Hi all,

Is there anyone here who knows anything about Macintosh Classic all-in-one computers? I found one at the dump today, but it isn't working (and I am unsure why).

If anyone here has any knowledge of the issue, i'd be most grateful to hear from you.

Note - There are three pins on the memory card, with a two-pin bridge. The image changes when it's set to 'SIMM NOT INSTALLED' and 'SIMM INSTALLED'. It has darker parts when on the 'Installed' setting, and is lighter whenon the 'Not installed' setting.

Chris.

Bad memory maybe? Or the PRAM battery might be dying

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"I'd rather have a CRT than nothing" - me
"people just throw working CRTs out, it is NOT FUNNY!" -me

I'd say at that age the battery on the motherboard would be a definite candidate for replacement. On older computers they were a pack of three or four cells bound with shrinkwrap and soldered directly to the motherboard.

SIMM is just the form factor for older memory cards. Usually no larger than 4MB. Try pulling these out of their sockets and reinserting.

Even though I once owned an iMac I am not really familiar with the Apple boot-up routine. On an IBM-compatible machine (yeah, old terminology for a PC) if the memory can't be counted during the self-test then the BIOS will either not hand over to the operating system or errors will be reported on screen. If the processor is faulty or not inserted correctly then the screen just stays blank.

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A valve a day keeps the transistor away...

Thank you for uploading those photos Brad!

I'll try and order in another PRAM battery, so thankfully there is a Mac computer shop in Port Macquarie. Brad, I've removed and re-inserted the memory chips several times.

Chris

You'll probably find Apple/Mac collectors sites a better source of info, such as:

http://forums.macrumors.com/forumdisplay.php?f=6.

I know absolutely nothing about Macs, but it looks more like a video problem. If it was an IBM I'd check for a pin pushed back in the VGA cable. Don't know if a MAC has something similar...

Warren

The waviness of the display makes me think that the electrolytic capacitors in the monitor or the power supply may need to be replaced. If the waviness seems to crawl up or down the screen (that being the difference between the display's vertical deflection and the powerline frequency).

I have restored several of these old Macs and the symptoms are almost certainly due to electrolytic capacitors on the "analogue board" - the vertical one that holds the PSU and the circuits to drive the CRT. Schematics are hard to find, as Apple never released them to the public, but they do exist and can be found.

I'm sending you the official Developer Notes by email - they include most pinouts and a functional description of the machine.

The forum that specialises in this generation of Macs is 68kMLA.org/forums. There are years of discussion on exactly these topics. You might need to sign up to the forum in order to ask a question, but 99% of the time you will find the info you need in the threads already there.

It is pretty much standard practice with this generation of Macs to replace ALL the electrolytic capacitors on the motherboard (Apple calls it a "logic board") and probably the main ones on the analogue board. The ones that haven't failed yet can be expected to fail soon. You will see up to date threads on caps replacement for the Classic and other models.

You'll see threads on battery replacement as well. Sometimes the battery is off the board in a separate compartment - depending on the model.

The good news is that if it is showing that pattern, there is a good chance that you will be able to get it going. Do you hear the hard drive spin up, and does the display change at all during the boot process? One trick is to boot it once to heat up the CRT, then switch it off and boot again while the tube is still warm. That way you can catch any movement in the display.

There should be 4 memory slots and they need to be filled with matched pairs of SIMMS. The jumper may be to set how many SIMMS you are using. I recommend you check the model number on the label on the back (it will start with M...) and download the Apple service guide from Apple or one of the other sources that you will find with a google search.

You are very lucky to have found one at the tip. They fetch quite a lot in good condition, and are often sold only to local buyers because sellers can't be bothered posting them.

Maven