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Mac Color Classic - No Video
Posted by: Private19872 on 2018-01-30 13:07:35
Hi everyone, I'm new to the forums, but I was wondering if anyone could me troubleshoot my Mac Color Classic (stock, no upgrades like Mystic or Takky).

I opened the computer and replaced the original 80MB HDD with a 2.1GB disk. Before, the screen worked and it showed the blinking disk icon, but now even though the computer turns on and makes the startup chime, the screen is entirely dark. I wouldn't be surprised if this was a cable I knocked loose or forgot to reconnect when I was removing the analogue board, but so far, I haven't been able to find anything out of place.

Here's what I know:

  • The screen still builds up a charge on the outside, which leads me to believe that the issue lies with the electron gun towards the back.
  • The computer sounds like it's booting fine, and I think I can hear the HDD being accessed.
  • I couldn't find any unconnected cables after checking three times. All the wires leading to the video board appear to still be firmly attached to the analogue board.
  • The metal shielding covering the edge connector in the front corner of the analogue board is missing, though the computer appears to have worked fine without it.
  • There's electrical continuity with the ground wire from the video board all the way to the ground pin on the cord.


I was about to try removing the video board from the CRT to have a look, but I figured I'd ask here first before I make any more problems for myself. Thanks in advance for any suggestions.
Posted by: just.in.time on 2018-01-30 14:52:24
Is the logic board and analog board still seated all the way in their respective slots?

have you tried a PRAM reset?

to do so, hold Apple-option-p-r right after you hit the power key. Keep holding until you hear the startup chime 5 times (supposedly just 3 will work, but I like to be sure).
Posted by: Private19872 on 2018-01-30 19:07:25
I'm pretty sure the boards are seated well given that the machine is booting, though to be safe, I did air-dust each of them.

No luck with the PRAM reset. I held down the key combination, but at bootup I would only hear the startup chime once like the computer did before. This might be because my mac doesn't support soft-boot from the keyboard. The previous owner said something to the extent of, "the chip that controls that was broken," and just added a little push button on the back wired directly into the logic board. Then again, I may just be doing it wrong...
Posted by: Private19872 on 2018-01-31 12:04:51
Sorry for the bump, but I did manage (I think) to reset the PRAM. I pulled the battery from the logic board and reinserted it. Unfortunately, the issue doesn't seem to be in the PRAM.
Posted by: just.in.time on 2018-02-02 22:45:23
If you bumped the neck of the CRT, you may have killed it. It doesn’t take much sideways force to snap the neck. Hopefully this is not the case because that CRT tube isnt the easiest to find alone.

have you tried putting back in the original 80mb drive to see if you could get back to the flashing question mark?

also, have you tried pushing the contrast up button on the front while it is running?
Posted by: Private19872 on 2018-02-11 18:54:25
Problem solved, it was a loose plug to the CRT I didn't see because it was under metal shielding. Everything's good now, but it looks like the System 7 installer (System 7.1 with the 401 Enabler) doesn't recognize the new drive. I'm not surprised. It was cheap and untested, so it could very well just be defective. I'll probably just use the original drive for now, but anyways, I'm glad to have my Mac working again.
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