That's probably a topic that requires a much more detailed tutorial of some sort, but here's a quick one: Go to File -> Import File and select the binary. While you can import the file itself, it's usually easier to export the individual resources and just get the one containing the code you...

Technically you can change it, there is a block of four jumpers on the drive's PCB and the first three are the SCSI ID.

The Conner doesn't have anything special for termination, just pull-up resistors connected to the SCSI +5V.

Since they are 8-bit chips on a 16-bit bus, the two chips will be in the same address range. The error result it gives should be the bad bits. Convert the first four characters of the result from hexadecimal to binary, and the 1s will represent bad bits, starting from bit 0 on the right.

Assuming you're on the M5120, you're currently testing 8 chips at a time. You may need to test smaller ranges. Here is a table of memory ranges for the 32 RAM chips. Note the repeating values because B through E are for the low byte and F through J for the high byte. 1 2 3 4 B 00000000 -...

If I recall correctly the Portable uses the voltage drop through the charge MOSFET to determine when the charger is connected. It compares the charger side voltage with the battery side voltage, and if the charger side is higher then the power adapter must be connected. So for example, with just...

That would be the trace connecting the 1.2V reference to pretty much everything else. Here's what I have documented for RP201:

Error 14 is unfortunately the very first test/error that you can get, so it's hard to say what else might not be working, but getting to that point means many things are working at least. Since you're not always getting that far I would suspect some sort of power issue. Start with the most...

It wouldn't necessarily have to be a ROM patch, as you would have to find a point to insert the instruction. Ideally you'd want it to run when system resumes from sleep but not more than once, and I think patches only run when the OS is running. A regular extension of some sort might be easier.

There's a few different ways you could do it, simplest would be changing the command from "sound on, clear latch" to just "sound on". In ResEdit for example change 2B from 03 to 01:

The RAM speed issue is due to a DTACK register not being accessed when the system wakes from sleep. The last 4MB of RAM from 4MB-9MB is run differently due an unreleased expansion card system, and if that register is not accessed after the CPU GLU is reset then the DTACK delay will be much...

I think I see what's doing it in the Portable Control Panel 1.3. Included are two ROM patches, one replacing the BatWatch VBL task and one for the SndWatch VBL task I posted earlier. I believe the BatWatch patch is to add dimming of the backlight when the battery is low and a new message for...

The registers aren't really documented anywhere. I believe that bit switches between PWM and analog output on the ASC, but as you see the analog is not connected to anything at all. There was also a thought I had on the ripple from the 12V regulator. The design guide for the LT1070 recommends...

MicroBug is a much more basic version of MacsBug, I believe it is either built in to the ROM or the OS. It looks like this:

One thing you can experiment with as well with a debugger (you should at least have MicroBug included) is disabling the output on the Apple Sound Chip. Hit the programmer/interrupt button and type SM FB0802 1, then see if you notice a difference in the noise levels.

I tried booting from that same French MacTest Portable disk on mine and seem to have the exact same sound every 10 seconds. Yet if I boot from a System 6.0.8 "System Tools" disk that sound does not occur.