A signal with two of these indicates that it went to 2 other places in the schematic. 19D3 = page 19, Row D, column 3, and so it goes. Critical means that that component placement in the logic board and replacement must be exact.
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SMC Issue on MBP 13 - Hardware Troubleshooting Guide
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A signal with two of these indicates that it went to 2 other places in the schematic. 19D3 = page 19, Row D, column 3, and so it goes. Critical means that that component placement in the logic board and replacement must be exact.
"Open" and "short" are idealisations invented by the impatient. They don't have a precise definition and are best thought of as outcomes of a test procedure that varies from one situation to another.
Let's start with "short". It means "a huge leak in the circuit we're testing". Now all we need is to define "huge". Let's say, you're testing a 5kV power circuit for a He-Ne laser, and your ohmmeter reads 1 megaohm. That's a short, because your power supply will lose 25W through that leak, provided it can cope with it. It probably can't. For the opposite extreme, consider the massive lead connecting one of your car's battery terminals to the body. You test it with your ohmmeter and it reads 0.01 ohm; (most meters will show it as 0). Is it a short circuit? It would be, from the battery's point of view, if you connected it across the battery's terminals. That would make for a huge leak. But in some cars, the voltage drop across the ground lead is used to sense the battery current, so it is not that short from the sensor's point of view.
In a typical logical circuit, if you measure resistance to ground or to the power bus, you will need to worry about a possible short if your meter shows less than 1k for a TTL circuit, and less than 10k for a CMOS circuit (Note: these are just rough rules of thumb. It can be 10k and 1M, respectively). Also, it will depend on whether you're testing a live circuit or not, and in what direction. I would be more suspicious of a short if I measured an unusually low resistance of a constant value in both directions. Having it low in both directions rules out semiconductor effects inside the devices connected to the circuit you're testing.
In other words, your ability to ascertain a short in a circuit depends on your knowledge of what to expect in that particular circuit. For a logic board like your Mac's, if you see zero to several ohms anywhere on a signal circuit, you can be sure it's a short. A few hundred ohms -- maybe, but you need to investigate whether it is supposed to be like that. Some circuits are driven with open-collector gates (or their CMOS equivalents) and may include a pull-up resistor that will give you that reading (a typical pull-up will be anywhere between a few hundred ohms and a hundred kiloohms). So a few kiloohms will appear like an unlikely short (but be more suspicious if it is symmetric and occurs where you expect to find really high impedance).
For detecting open circuits, you use similar kinds of rules, but you need to be even more aware of semiconductor effects. For an "open", always test in both directions. If you see "infinite" resistance in one direction, but some decidedly finite resistance (hundreds of ohms to kiloohms) in the opposite direction, you've hit a diode or a diode-like structure; possibly lots of them inside participating devices. So it is neither short nor open; it may be a functional signal circuit.
It is only open if it shows "infinity" in both directions, but be aware of normal leaks, because everything on this board -- capacitors and semiconductors -- will leak a bit. So "infinity" can start anywhere from, say, a hundred kiloohms to a hundred megaohms. A gigaohm will be a certified infinity for this type of board, but don't be pedantic: you can introduce a permanent leak on the order of tens of megaohms (or worse) just by touching the board with your fingers (so it's a good idea to wash your hands or put your lab gloves on when working with high-impedance circuits -- although your mac's logic board should not be that sensitive).
Also note, if while testing for an open circuit you see a resistance drifting upwards to infinity, you've probably hit a capacitor that is charging from your meter. If that's so, it will eventually settle at a very high value or will make your meter go out of range.
Finally, note that some semiconductor devices will test as open until you reach a certain breakdown voltage. Try testing an LED, for example. If your meter uses a low test voltage, it may appear like a regular diode, showing open circuit in the reverse direction. But it will show a finite resistance if you meter's test voltage is high enough to light up the LED. Conversely, if it is too low, even a regular diode will appear open in both directions. You need at least 1V to reliably test a diode.
Beware of CMOS gates that are very good at faking an open circuit when commanded open, at any voltage up to hundreds of volts. It may read open, but it does not mean it is faulty.
Some meters use special modes for testing diodes and short-circuits. I have a 20-year old RadioShack multimeter whose short-circuit mode has enough intelligence to give me a beep in most situations that I myself judge as short circuits on close examination. It is a very good first-approximation detector, but I always double-check its readings.
These are just a few things that come to mind -- just to show you why patience is required explaining what's short and what's open.
I forgot to add that, yes it's one of the first thing that came to mind to check but it wasn't because of brightness settings, it must be some fault on board..
Hi tidewatcher,
Yes there did take a lot of patience. Thank you. Unfortunately everything you said was over my head. I just bought this laptop on eBay thinking it would be an easy fix, because it would not power on. Most of the time its just a broken switch or blown fuse. I will spend a little more time trying to figure it out, but it looks like I would have to go to school for a few years to figure out how to fix it. What Ive learned so far has been interesting and I did fix one laptop with a blown fuse and another laptop with a bad switch that had coffee spilled on it.
There is power going to three quarters of the board but no power around the CPU, so there has to be a open or short somewhere. Im not getting low-voltage Im getting 12.5 3.9 or zero voltage and maybe traces of mega voltage in a few spots. Ive checked the fuses but theyre all good.
----------
Thank you that was a big help.
Macbook Pro 15 Early 2011 Fixed & Macbook Air 13 Late 2010 needs keyboard backlight..
Thanks for you help Chigwelldave.
It has been a while and we have already fixed a few Macbook 15 Pro Early 2011. One of them needed new GPU as well as new VRAM installed. That was the tricky one
Other 3 or 4 needed GPU only. Those Early 2011 has 3 different cpu models and also different gpu-s.
A while ago I was looking for a solution to install keyboard backlight on Macbook AIR late 2010. This is only New type Unibody Macbook AIR 13 inches without keyboard backlight
This is off topic here but maybe one of you guys has tried to do it cause I have many customers asking about this mod.
https://forums.macrumors.com/threads/1259159/
Thanks for you help Chigwelldave.
It has been a while and we have already fixed a few Macbook 15 Pro Early 2011. One of them needed new GPU as well as new VRAM installed. That was the tricky one
Other 3 or 4 needed GPU only. Those Early 2011 has 3 different cpu models and also different gpu-s.
A while ago I was looking for a solution to install keyboard backlight on Macbook AIR late 2010. This is only New type Unibody Macbook AIR 13 inches without keyboard backlight
This is off topic here but maybe one of you guys has tried to do it cause I have many customers asking about this mod.
https://forums.macrumors.com/threads/1259159/
Hi mm9
What kind of equipment do you need to replace the GPU? I'm also wondering if they are actually faulty or just need re flowing. I have a board with the non-booting graphics fault and a "working" board I bought to replace it which freezes and reboots when using the discrete GPU. I'm wondering if a hot-air treatment will work (I have nothing to lose). If I get a refund for my lousy "working" board I may get a late 2011 board instead - I haven't heard so many problems with these.
What kind of equipment do you need to replace the GPU? I'm also wondering if they are actually faulty or just need re flowing. I have a board with the non-booting graphics fault and a "working" board I bought to replace it which freezes and reboots when using the discrete GPU. I'm wondering if a hot-air treatment will work (I have nothing to lose). If I get a refund for my lousy "working" board I may get a late 2011 board instead - I haven't heard so many problems with these.
Hi Chigwelldave,
If TPS51125 51125 QFN 24pin Power IC Chip is taken in 3 V & 5 V and is not distributing the voltage then after SMC reset, is its safe to say that part is bad? If I order the part, are there places that will solder it onto the board for me for a reasonable price? What would it generally cost?
There are many problems with those Early 2011 Macbooks. US Apple is already replacing them and maybe shortly will have an worldwide apple replacement program like with Macbook Pro 2007-2008 and Geforce GPU.
You need experience to replace it
If you have it then none special equipment is needed. We dont reflow or reball. We always use a new chip instead old one. Reflowing or reballing might help for some time. I would not recommend learning chip replacing on a macbook logic board. Its too expensive... Its probably better to use some US or CHINA repair option from ebay... Also trying US Apple might be an option.Hi GoTimothy,
The chip you referenced creates the main 3.3 and 5v supplies so, if you have them, it's fine. The 5v supply is one of the last to be sequenced on so I'd take a look at the 'ALL_SYS_PWR_GOOD' (or similar named) signal. This is the final signal AFAIK before the actual boot process. Once the power is all good the system checks the RAM, lights the backlight, chimes etc. Do you get any heat coming from the MCP or CPU? This would hint power is being supplied to these.
Regards,
Chigwelldave.
The chip you referenced creates the main 3.3 and 5v supplies so, if you have them, it's fine. The 5v supply is one of the last to be sequenced on so I'd take a look at the 'ALL_SYS_PWR_GOOD' (or similar named) signal. This is the final signal AFAIK before the actual boot process. Once the power is all good the system checks the RAM, lights the backlight, chimes etc. Do you get any heat coming from the MCP or CPU? This would hint power is being supplied to these.
Regards,
Chigwelldave.
no start
Hi guys
I have here also a isseu
Its a logic board from a macbook pro 1278 with a 2,53Ghz i5 CPU
It had liqued damage.
After cleaning the board ,power for charging the battery is good and loads the battery(when its fully loaded the magsafe turns green)
also the indicator on the side says thats the battery is loaded.
But When i trying to start the macbook nothings happens.
I have also tryed the jumpers on the board its self(nothing)
G3hot is active 3,4V
One jumper gives 3,4 V and the ground is also good 0V
I have also changed the keyboard but the macbook won't start
Can sombody help me with tips(bypassing something)
sorry for my pore englisch (i live in the Netherlands)
Hi guys
I have here also a isseu
Its a logic board from a macbook pro 1278 with a 2,53Ghz i5 CPU
It had liqued damage.
After cleaning the board ,power for charging the battery is good and loads the battery(when its fully loaded the magsafe turns green)
also the indicator on the side says thats the battery is loaded.
But When i trying to start the macbook nothings happens.
I have also tryed the jumpers on the board its self(nothing)
G3hot is active 3,4V
One jumper gives 3,4 V and the ground is also good 0V
I have also changed the keyboard but the macbook won't start
Can sombody help me with tips(bypassing something)
sorry for my pore englisch (i live in the Netherlands)
Attachments
Hi Chigwelldave,
Theres no heat no power no nothing. 3 V and 5 V goes into that chip but its supposed to come out the other side and go to the CPU and USB ports. There is no voltage coming out the other side. I followed the semantics. Is that part a switch, that has to get a signal before it sends out power? How do you check the ALL_SYS_PWR_GOOD signal? Is it in volts, amperage, Ohms or just a zero or one? How do you know if that chip is bad?
Sorry for all the questions but once I check voltage, I dont know what to do next. Theres no voltage coming out of that chip just voltage going into it. Its supposed to send out several lines of 3 and 5 V through the resisters on the bottom, but nothings coming out of them to go to the CPU or USB ports.
When I press the power button, it sends 3.3 V to a chip on top of the board, but when I let go of the power button, the voltage drops back to zero. That chip has to be sending the 3 V to the chip at the top of the board, but then the power drops off, when I let go of the power button.
hi again , on this board what are the 2 pin i have to short to power on pc and bypass the keyboard switch?
im still waithing the 9ahrtz to come from china
This is the same board it shows you. In the left hand bottom corner 3.9v to GND ByPassKeyPwr
http://www.timothean.com/Got.jpg
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Hi GoTomothy,
If we're still talking of U7200, this chip generates the main 3.3 and 5v supplies from the battery (or charger). The supplies are switched further down the line to power other areas. The CPU VCORE is regulated from the battery also, the CPUVTT comes from the 5V supply. Take a look at the POWER BLOCK DIAGRAM (page 3 of the schematic), it will show you each power supply block's input and outputs plus the control signal. The numbers in circles (ASFAIK) are the power on sequence so you can see, for example, the CPU core does not get power until after the RAM. Look for signal 24, this is the ALL SYS power good and should be high (3.4v) to tell the SMC to continue.
It's a long battle tracing the power sequence on these boards, I know - I have a mid 2010 which only gets as far as 3.3v and 0.9.
Regards,
chigwelldave.
tnx for reply, but my board is a bit different...
ive desoldered U7000 and waiting it to come from china. while desoldering 2 capacitors has disappeared as they are so small i didnt notice at first. ordered them too and ill solder them back. hope to get this mainboard fixed asap
Attachments
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tnx very much for the answer. ive tried to short this to jump without success in boot up that macbook. (that before desolder the u7000 chip).
Hi,
Im using a digital meter. Im suspecting the problem could be in the battery indicator circuit (the indicator itself had gone bad too). As i know, the battery isn't recognized without a working battery indicator (or it's circuit). There should be some chip running it, i can't access windows right now, so i can't see my boardview to determine which.
Hi Chigwelldave.
Thanks for the help. Ill check it out. I bought another 2011 MacBook with a throughly smashed top & screen, even bent body on eBay. Everything looks smash but the main board. Ebay-er said It would not charge the battery or boot. But I figured there was a problem with the charger or power supply. I put in a fully charged battery, still no boot off the battery. So when you buy something on eBay, is more than one problem with it. You would think if it wasnt charging the battery, you can put in a fully charged battery and it should boot but no- ooooo. I overpaid $165 bucks and is not one good part on this laptop. Just thought that maybe someone on this board may have bided against me or been the one selling it.
I cant find the power on (debug) pads on the 2011, 13" model, any idea?
Hi GoTimothy,
You can never tell what you're going to get on Ebay but sometimes it's genuine. I look at the seller's feedback and other items to see if they're a dealer or end user. I prefer to buy from a genuine end user. There's a seller in Europe who seems to only sell dead logic boards he has tried to fix but couldn't.
See photo below for the 2011 (late) 13" debug power pads - totally different location to earlier boards.
Attachments
Hello Everybody, I've a mid 2009 Macbook Pro. It is water damaged, but absolutely cleaned after that. It was a long time ago, now the battery is empty.
If I connect the megsafe charger, it turns green, and stay in that state, not change to amber, so not start to charge. The first led of battery is blinking, but not normal, it looks like it is trying to charge, but it can't: two long blink, then a shorter, two long again, and a short... Only the first led is blinking.
When I try to start it, there's nothing, sometimes power led comes alive for a moment, then adter a second it turns off.
If I remove battery, I'm able to start it, but only for 5-15 seconds. Sometimes the login window come up, because it boots very fast with ssd, but never to be able to log in, it turns off before that. Usually it turns off right after the chime.
Is this normal?
But I'm able to start it with the SMC Bypass method, without, and with battery too.
Now I've no other battery to check with.
When I took it from it's previous owner, we tryed it for a while, it was the same. But when I arrived home, I tryed again and it worked! Without SMC bypass, so I saw that the battery was about 85%, but absolutely empty, and the fan was on normal speed. Unfortunatelly I turnd it off, and I wasn't able to start it again in normal mode
Any idea, what should I check/replace first?
Thank you very much!
Edit:
Right after the post, I was able to start the Macbook again, in normal mode!
Just saw this image:
by cmdrdata.
I had nothing to loose, so I tryed to shortcut that 2 pins of the battery, and after that I was able to start it with battery connected. No high fan speed, I see the sensors, I see the battery (88% capacity, 0% charge), but it is not charging yet. Machine goes to sleep if I close the lid. Everything is working except keyboard backlight. Nothing happens if i press F5 or F6. I don't know why.
Little good news for me, is it?
If I connect the megsafe charger, it turns green, and stay in that state, not change to amber, so not start to charge. The first led of battery is blinking, but not normal, it looks like it is trying to charge, but it can't: two long blink, then a shorter, two long again, and a short... Only the first led is blinking.
When I try to start it, there's nothing, sometimes power led comes alive for a moment, then adter a second it turns off.
If I remove battery, I'm able to start it, but only for 5-15 seconds. Sometimes the login window come up, because it boots very fast with ssd, but never to be able to log in, it turns off before that. Usually it turns off right after the chime.
Is this normal?
But I'm able to start it with the SMC Bypass method, without, and with battery too.
Now I've no other battery to check with.
When I took it from it's previous owner, we tryed it for a while, it was the same. But when I arrived home, I tryed again and it worked! Without SMC bypass, so I saw that the battery was about 85%, but absolutely empty, and the fan was on normal speed. Unfortunatelly I turnd it off, and I wasn't able to start it again in normal mode
Any idea, what should I check/replace first?
Thank you very much!
Edit:
Right after the post, I was able to start the Macbook again, in normal mode!
Just saw this image:
by cmdrdata.
I had nothing to loose, so I tryed to shortcut that 2 pins of the battery, and after that I was able to start it with battery connected. No high fan speed, I see the sensors, I see the battery (88% capacity, 0% charge), but it is not charging yet. Machine goes to sleep if I close the lid. Everything is working except keyboard backlight. Nothing happens if i press F5 or F6. I don't know why.
Little good news for me, is it?
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Problem u7000
Hello everyone and congratulations for the forum.
I I apologize for my English.
I have a problem with my bacbook a1278.
Problems encountered:
- Macsafe without connecting the battery the computer will not turn on but the light is green,
- Connecting a low battery, the computer does not turn on, the light is green,
- Connecting a charged battery turn on the computer regularly, green light, suddenly turns off after 2-3 minutes.
- The chip u7000 is very very hot.
here's the picture.
do you think replacing the chip u7000 (visibly damaged) I can solve my problem or the u7000 chip is damaged for other reasons?
I would not change the chip u7000 and the problem is another.
I ask for your help please
Hello everyone and congratulations for the forum.
I I apologize for my English.
I have a problem with my bacbook a1278.
Problems encountered:
- Macsafe without connecting the battery the computer will not turn on but the light is green,
- Connecting a low battery, the computer does not turn on, the light is green,
- Connecting a charged battery turn on the computer regularly, green light, suddenly turns off after 2-3 minutes.
- The chip u7000 is very very hot.
here's the picture.
do you think replacing the chip u7000 (visibly damaged) I can solve my problem or the u7000 chip is damaged for other reasons?
I would not change the chip u7000 and the problem is another.
I ask for your help please
A1278 macbook pro 13 mid2010 820-2879-B
Hello everybody I'm Vic 44
I've been reading this thread for days now and wondered if someone could help me. I'm trying to repair my daughters MacBook pro mid 2010 unibody,at first I had green light on magsafe and battery was charged fine just wouldn't start. So I was checking on the board with my probes and magsafe on and no battery when I shorted something out, now NOTHING. I thought I had blown the magsafe, so bought a new DCIN board but still the same. I have been trying to follow the schematic K6 for this board but I don't understand what I've got on R7020 could you please take a look at the attachments and advise accordingly.
P.S. Your all doing a grand job. Thanks Vic44.
Hello everybody I'm Vic 44
I've been reading this thread for days now and wondered if someone could help me. I'm trying to repair my daughters MacBook pro mid 2010 unibody,at first I had green light on magsafe and battery was charged fine just wouldn't start. So I was checking on the board with my probes and magsafe on and no battery when I shorted something out, now NOTHING. I thought I had blown the magsafe, so bought a new DCIN board but still the same. I have been trying to follow the schematic K6 for this board but I don't understand what I've got on R7020 could you please take a look at the attachments and advise accordingly.
P.S. Your all doing a grand job. Thanks Vic44.
Hi Vic44,
You may be lucky and just blown the fuse (F6905 next to the ethernet port). If that is OK you should have 16-18v on R7020 if U7000 is working properly. But as you have 11.7v from your battery, the Mac should start so you will have issues downstream to look at once you fix the mag safe problem. Refer page 3 of the schematic - this shows all the required power supplies and their sequence. Q7055 voltages look correct with a disconnected mag safe.
Regards,
Chigwelldave.