Mac color classic troube

Discussion in 'Apple Collectors' started by johntommybob, Jul 2, 2014.

  1. johntommybob macrumors member

    Joined:
    Sep 5, 2006
    #1
    I have a Color Classic I bought back about 1991, and up to last year it had been trouble free, thought little used anymore. I kept it plugged in all the time, but my grand kids unknowingly unplugged it. I didn't go into that guest room for over a year as my wife had an extended illness. When I found out it was unplugged and reconnected it I could not get it to boot up.

    I took it to the certified Apple tech (a young guy) at the local university computer store. I don't think he had ever seen one like it before and became interested in trying to find out what was wrong. I called him today and he said he had got it to start up and could hear the start up chime, but the screen would not come on. He is not getting it to boot by the keyboard, but by some other method.

    Maybe some of you guys have been down this road and could give some advice.

    I am attached to that little mac. It was my first computer. I ran a business with it (retired now), and my daughter used it when she was going through college.

    Thanks,
     
  2. MacTech68 macrumors 68000

    MacTech68

    Joined:
    Mar 16, 2008
    Location:
    Australia, Perth
    #2
    Firstly, I'd be ensuring that he's tried the contrast buttons on the front of the machine to ensure that it's not just the contrast setting that is turned all the way down. (The front panel has volume and contrast setting buttons).

    Secondly, the brightness is controlled by the brightness control panel within the operating system. If the screen is completely dark, this isn't possible, but "zapping the PRAM" should return the brightness setting to a 'default' state.

    With respect to the PRAM, if the machine has been unplugged from the AC mains or switched off at the rear, the PRAM battery will most likely be flat. The standard procedure is to measure it whilst still in place, and if it measures less than 3.0 volts, replace it.

    However, IIRC, some Color Classics have a 3.6v half AA sized lithium battery, and some had a 4.5v cube shaped Alkaline battery.

    Also, if the battery has gone flat, some PRAM settings may have become corrupted. It may be worthwhile removing the battery from the motherboard and shorting the empty battery terminals on the motherboard overnight, then remove that shorting device the next day, and seeing if it will power back up - this can be done WITHOUT a battery fitted.

    I'm intrigued by the need to power the machine up by a method other than the keyboard. Of course, this can be done by momentarily shorting a certain pin on the ADB port (4pin keyboard/mouse port) to ground. The ADB cables can have their pins bent if the plug is inserted at an angle, and the Apple ADB keyboards with a removable cable can develop cracked solder joints on the ADB sockets (there is one at either side of the keyboard).

    If it is powering up, then the standby and main power supplies (both on one board) are basically working. There are other possibilities that could cause a black screen (cracked solder joints on the CRT PCB is just one). The CRT PCB is inside a sliver metal box that plugs onto the back of the picture tube.

    Hope some of that helps.
     
  3. havokalien macrumors 6502a

    havokalien

    Joined:
    Apr 27, 2006
    Location:
    Kelso, Wa
    #3
    color classic motherboard

    The capacitors on the motherboard have or are failing and need to be replaced. Due to age they have just gone bad. The unplugging could have spiked it but just FYI it was past due for sure.

    I have two of them and both motherboards needed new capacitors. They have been replaced and are good to go until something else breaks.

    the fact it doesn't come on by the keyboard is a tell tale sign.
     
  4. MacTech68 macrumors 68000

    MacTech68

    Joined:
    Mar 16, 2008
    Location:
    Australia, Perth
    #4
    Yup, I'll vote for that too. I should have known. :(
     

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