Logic Board - Macintosh SE Reloaded

[alxlab]

Now that I can understand, with the inductors acting as chokes on the ground. But the SE board only has that single trace from what I can see, which is rather odd, don't you think?

Went down the rabbit hole a bit:

https://resources.pcb.cadence.com/blog/2021-effective-chassis-grounding-techniques
https://www.eevblog.com/forum/beginners/signal-ground-vs-chassis-ground-should-they-be-coupled/
https://www.celectronics.com/pdf/IEEE11-9-05.pdf

So from what I read it could be to ensure that the shield is not left floating if earth ground doesn't exist. That seems reasonable to me. At the same time if earth ground does exist you don't want it to be used as return path for you circuits so I guess that's why it's connected off to the side away from all the digital traces.

 

[Kai Robinson]

As mentioned in our 1:1 chat, it doesn't sound abnormal - compare with the video of the initial headless startup of the board, here:

 

[retr01]

the bong is longer than normal

As I think about the bong being longer, I see delay(s) of the electrons traveling among the circuitry or through one of the sound circuitry/chips. A minor hiccup? The wait is sufficient to cause the bong to be longer.

Could it be one of the components or a solder joint or two? Or do sound waves travel long from the speaker to the human ear due to interference? Could it be the frequency that adjusted somewhat?

How much longer is the bong compared to stock? Timing the bong can help to narrow down the issue. @JDW, can your sound analyzer program time it and compare the bongs via spectrums?

 

[alxlab]

That is true. Good circuit board design usually includes a circuit path that acts as a ground with a piece of metal or to a ground layer of the PCB. I guess that has been around for years.

Can someone shed more light on ground circuitry and whether it is necessary to have a metal chassis?

The Macintosh cases are plastic but they use a conductive paint on the inside to accomplish the same shielding as a metal case. You can test this with a multimeter on continuity mode and touching the grey paint inside a Mac case.

 

[retr01]

https://www.celectronics.com/pdf/IEEE11-9-05.pdf

Excellent material there! The slides clarify very well the grounding methodologies.

So from what I read it could be to ensure that the shield is not left floating if earth ground doesn't exist. That seems reasonable to me. At the same time if earth ground does exist you don't want it to be used as return path for you circuits so I guess that's why it's connected off to the side away from all the digital traces.

Yeah, reduce electronic interference as well as some EMI protection.

Cheers!

 

[retr01]

The Macintosh cases are plastic but they use a conductive paint on the inside to accomplish the same shielding as a metal case. You can test this with a multimeter on continuity mode and touching the grey paint inside a Mac case.

That makes sense. My SE/30 case still has the original conductive coarse coating inside. I noticed some people pop those cases in the dishwasher to clean them. Bad idea? Others say that the layer is not necessary and going bare is fine. I'm afraid I have to disagree.

However, when the CRT and analog board are gone after putting in an LCD screen, the effort needed to ground and provide EMI shielding is less? The LCD has a ground and EMI shielding with the remaining logic board with ground circuitry. New PSU has its ground and EMI shielding. Safe to replace the metal bracket chassis with a 3D-printed one?

Case point, the IIci does not have a metal bracket chassis. But, there is a conductive metal smooth coating inside the plastic case.

Cheers,

 

[Paolo B]

My two cents…
The metal bracket of the SE board is mainly a mean for mechanical assembling. Of course, it has to be grounded, like the whole chassis.
Pathways to ground are redundant by design.
The conductive paint on the case is for electromagnetic shielding, surely not for grounding.

 

[alxlab]

Well the

My two cents…
The metal bracket of the SE board is mainly a mean for mechanical assembling. Of course, it has to be grounded, like the whole chassis.
Pathways to ground are redundant by design.
The conductive paint on the case is for electromagnetic shielding, surely not for grounding.

Hmm I'm not sure if it's just mechanical. They could have used a lot less metal to accomplish the same mechanical strength were the screws fasten the board to the metal frame which in turn would reduce costs. I don't think it would be unreasonable to suggest they were trying to also mitigate the holes in the case's shield (Faraday cage) caused by the holes for the connectors.

 

[retr01]

They could have used a lot less metal to accomplish the same mechanical strength

That!

Cheers,

 

[Paolo B]

They could have used a lot less metal to accomplish the same mechanical strength were the screws fasten the board to the metal frame which in turn would reduce costs.

Maybe so, but a piece of steel that small costs literally nothing in terms of grams of steel used to make the part. Other direct and indirect costs are surely the greatest share of the production costs. On a machine that costed many hundreds of dollars and was sold for thousands of dollars and with a hefty margin, I don’t think anyone went past the iteration 1 of specification settings, design and validation loop for this bracket.
As for the Faraday cage effect, it seems a reasonable design requirement for meeting the regulations. However, the shielding function in the area of the connectors is fulfilled by design by the shroud at the bottom.

 

[retr01]

It was more expensive in the 1980s because Apple had a LOT LESS cash flow and was hemorrhaging dollars in the Macintosh project. So, they cut production costs here and there. Then, Apple still had to sell the Macs for more than the everyday person could afford. Nowadays, much different. Much cheaper and less is needed, especially with the M1 and M2. Far from the internally cramped compact Macs, today's iMacs and MacBooks have much internal space compared to five years ago, especially 30 years ago.

The fascinating thing is that the Apple II series (except the Apple IIc and IIc+) and some Macs such as the IIci did less materials and had less cramping space than other Macs of the day.

Whoops! Back to the topic of SE Reloaded!

Cheers,

 

[JDW]

I am continuing the technical discussion about the split Ground Plane over at the EEVBLOG thread.

 

[JDW]

I left my stock, working SE board (donated to me by Marcus Hesse) at the office., and I am here at home now testing my SE Reloaded board. My SE Reloaded board checks out fine with my TechStep and basically every other test I've conducted, but SCSI Director Pro puzzles me. It throws an Address Error every time I click the "Test" button. That is true of SCSI Director Pro 4.0, regardless of whether I boot from System 6.0.8 or 7.1 (operating systems it is compatible with). It also happens when I try SCSI Director Pro 2.1.7 and boot off the 800K floppy image on my FloppyEMU. The screenshot below is version 2.1.7 booted off my FloppyEMU.



In all cases, the app loads just fine, but the bomb occurs when I click a SCSI drive I want to test and then click the "Test" button within the app.

Those of you with a Mac SE (must have old ROMs and IWM, compatible with 800K disks but not 1.44MB disks -- not the SE FDHD model), have you experienced the same problem?

I really want to get SCSI Director Pro to work because I've used it to graph out BlueSCSI & MacSD performance on my SE/30 machines and Color Classic Mystic, so I'd like to get it to work on my SE too. Nothing I read in the files on Macintosh Garden indicate it is incompatible with the SE.

 

[MacKilRoy]

I left my stock, working SE board (donated to me by Marcus Hesse) at the office., and I am here at home now testing my SE Reloaded board. My SE Reloaded board checks out fine with my TechStep and basically every other test I've conducted, but SCSI Director Pro puzzles me. It throws an Address Error every time I click the "Test" button. That is true of SCSI Director Pro 4.0, regardless of whether I boot from System 6.0.8 or 7.1 (operating systems it is compatible with). It also happens when I try SCSI Director Pro 2.1.7 and boot off the 800K floppy image on my FloppyEMU. The screenshot below is version 2.1.7 booted off my FloppyEMU.

View attachment 6352

In all cases, the app loads just fine, but the bomb occurs when I click a SCSI drive I want to test and then click the "Test" button within the app.

Those of you with a Mac SE (must have old ROMs and IWM, compatible with 800K disks but not 1.44MB disks -- not the SE FDHD model), have you experienced the same problem?

I really want to get SCSI Director Pro to work because I've used it to graph out BlueSCSI & MacSD performance on my SE/30 machines and Color Classic Mystic, so I'd like to get it to work on my SE too. Nothing I read in the files on Macintosh Garden indicate it is incompatible with the SE.

Have you tried any other diagnostics like Apple’s MacTest suite of software?

Apple MacTest Pro (680x0) CD-ROM 691-0590-E 1996 : Apple : Free Download, Borrow, and Streaming : Internet Archive

Apple MacTest Pro (680x0) CD-ROM 691-0590-E 1996

archive.org

 

[JDW]

Have you tried any other diagnostics like Apple’s MacTest suite of software?

Apple MacTest Pro (680x0) CD-ROM 691-0590-E 1996 : Apple : Free Download, Borrow, and Streaming : Internet Archive

Apple MacTest Pro (680x0) CD-ROM 691-0590-E 1996

archive.org

No need for MacTest because, like I said, I used my TechStep to fully diagnose all ports. I did attempt to use MacTest SE earlier today to satisfy my curiosity; however, it cannot complete the logic board tests because it requires a special loopback cable and a special SCSI board which I do not have. But aside from my TechStep testing, I've been using all ports without issue.

I simply left my other SE board at the office so I cannot compare with that right now, and I posted here in hopes of hearing from SE owners who might have tried SCSI Director Pro before. If they too get the same error on an SE with ROMs like I have (800K compatible, not 1.44MB compatible), then I know it's not just me.

UPDATE: I ran Apple Personal Diagnostics. It found nothing wrong.

 

[Kai Robinson]

Do scsi devices behave correctly, as in using a bluescsi?

 

[JDW]

Do scsi devices behave correctly, as in using a bluescsi?

Yes. I have tested it with a BlueSCSI and with a MacSD, using System Picker to switch between System 6, 7.0.1, 7.1, and 7.5.5.

 

[Kai Robinson]

Does macbench run the tests on the disk correctly?

Does FWB hard disk toolkit work?

I'm guessing that the SCSI DMA fakery that's going on with the SE might be at fault... Unless someone can test if it's just an issue with the working SE board and not just the Reloaded.

 

[JDW]

Does macbench run the tests on the disk correctly?

Does FWB hard disk toolkit work?

I'm guessing that the SCSI DMA fakery that's going on with the SE might be at fault... Unless someone can test if it's just an issue with the working SE board and not just the Reloaded.

When I booted into System 7.1 (freshly installed version from 800K disks, compatible with the Mac SE) from my BlueSCSI and then double-click FWB Hard Disk Toolkit 2.0.6, it crashes with the following error...



And when I double-click the FWB SCSI Configure app, I get an "address error." (While booted into System 7.1)

But I don't know if it is compatible with the Mac SE because the Macintosh Garden description makes so such mention...

FWB Toolkits [Hard Disk Toolkit v1.7 + v2.0.6, RAID Toolkit 1.8] - Macintosh Garden

The first download are the 5 installer disks that came with the FWB RAID Toolkit. There is the RAID Toolkit v1.8, FWB Hard Disk Toolkit v1.7 and the FWB Jackhammer driver disk. The second download contains the contents of the FWB Hard Disk Toolkit v2.0.6 that I found on my PPC.

macintoshgarden.org

SCSI Probe 3.5 works fine though. (While booted into System 7.1)

MacBench 3.0 cannot run due to insufficient RAM. (While booted into System 7.1)

Speedometer 4.01 crashes with an "unimplemented trap" error. (While booted into System 7.1) However, Speedometer 3.06 launches and runs to completion without crashing. (Disk Score = 1.512, with a Mac Classic = 1.0)

Norton System Info 3.5.3 finishes its full suit of benchmarks without problem. (While booted into System 7.1)

@Kai Robinson, note that in addition to my TechStep giving the SE Reloaded board a clean bill of health, I ran Apple Personal Diagnostics 1.1.3 and it too showed that all tests passed.

 

[JDW]

I should mention one other thing that is not related to SCSI...

I am able to get very old versions of macOS to run on the SE Reloaded board, including System 0.97 & Finder 1.0. However, I tested the 400K Macintosh 128K Guided Tour floppy just now, and although it boots to the main menu fine, clicking any of the buttons results and what you see in the screenshot here...

Again, I'm at home and my stock SE board is at the office. I am only testing on my SE Reloaded at this time.