The Macintosh revenge

[Papalapa]

No no, it is not the title of a movie, today I turned on the Macintosh SE 1/20 and the Macintosh LC II and neither of them worked

The day before yesterday it was the the PC power supply (it is already replaced and working), the dishwasher machine (damaged motor) and today to the two Macs. I have come to think of a voltage surge but it is almost impossible, in the area where I live never happened but so much concentration of electronic breakdowns in four days it's annoying or maybe simple bad luck....

Anyway, the Macintosh SE 1/20 is already repaired, it was a false contact in two SIM modules, one that has two broken retention tabs broken and I fixed them in the past with hot glue and the other SIM module that has the contacts quite damaged. Contact cleaner, double zero sandpaper, eraser rubber and alcohol and I have only managed to leave them as the photo shows so I don't know how long it will work. At least for now it works.

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KbtzNj8.jpg

What really worries me is the Macintosh LC II. When turned on, nothing appears on the screen, there's no "chord" sound and although the hard drive tries to boot there it stays. It is also not possible to boot from floppy because the drive does not load during boot. The fan of the box does turn, is the only part that works.

I have measured the power supply output voltages and all of them are correct. I have removed the network card, disconnected the hard disk, the disk drive and even the memory SIMs and the problem remains, It only turns the fan but does not start, so I think that most probablt the malfunciton is located at the motherboard. Visually there are not damaged components and leaving the Mac turned on for 5 minutes, only the microprocessor is a little warm, but not more than normal.

The Apple service manual arrived at this point proposes to replace the motherboard, but now it is not easy to find one of these in conditions in Europe...

Can I do some more test to try to find out what is wrong or is better to forget it and start to look for a second-hand motherboard?

[chscag]

I would think you've already done what trouble shooting that can be done. Looks like it's time to start swapping parts. I worked for many years as an electronic tech on sophisticated commercial equipment and also consumer grade stuff. The procedures are pretty much the same in that when you've checked everything out according to good techniques, the only thing left that you can do is swap parts.

I wish you luck in finding a motherboard for the LC II. If you were here in the states, you probably could find one by buying another non working LC II, or on eBay.

Let us know how it went.

[dtravis7]

I would think you've already done what trouble shooting that can be done. Looks like it's time to start swapping parts. I worked for many years as an electronic tech on sophisticated commercial equipment and also consumer grade stuff. The procedures are pretty much the same in that when you've checked everything out according to good techniques, the only thing left that you can do is swap parts.

I wish you luck in finding a motherboard for the LC II. If you were here in the states, you probably could find one by buying another non working LC II, or on eBay.

Let us know how it went.

Not sure where it is since the move in with family but I own a working LCII. I will check and see if I can find a board for the OP or another cheap but working LCII.

[pm-r]

When were the Macs last used??

But it seems that the SE is now operational, but I wonder what the state of the LC's PRAM battery would be as I seem to recall that a dead PRAM battery could prevent those and other models from booting.

If it hasn't been used for quite a while, try leaving it plugged in at least overnight and then try again the next day and see if it might boot. I believe there may be a slight charge applied to the PRAM battery when it is left plugged in, and it just might be enough to get it booted.


- Patrick
======

[dtravis7]

When were the Macs last used??

But it seems that the SE is now operational, but I wonder what the state of the LC's PRAM battery would be as I seem to recall that a dead PRAM battery could prevent those and other models from booting.

If it hasn't been used for quite a while, try leaving it plugged in at least overnight and then try again the next day and see if it might boot. I believe there may be a slight charge applied to the PRAM battery when it is left plugged in, and it just might be enough to get it booted.


- Patrick
======

Bingo! Thanks Patrick. You are 100% right. It's been so long since I messed with the old Macs I forgot that one. Bad PRAM battery on a lot of those will result in it doing nothing.

Worth a try for sure.

[chscag]

If my memory is correct, member "Papalapa" replaced the PRAM battery the last time he posted about the LC II. Don't know about the SE though.

[Papalapa]

Thanks to everybody for the responses, they were very helpfully for me.

chscag is right, I replaced the PRAM battery one year ago and yesterday also measured the voltage with the multimeter and the value was 3,62 volts so, it seems to be correct. LC II and SE were not turned on since 3 months ago because my other "pets" (ZX81, Spectrum, Commodore 64 and Amstrad 464) required my time for refurbishing matters, that why I said that most probably it was a revenge of my Macs. Hopefully G4 and G5 are not angry at the moment

[Papalapa]

When were the Macs last used??

But it seems that the SE is now operational, but I wonder what the state of the LC's PRAM battery would be as I seem to recall that a dead PRAM battery could prevent those and other models from booting.

If it hasn't been used for quite a while, try leaving it plugged in at least overnight and then try again the next day and see if it might boot. I believe there may be a slight charge applied to the PRAM battery when it is left plugged in, and it just might be enough to get it booted.


- Patrick
======

Hi Patrick, do you mean the left the LC II plugged to the mains with the power switch in OFF position? Is there some voltage flow from the internal power supply to the motherboard in this way?

Anyway, I'll try, thank you!

[pm-r]

Hi Patrick, do you mean the left the LC II plugged to the mains with the power switch in OFF position? Is there some voltage flow from the internal power supply to the motherboard in this way?

Anyway, I'll try, thank you!

Yes, plugged into the mains with the LC's power switch in OFF position.

And yes, according to a Mac Tech who told me years ago a lot of the early Mac models had some sort of small trickle voltage to help maintain the PRAM battery voltage.

One of the other problems the early Mac suffered from with a non-boot situation (especially the Classic models) was due to stiction that prevented the hard drive from spinning. But a good sharp rap with a rubber mallet on the side of the Mac would usually fix that problem, at least to get the hard drive spinning.

Good luck.


- Patrick
======

[Papalapa]

Yes, plugged into the mains with the LC's power switch in OFF position.

And yes, according to a Mac Tech who told me years ago a lot of the early Mac models had some sort of small trickle voltage to help maintain the PRAM battery voltage.

One of the other problems the early Mac suffered from with a non-boot situation (especially the Classic models) was due to stiction that prevented the hard drive from spinning. But a good sharp rap with a rubber mallet on the side of the Mac would usually fix that problem, at least to get the hard drive spinning.

Good luck.


- Patrick
======

I have to say that you're absolutely great!

I followed your advice and this morning the LC II turned on normally. I have been shocked when I pressed the power button and I heard the chord from the LC II. Even, I even was thinking to drop the motherboad to the bin because I was sure that it was defective...

Due to this three days ago I started to look for another motherboard for the LC II and I found a Performa 460 without accesories at really good price. Obviously as a good retrocomputer fan I bought the Performa and now I have both, LC II and Performa 460. As they have to share monitor and keyboard I'll try to find a switcher like the ones for VGA monitors because I have no more space for another monitor on the table. In this way I'll avoid to have to connect and disconnect each time I want to use the LC II or the Performa.

Here's a picture of the final assembly. Thanks again Patrick.



.

[dtravis7]

Great job patrick.
Papalapa Glad that worked and your LCII is working again. Somewhere I have/had a Performa like that.

[pm-r]

I have to say that you're absolutely great!

Thank you for the great compliment and it's nice to hear of an old Mac still operational. I'm glad to hear some old Mac tricks can still work.

A Mac LC was our first real computer, well actually our second when the older Adam computer my eldest son gave to our youngest son started to do goofy things and basically not work properly.

It was amazing what we did with that machine and I started to learn how to become a Mac nut.



- Patrick
======

[Papalapa]

Solved...