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!
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.
mac_se_logic.jpg
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!
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
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.
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
Indeed a good solution for a dead HDD, you can tuck it inside the case and happy days, I agree. Thanks for mentioning!
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.
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!
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.
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.
I've published part 2 of the repair video, let me know what you think! :)
https://www.youtube.com/watch?v=siR-XEheM90