Macintosh SE restoration

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Macintosh SE restoration

As you might have noticed I am restoring an SE! Sorry for the many threads, I just didn't want to hack the existing ones with OT questions.

 

I have a couple more questions for this system.

1. Battery. I removed the Varta battery (which surprisingly has still 2.9V in it!) and found that my CR2032 battery holders really don't fit elegantly. I'd like a better solution. Before re-inventing the wheel I was wondering if someone has come up with a good solution. Either a better holder or maybe a small PCB interposer to allow a standard holder in place. Maybe - if height allows - to be installed vertically? If not, I'll try to design one and share here!

 

2. The computer fails to boot every now and then. I turn it on, I have the "fine diagonal lines background". But after around 17 seconds I normally hear a "click" from the speaker and the computer finally boots. Sometimes that never happens and the computer stays with that background forever. If I reset using the button, it works fine.

It seemed it was happening when cold but today it happened after being off for a couple of minutes. Voltages seem ok, maybe -12V is on the low side (-11.6V) but I have a feeling it's not such an important voltage.

 

I can check the reset line but I was wondering if anybody had any ideas - maybe it's a known issue with this machine!

 

Thank you!

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etc

Probably not the best idea to use a vertical CR2032. The clearance is quite limited as a result of the sheet metal screening above the board in situ.

Some horizontal thru-hole holders seem to be a surprisingly good fit. I've attached a picture of one I found from an australian repairer.

17 seconds pause with a gray screen seems too long, unless the hard disk takes that long to become ready.
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You're right about the

You're right about the clearance, I checked and indeed it cannot be vertical.

I admit a interposer would not make such a huge difference. Maybe I'll just find some better holders!

 

I am not very much skilled with the Macintosh. The Miniscribe seems to be a bit old - sometimes it makes "banging heads" noise when power up. However I hear the drive seeking and then doing nothing - until I hear that click and the computer actually starts up. 

I have a Floppy emu coming so I should be able to remove many other variables. Could it be the HDD preventing the boot process? Wouldn't I get the floppy icon on screen? 

Thanks!

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You may want to also look at

You may want to also look at the BlueSCSI hard disk emulator for the SE.   It is a small reasonably priced device that emulates hard drives using an SD card.  There is an internal version and a DB25 external version.   There are several authorized sellers for these.  I am one of them and sell them on eBay, but others also have them.   See this site:   https://scsi.blue/

 

Jay 

 

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Thanks Jay! I might be

Thanks Jay!

 

I might be mistaken but I thought the Floppy emu could also emulate an HDD? Still, for the price, it might be nice to have a "fixed" HDD in those macintosh. Thanks for mentioning.

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Hi Tony,   They can, but they

Hi Tony,  

 

They can, but they are external and work over the floppy drive port.   Bluescsi connects to the SCSI port and is a little faster.   

 

J

 

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Indeed a good solution for a

Indeed a good solution for a dead HDD, you can tuck it inside the case and happy days, I agree. Thanks for mentioning!

 

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To update: the issue was with

To update: the issue was with the ADB chip. It was preventing the system from booting (also preventing mouse and keyboard from working). Once replaced, all was good.

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I made a repair video of this

I made a repair video of this Macintosh SE, I hope it's ok to link it here:

 

https://www.youtube.com/watch?v=e0DJYUwJMFw

 

Let me know what you think!

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Nice video!Note that the

Nice video!

Note that the flyback transformer (LOPT) on the SE has a bleeder resistor, so you usually won't hear any snap when discharging the CRT's second anode. Earlier models had no bleeder and could remain charged for days. It's still a good practice to discharge the tube if you need to remove the anode cable.

As far as danger to life is concerned, I would have put the warning on the segment with the PSU under test with its cover removed. The primary side smoothing cap can supply a lot more heart-stopping current compared to a 9" CRT. I know you don't touch anything near it on the video, but it's a missed opportunity to put safety risks in perspective.

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You are totally right - I

You are totally right - I forgot :) I am totally aware of the dangers but it's Youtube, I should have added a warning there too. 

 

I suspected there was a bleeder but as you say, better safe than sorry! Thanks for mentioning.

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I've published part 2 of the

I've published part 2 of the repair video, let me know what you think! :)

 

https://www.youtube.com/watch?v=siR-XEheM90

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