IIsi: Minimum needed to troubleshoot a motherboard

[YarMac]

The posts here are very helpful, thank you for all the topics over the past few years.

In the process of restoring my //si from 1990. My main question is:
What is the minimum needed to test the motherboard?
The objective is to get an indication that refurbishing the board was successful with minimum connections.

1. Does the PRAM battery need to be installed?
Found answers for other Mac II models but not specifically the IIsi.

2. Remove all SIMMs?
Assuming all SIMMs can be out, the built-in RAM should be enough.

3. Floppy or HD?
I recall that without a drive it should boot to a question mark screen, but will it still audibly chime?

4. Video?
With video, success should be clear because the screen will show happy mac, sad mac, etc.
Without video, that leaves only audio for verification.

5. Keyboard?
The lights on the Apple Extended Keyboard II should light up and at some point of success caps lock can toggle its light - does that work before the OS starts up?

6. Speaker?
Without video, this is really the only indicator of success, with the proper chime. Failure is indicated by click click click click.

Some notes and background:

• PSU recap failed so for now I'm using an ATX supply with a modified connector (including 5v trickle).
• There are many things to get working (BlueSCSI, PSU, video, etc.) and I want the motherboard to work before investing in the other items.
• I don't want to spin up the floppy or HD yet and don't have my BlueSCSI working yet.
• Griffin Mac-PnP is used for video but I've never confirmed that this used unit works or that the Dell LCD will display its output. So far the monitor won't come out of sleep in any test.

 

[Garrett B]

If it were me, I'd isolate everything to the logic board (no RAM SIMMs) and power supply only. You don't need a battery. Start with those items and headphones plugged into the headphone jack. If your onboard RAM is good, you'll hear a chime. If not, it'll be death chimes (in which case you wouldn't get video output). If it chimes with headphones, next step is to connect a monitor. You may uncover additional issues here involving the RBV circuitry. Schematics are your friend in every step of the way! I've never had a IIsi where a simple recap was the fix-all. Every one has required trace repair unfortunately. Good luck!

 

[joshc]

1. Does the PRAM battery need to be installed?

No, it does not need to be installed on the IIsi for troubleshooting or normal operation.

I recall that without a drive it should boot to a question mark screen, but will it still audibly chime?

You don't need floppy or HD connected to test it. It should chime without them.

6. Speaker?

The speaker can be faulty on these, the speaker contacts in particular are troublesome. Test with the headphone socket instead.

2. Remove all SIMMs?

The IIsi has onboard RAM and ROMs so you should be able to test it without any SIMMs installed.

 

[Phipli]

B

The posts here are very helpful, thank you for all the topics over the past few years.

In the process of restoring my //si from 1990. My main question is:
What is the minimum needed to test the motherboard?

This is me testing a IIsi a while back - I'm using an external speaker with the sound out minijack because someone just sent me the board. I'm using a Centris 650 PSU with a home made extension. It has an aftermarket ROM so the chime is weird.

View attachment VID_20221108_162258.mp4

The objective is to get an indication that refurbishing the board was successful with minimum connections.

1. Does the PRAM battery need to be installed?
Found answers for other Mac II models but not specifically the IIsi.

No battery needed.

2. Remove all SIMMs?
Assuming all SIMMs can be out, the built-in RAM should be enough.

No RAM SIMMs needed to chime. But that doesn't leave much to boot an OS - I think it is only 1MB, so you'll need a System like 6.0.8.

3. Floppy or HD?
I recall that without a drive it should boot to a question mark screen, but will it still audibly chime?

Neither required to get to the questionmark. Its slow showing the question mark with no floppy drive. Be patient.

4. Video?
With video, success should be clear because the screen will show happy mac, sad mac, etc.
Without video, that leaves only audio for verification.

For the first test to see if it chimes, no video needed. I'd then plug an Apple monitor in. Apple to remove the doubt of having the wrong adapter settings.

5. Keyboard?
The lights on the Apple Extended Keyboard II should light up and at some point of success caps lock can toggle its light - does that work before the OS starts up?

It does yes. But if ADB isn't working, you likely won't get to the flashing questionmark.

6. Speaker?
Without video, this is really the only indicator of success, with the proper chime. Failure is indicated by click click click click.

I use headphones or an external battery powered speaker.

Some notes and background:

• PSU recap failed so for now I'm using an ATX supply with a modified connector (including 5v trickle).

Don't forget the fan starting is another clue that things are at least partly working. You could use an ATX adapter to test with an ATX supply.

• There are many things to get working (BlueSCSI, PSU, video, etc.) and I want the motherboard to work before investing in the other items.
• I don't want to spin up the floppy or HD yet and don't have my BlueSCSI working yet.
• Griffin Mac-PnP is used for video but I've never confirmed that this used unit works or that the Dell LCD will display its output. So far the monitor won't come out of sleep in any test.

Notes :

I wouldn't worry about testing all subsystems. The ROM Test (make sure you use a stock ROM, not an aftermarket one - they skip tests) will flag most things, and it is easiest or even only possible to test ADB, serial, SCSI, floppy etc with devices connected.

 

[YarMac]

Thank you all for the fast responses. The headphone/external speaker idea was great and obvious in hindsight. That removes the one annoying detail of needing to reinstall the motherboard in the case after each interim repair.
Other posts here, including this recent one from Sunday have the next details for continuing the troubleshooting. I've gone through and touched up the pins on UE5, UF5, UG5, and UH5. Found three pins detached total on those four chips. I'll keep chugging through...