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Mac II won’t boot after recap.
- Thread starter crazyben
- Start date
Juror22
Well-known member
Here are a couple items to check, from when I looked over the picture. Not sure if they are anything or not, just ideas for things to check.
- There seems to be a scratch across the vias where the negative battery terminal attaches (near B2). You might check where the traces lead for continuity (if it is a scratch and not just an issue with the photo)
- Where the leads for C5, C140, C122 connect to the board, could maybe use more solder on the connection (it might be fine, you could check continuity, but they look 'skimpy' from the top)
- Y1 looks a bit askew, (maybe make sure that the one lead isn't damaged)
- Recheck the power at the battery connections to the board and be sure you have the right amount of power coming from each battery.
- There seems to be a scratch across the vias where the negative battery terminal attaches (near B2). You might check where the traces lead for continuity (if it is a scratch and not just an issue with the photo)
- Where the leads for C5, C140, C122 connect to the board, could maybe use more solder on the connection (it might be fine, you could check continuity, but they look 'skimpy' from the top)
- Y1 looks a bit askew, (maybe make sure that the one lead isn't damaged)
- Recheck the power at the battery connections to the board and be sure you have the right amount of power coming from each battery.
Near b2 just on phone. I will put some more solder on the caps you mention. Y1 is not damaged.
Someone suggest I do power jump and that did it. Mac ii boots up and working like before. Now I have to do that every time I have to boot up. Is there a permanent fix for that?
Someone suggest I do power jump and that did it. Mac ii boots up and working like before. Now I have to do that every time I have to boot up. Is there a permanent fix for that?
treellama
Well-known member
This helped me get my IIx to soft power on: https://www.downtowndougbrown.com/2015/03/explanation-of-the-macintosh-iiiix-power-onoff-circuit/
I read that before and I must admit it is way too technical for me. I did not have any leaky capacitors. It was all axial capacitors and I replaced it just to be in safe side. I will attempt this once I am more versed on technical stuff. But for now I will have to do the jump method.
jmacz
Well-known member
Use a multimeter on pin 15 on the PSU connection to the motherboard and ground (one of the pins 7 through 12). Set the multimeter to measure DC voltage. It should read zero volts when your Mac II is off. Now watch the multimeter display and press the power button on the motherboard. You should see it read 6+ volts and then the power supply should turn on. If you don’t see it read 6+ volts, you have a problem and that’s why you need to jump it.
If you don’t see the volts on pin 15, you either have one or two dead or low PRAM batteries, or those PRAM battery holders you are using have a bad connection to the motherboard, or the power switch is broken, or you have a broken trace near those batteries or in the corner of the board near the power switch (and also the area near the power switch between the rear ports and memory modules).
The power switch causes voltage from the two batteries to get to pin 15 on the psu connector which then signals the psu to turn on, which then powers your Mac. The lack of voltage getting to pin 15 is most likely the source of your problem.
If you don’t see the volts on pin 15, you either have one or two dead or low PRAM batteries, or those PRAM battery holders you are using have a bad connection to the motherboard, or the power switch is broken, or you have a broken trace near those batteries or in the corner of the board near the power switch (and also the area near the power switch between the rear ports and memory modules).
The power switch causes voltage from the two batteries to get to pin 15 on the psu connector which then signals the psu to turn on, which then powers your Mac. The lack of voltage getting to pin 15 is most likely the source of your problem.
I desoldered the pram and solder it again and now the power button is working. When I test the voltage is 12 and 15. I get less than 6 volts. (4.49 to be exact) does that mean the pram batteries are dying out? If that’s the case I am okay with that since it’s an easy fix.
jmacz
Well-known member
Ok great to hear that it's working again for you.
So both of those PRAM batteries should be producing 3 to 3.6V each. But perhaps I'm wrong that the full voltage is sent to that PFW pin 15. I thought it was 6V+ that I saw but it's been about 3 months or so since I was debugging my own Mac II so I could be remembering wrong.
Check the voltage on each of those PRAM batteries and if each is in spec for their size (ie. 3V+ each depending on the type of battery it is), then you should be fine I think. As long as it's enough to tickle the PSU to start up, I think you should be fine.
So both of those PRAM batteries should be producing 3 to 3.6V each. But perhaps I'm wrong that the full voltage is sent to that PFW pin 15. I thought it was 6V+ that I saw but it's been about 3 months or so since I was debugging my own Mac II so I could be remembering wrong.
Check the voltage on each of those PRAM batteries and if each is in spec for their size (ie. 3V+ each depending on the type of battery it is), then you should be fine I think. As long as it's enough to tickle the PSU to start up, I think you should be fine.
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