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Macintosh color classic won't power on

Dipper184

Dipper184

6502
I bought the color classic, previous owner said that it's working but when I connected everything and pressed the soft power button on ADB keyboard, nothing happened (the switch on back was turned on). I found on the internet that I should let it attached to the power for a day, it didn't help. I pulled out the logic board and turned the switch at the back on and I heard fan and hard drive spinning.

Any ideas how to fix it?

 
If the Logic Board has not seen new capacitors, probably won't work.

try to wash the board first, but new caps are the next step to go.

Logic board issue for sure.

 
bibilit said:
If the Logic Board has not seen new capacitors, probably won't work.

try to wash the board first, but new caps are the next step to go.

Logic board issue for sure.
Click to expand...
Thank you very much! I just washed the logic board with alcohol and put it into mac and mac turned on.

 
Last edited by a moderator:
You will need to replace the capacitors on the logic board. If cleaning the whole board with alcohol is required the caps have leaked. They will soon, if not already, be out of specification.

The Color Classic is very easy to recap.

 
My CCs won't boot without PRAM batteries. Do you have one installed?  I can also get them to boot by pushing the red CUDA button on the motherboard when they are plugged in (with a pencil or something non conductive with the back panel off) before pressing keyboard power on.  Not all CCs have the CUDA button. 

 
color classic work fine without pram batteries, if yours have issues like that redo the capacitors and hurry as traces could be rotting away as you wait.

 
I have the same issue. Motherboard was recapped. Initially it worked fine. Until a day later I can’t power it on. Shows 6 flashes of LED when pressed power key on KB. Analog board is fine as previously it powers up. Also fan turn on when motherboard is removed.

what could be the problem?

 
The CUDA on the CC logicboard seems to be really sensitive to corrosion/cap goo.

Most CCs with power up issues I had on my bench were fixed by removing the CUDA, cleaning the chip and the pads really extensively and soldering it back on.

Also a few vias/traces around the CUDA leading to pullup/pulldown resistors tend to get eaten away by cap goo leaving inputs floating on the CUDA which also results in weird behavior.

If a CC is not powering up without a PRAM battery or needs constant CUDA resets there is an issue with the CUDA.

 
Last edited by a moderator:
Bolle said:
The CUDA on the CC logicboard seems to be really sensitive to corrosion/cap goo.

Most CCs with power up issues I had on my bench were fixed by removing the CUDA, cleaning the chip and the pads really extensively and soldering it back on.

Also a few vias/traces around the CUDA leading to pullup/pulldown resistors tend to get eaten away by cap goo leaving inputs floating on the CUDA which also results in weird behavior.

If a CC is not powering up without a PRAM battery or needs constant CUDA resets there is an issue with the CUDA.
Click to expand...
My board doesn’t have a CUDA reset switch. Anyway to reset it?

 
Bolle said:
The CUDA on the CC logicboard seems to be really sensitive to corrosion/cap goo.

Most CCs with power up issues I had on my bench were fixed by removing the CUDA, cleaning the chip and the pads really extensively and soldering it back on.

Also a few vias/traces around the CUDA leading to pullup/pulldown resistors tend to get eaten away by cap goo leaving inputs floating on the CUDA which also results in weird behavior.

If a CC is not powering up without a PRAM battery or needs constant CUDA resets there is an issue with the CUDA.
Click to expand...
Well thanks for that.  I had just assumed that the CC was like some of the LCs that need PRAM batteries to boot (although I guess they aren't soft power so I should have realized the issue wasn't common).  Now I need to go back, rewash my logic boards and check cuda traces and related hardware.

 
superjer2000 said:
Well thanks for that.  I had just assumed that the CC was like some of the LCs that need PRAM batteries to boot (although I guess they aren't soft power so I should have realized the issue wasn't common).  Now I need to go back, rewash my logic boards and check cuda traces and related hardware.
Click to expand...
What happens when PRAM battery isn't in and powers on? Nothing at all? 

 
bibilit said:
If the Logic Board has not seen new capacitors, probably won't work.

try to wash the board first, but new caps are the next step to go.

Logic board issue for sure.
Click to expand...


Dipper184 said:
Thank you very much! I just washed the logic board with alcohol and put it into mac and mac turned on.
Click to expand...


Recently had a Color Classic II board stop working on me... same symptom, no boot and no life even though the Mac boots up with another board, so I know that the analog board is fine. Followed the advice on cleaning board with 90% 2-propanol (isopropyl), specifically around the capacitors and component-heavy areas, installed, and it powered right on! You guys saved me a lot of headache! My eternal thanks

 
I tried spraying cleaner for computer board. Added PRAM battery and power on. Still the same, it doesn't power up. Does the number of flash on the LED tells any fault?

 
The LED is not supposed to flash at all. Flashing could indicate power supply failure.

CC analog boards are prone to cap failure as well and need new caps most of the time (at least in the logic board power supply section)

 
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