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Dipper184

Macintosh color classic won't power on

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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?

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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.

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1 hour ago, 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.

Thank you very much! I just washed the logic board with alcohol and put it into mac and mac turned on.

Edited by Dipper184

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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.

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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. 

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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.

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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?

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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.

Edited by Bolle

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11 minutes ago, 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.

My board doesn’t have a CUDA reset switch. Anyway to reset it?

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18 hours ago, 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.

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.

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19 minutes ago, 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.

What happens when PRAM battery isn't in and powers on? Nothing at all? 

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On 10/11/2018 at 10:10 AM, 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.

 

On 10/11/2018 at 11:45 AM, Dipper184 said:

Thank you very much! I just washed the logic board with alcohol and put it into mac and mac turned on.

 

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

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3 minutes ago, dochilli said:

Did you try to power the CC up without the mainboard and pushing the mainboard into the slot then? Sometimes it works.

 

Tried before. Doesn't work. The fan spins without board. I'll try again later

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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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Just now, Bolle said:

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)

Even the fan spins the analog board could be faulty?

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Yes. It might be fine with nearly no load attached (i.e. no logicboard installed) but once you have the logicboard in there it will draw a lot more power (especially on the 5V line)

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