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Old Jul 20, 2011, 08:43 PM   #126
cmdrdata
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Originally Posted by Dadioh View Post
The DVD drive is an easy fix but would have been nice if it worked.
@Dadioh, if you meant replacing the unit, yes, it is quite easy, just a few screws. I opened my superdrive, but can't see anything obvious. All the movable parts are movable manually, so I am not sure what else I can check. Have you manage to repair one at that level? I do have a replacement unit on order, so it is just a matter of days before I get everything working.
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Old Jul 20, 2011, 08:55 PM   #127
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@Dadioh, if you meant replacing the unit, yes, it is quite easy, just a few screws. I opened my superdrive, but can't see anything obvious. All the movable parts are movable manually, so I am not sure what else I can check. Have you manage to repair one at that level? I do have a replacement unit on order, so it is just a matter of days before I get everything working.
Yes. I meant replacement. However, I had one that was acting wonky (technical term) and I fixed it by opening it up and cleaning the laser lense. I looked at it under my microscope and I could see dust on the lens. After cleaning everything worked great. But in that case the behaviour was not reading discs properly. I think you said yours was ejecting disks after trying to read them? Might be worth a shot cleaning it.

I use a q-tip with 99% isopropyl alcohol. I twirl the q-tip in the centre of the lens. Let it dry for a few minutes and give it a shot.
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Old Jul 21, 2011, 01:07 PM   #128
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I think you said yours was ejecting disks after trying to read them? Might be worth a shot cleaning it.
Here's what mine does:

I insert a disk and when it gets to a certain point where I think a normal drive would do, it doesn't grab and suck it in. I have to go almost all the way before it pulls just enough to go in but never all the way to the disk spindle. Then after some noises, it would spit it back out. So it really never got to the point of attempting to read. I think the disk is just not being positioned correctly, so the center spindle never even got a chance to pop-up and spin the disk, much less attempting to read it. The new one should arrive Saturday!
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Old Jul 22, 2011, 09:18 AM   #129
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Here's what mine does:

I insert a disk and when it gets to a certain point where I think a normal drive would do, it doesn't grab and suck it in. I have to go almost all the way before it pulls just enough to go in but never all the way to the disk spindle. Then after some noises, it would spit it back out. So it really never got to the point of attempting to read. I think the disk is just not being positioned correctly, so the center spindle never even got a chance to pop-up and spin the disk, much less attempting to read it. The new one should arrive Saturday!
Both the battery indicator and superdrive arrived in the mail yesterday. I installed both, and the MBP is now 100% functional. I was able to upgrade the OSX to Snow Leopard. Next upgrade is 500GB drive and possibly OSX Lion. Thanks to everyone who contributed to this forum.

My next project: the currently "dead" 15" MBP ( A1260, circa 2008).
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Old Jul 24, 2011, 11:44 PM   #130
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Macbook unibody power problems

Hey,I've got 2 A1278's here that don't boot & the fan will spin fast with the battery installed.They both have IC's that heat up & from what i can tell they are bios chips.Is there any way to test if these chips are good or what voltage they should have on the pins.Could this be the reason the laptop won't boot?Where would you get the bios chip programed if it was bad or could i use one off an A1181?Here's the info if someone could help,same boards but different chips.Thanks
sst 25vf032b
50-4c-52af
0637100a

mx 12g
25l3205dm21
2y304300
taiwan
l083536
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Old Jul 25, 2011, 01:08 AM   #131
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I see this as an ongoing thread that may be a useful resource for those googling for help. The non-charging logic boards that I have fixed were mostly just cleaning up the liquid residue and restoring function. I did have one that had a part melt on me while I watched. I connected the magsafe and while I was watching this part glowed bright and caught my eye. Sure enough it was fried when I looked under the microscope. I replaced it with a spare from one of my dead cards and the logic board worked fine after that. It was a while back and I can't remember what device it was on the schematic now (guess I killed those particular brain cells

A non-charging battery can be a lot of different things. The place to start is looking at the ISL6258A and see if it is trying to run the boost circuit. I think the datasheet is available below. I think Apple may get a custom version and change the part number.

http://www.intersil.com/data/fn/fn6396.pdf
Hello Dadioh
Before you seen the part glowing,what was the board doing or not doing?Would it power with battery?Would it charge battery?Would it power with cord?Was it a diode?Do you know where that part is located on late 2008 unibody?
Thanks
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Old Jul 27, 2011, 09:24 AM   #132
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Hey,I've got 2 A1278's here that don't boot & the fan will spin fast with the battery installed.They both have IC's that heat up & from what i can tell they are bios chips.Is there any way to test if these chips are good or what voltage they should have on the pins.
Here's an idea: the left and right fan control for MBP comes from the SMC, however, these signals are gated by MOSFETs (Q5660 and Q5661, P/N 2N7002. AFAIK, A1278 only has ONE fan, so my schematic may not be exactly right, but good enough for discussion purposes. The fan is powered by 5v with these connector pinout:
1 - 5v input
2 - Tach output (fan speed to SMC)
3 - Fan speed control
4 - Ground

Since you are getting full fan speed, check pin 3 and see what voltage you see there. Normally this should be an "average" DC output of what the SMC think it should be as the SMC signal is pulse width modulated (PWM). In your case, it could be a steady logic signal. A scope (or logic probe) would have been very useful here. Backtracking, the SMC signal (FAN_CTL_0 or 1) is pulled up to 3.3v before wired to the SOURCE pin of the MOSFET and the GATE is always enabled by virtue of direct connection to 3.3v.

Thus using the "bypass" method indicated in the first message of this forum, SMC is probably not sending the FAN_CTL signal. Your no-boot state indicate a problem elsewhere. There is a logic gate that tell the system that "all" voltages are ok. I'd check that too.
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Old Jul 27, 2011, 07:52 PM   #133
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Originally Posted by cmdrdata View Post
Here's an idea: the left and right fan control for MBP comes from the SMC, however, these signals are gated by MOSFETs (Q5660 and Q5661, P/N 2N7002. AFAIK, A1278 only has ONE fan, so my schematic may not be exactly right, but good enough for discussion purposes. The fan is powered by 5v with these connector pinout:
1 - 5v input
2 - Tach output (fan speed to SMC)
3 - Fan speed control
4 - Ground

Since you are getting full fan speed, check pin 3 and see what voltage you see there. Normally this should be an "average" DC output of what the SMC think it should be as the SMC signal is pulse width modulated (PWM). In your case, it could be a steady logic signal. A scope (or logic probe) would have been very useful here. Backtracking, the SMC signal (FAN_CTL_0 or 1) is pulled up to 3.3v before wired to the SOURCE pin of the MOSFET and the GATE is always enabled by virtue of direct connection to 3.3v.

Thus using the "bypass" method indicated in the first message of this forum, SMC is probably not sending the FAN_CTL signal. Your no-boot state indicate a problem elsewhere. There is a logic gate that tell the system that "all" voltages are ok. I'd check that too.
Hello...Pin 3 only has .26 volts,Pin 4 has 5 volts & Pin 2 has 4.7 volts.
I found the mosfet Q5660 on the 15 inch model & its real close to the fan plug.It's marked k72v9.On the A1278 the only chip that I can find that's maybe connected to fan is on the opposite side of the board & it's marked k6nv9.It's real hard to check voltage on it cause its small & in a hard spot to get to.I could only find like .56 volts on one of the pins.I could find find 3 volts on one side of a near by resistor & .56 on the other side.The resistor measures 19.89 k.I get the same measurements on both boards.
I did find the k72v9 mosfet on the a1278 but it's on the bottom just in from the mini display port.Not sure what it's for.
Thanks for your input on my post.Maybe I should try to get my 15 inch going first since we have the schematic & it seems like you know how to read it & ask the right questions.Thanks again

Forgot to mention,both the boards will burn up a 470 resistor just down from the lcd connector when plugged in.

Last edited by peislander; Jul 28, 2011 at 12:16 AM.
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Old Jul 28, 2011, 11:55 AM   #134
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Hello...Pin 3 only has .26 volts,Pin 4 has 5 volts & Pin 2 has 4.7 volts.
I found the mosfet Q5660 on the 15 inch model & its real close to the fan plug.It's marked k72v9.On the A1278 the only chip that I can find that's maybe connected to fan is on the opposite side of the board & it's marked k6nv9.It's real hard to check voltage on it cause its small & in a hard spot to get to.I could only find like .56 volts on one of the pins.I could find find 3 volts on one side of a near by resistor & .56 on the other side.The resistor measures 19.89 k.I get the same measurements on both boards.
I did find the k72v9 mosfet on the a1278 but it's on the bottom just in from the mini display port.Not sure what it's for.
Thanks for your input on my post.Maybe I should try to get my 15 inch going first since we have the schematic & it seems like you know how to read it & ask the right questions.Thanks again

Forgot to mention,both the boards will burn up a 470 resistor just down from the lcd connector when plugged in.
Your description of the connector is "reversed" from the schematic, so I think when you saw 5v on pin4, that is really pin1, and so forth. My guess at this point is that there is a power issue in the logic board that prevents the system from booting. Maybe you have a shorted MOSFET or IC that are internally burned out (is this a water damaged logic board and if so, a high probability). On the 470 Ohm resistor, are you sure it should be 470? It seemed way too low value. For example, the signal lines to the SMC have series resistors that are usually around 47k Ohm, not 470. The low valued resistors are mostly around the charging circuitry.
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Old Jul 28, 2011, 01:58 PM   #135
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Your description of the connector is "reversed" from the schematic, so I think when you saw 5v on pin4, that is really pin1, and so forth. My guess at this point is that there is a power issue in the logic board that prevents the system from booting. Maybe you have a shorted MOSFET or IC that are internally burned out (is this a water damaged logic board and if so, a high probability). On the 470 Ohm resistor, are you sure it should be 470? It seemed way too low value. For example, the signal lines to the SMC have series resistors that are usually around 47k Ohm, not 470. The low valued resistors are mostly around the charging circuitry.
I just guessed i had pin 3 correct because there's white dot on mobo to check voltage of i thought pin 3.I got the other voltages measuring right on the fan connector.Yes i believe it's a mosfet,IC or even just a cap or resistor.I just need to know where to check for problems.Yes they are water damaged but after cleaning they don't look that bad.I've been using a liquid damaged a1278 that i fixed over a year ago.If you looked at the motherboard close you wouldn't believe it worked with all the burnt looking smd's.

Yes its a 470 ohm resistor for sure.It's marked 470 on top.On one side there's a 330w inductor & on the other side is the TDK 6T2113HF chip.Just for a reference point.Thanks
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Old Jul 28, 2011, 02:22 PM   #136
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Yes its a 470 ohm resistor for sure.It's marked 470 on top.On one side there's a 330w inductor & on the other side is the TDK 6T2113HF chip.Just for a reference point.Thanks
You're close to the problem I think. In electronic parlance, resistor numbering on the part sometimes says 470 where the 3rd digit means how many ZEROes. Thus that resistor is probably 47 Ohm (a 471 means 470 Ohms, and 472 means 4.7kOhms). There is a 47 Ohm resistor that feeds the dual diode that becomes the 3.432 G3HOT always on power supply, and this one happens to be the current limiter from the AC power supply! The common cathode of these two diodes feeds an LT3470 (a voltage regulator) that generates the 3.43v G3HOT supply (filtered by probably that big inductor you mentioned, a 33uHenry inductor (inductance unit is in microHenry, not Watts.)

you've got a shorted components somewhere in/near the 3.42v supply which is always connected to AC or battery power. That TDK part is 1.8v voltage regulator, one of the supply with signal name PP1V8. And if you recall old resistor color code: yellow-violet-black = 470 = 47 Ohm.

I think I need to correct myself: there are TWO 1.8v regulator. One is lower current, the other is much higher current, a PWM system driven by Intersil part (6236) that drives two MOSFETs high and low creating a pulse train that are then smoothed by an inductor/cap combination (page 82). Your problem may not be here. A high current draw on the 47 Ohm resistor needs to traced to which component is doing it.

Last edited by cmdrdata; Jul 28, 2011 at 03:29 PM. Reason: more info about 1.8v
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Old Jul 28, 2011, 08:46 PM   #137
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You're close to the problem I think. In electronic parlance, resistor numbering on the part sometimes says 470 where the 3rd digit means how many ZEROes. Thus that resistor is probably 47 Ohm (a 471 means 470 Ohms, and 472 means 4.7kOhms). There is a 47 Ohm resistor that feeds the dual diode that becomes the 3.432 G3HOT always on power supply, and this one happens to be the current limiter from the AC power supply! The common cathode of these two diodes feeds an LT3470 (a voltage regulator) that generates the 3.43v G3HOT supply (filtered by probably that big inductor you mentioned, a 33uHenry inductor (inductance unit is in microHenry, not Watts.)

you've got a shorted components somewhere in/near the 3.42v supply which is always connected to AC or battery power. That TDK part is 1.8v voltage regulator, one of the supply with signal name PP1V8. And if you recall old resistor color code: yellow-violet-black = 470 = 47 Ohm.

I think I need to correct myself: there are TWO 1.8v regulator. One is lower current, the other is much higher current, a PWM system driven by Intersil part (6236) that drives two MOSFETs high and low creating a pulse train that are then smoothed by an inductor/cap combination (page 82). Your problem may not be here. A high current draw on the 47 Ohm resistor needs to traced to which component is doing it.
Yes you are correct about the 47 ohm resistor..I just never payed attention to the dot.It reads like 47.8 or even 46.8.I just assumed it was 470 because of the markings.Yea I learned something today.Thank you

I found what i believe is the voltage regulator on opposite side of board under the 47 ohm resistor.It's marked LTBDM.Would pins 4,6 & 8 be ground?I tested both boards & found ground on these pins.I see another chip beside the voltage regulator that i think is the dual diode.I think it's marked A1.On both board's it looks a little burnt & on one board the regulator looks a bit burnt,but like i said before just cause it looks burnt it's not always burnt.

Does line voltage come to the voltage regulator or diode first?I have continuity between the 47 ohm resistor & the diode.The diode's tested good on the board but do i need to take them off to check?What is the power track i guess is what i need to find & see where it stops.Thanks
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Old Jul 28, 2011, 09:41 PM   #138
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Yes you are correct about the 47 ohm resistor..I just never payed attention to the dot.It reads like 47.8 or even 46.8.I just assumed it was 470 because of the markings.Yea I learned something today.Thank you

I found what i believe is the voltage regulator on opposite side of board under the 47 ohm resistor.It's marked LTBDM.Would pins 4,6 & 8 be ground?I tested both boards & found ground on these pins.I see another chip beside the voltage regulator that i think is the dual diode.I think it's marked A1.On both board's it looks a little burnt & on one board the regulator looks a bit burnt,but like i said before just cause it looks burnt it's not always burnt.

Does line voltage come to the voltage regulator or diode first?I have continuity between the 47 ohm resistor & the diode.The diode's tested good on the board but do i need to take them off to check?What is the power track i guess is what i need to find & see where it stops.Thanks
The line voltage (magsafe power) is routed through the 47 Ohm resistor and "OR-ed" with battery power (the ntwo DIODE thing) to ALWAYS generate G3HOT low current signal. This G3HOT is 3.42v, an output from a voltage regulator chip made by Linear Technology p/n LT34570A. This output is only to provide power to the SMC so it can respond to various power control stimulus. According to the schematic, it is only designed to supply 3.425v at 250mA max. So if G3HOT is correct, the SMC and other critical components powered by G3HOT for example with the battery connected, when it sees a magsafe connected will then communicate with the adapter and if all is well turn on the 16.5v by enabling the inrush and reverse current MOSFETs. Recall I mentioned in previous post that the magsafe only output the 16.5v if it sees a low impedance load. Well, turning on the two MOSFETs is equivalent to loading the magsafe line because on the other side of the MOSFET is input to the 12V system bus power regulator that supply power to the system board functions. If you follow the raw DC in line, it goes to another pair of MOSFETs that is controlled by the IC made by Intersil, ISL 6278A. This chip also control the battery charger (yet another MOSFET). The MOSFET regulates the charging current to the battery. Of course the SMC also control the turning on of the logic board by sensing other inputs like power on switch, other voltage regulators output, SODIMM and other stuff. So the SMC can prevent power up if any of the sensing items it monitors are not up to par.

About battery power only: it seemed that 12v bus (AC or BATT, or BOTH sourced) is the main supply that in the end powers everything else in the system. If the system only works with AC, then BATT power and charging which is gated by MOSFET Q7055 or (Q7056 in 15" model) is not allowing juice to flow. On the other hand, if it works with BATT but not AC, then the MOSFETs I described earlier are the gates that disable AC power from gating it to the 12v bus.

Last edited by cmdrdata; Jul 29, 2011 at 06:42 AM.
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Old Jul 30, 2011, 09:34 PM   #139
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The line voltage (magsafe power) is routed through the 47 Ohm resistor and "OR-ed" with battery power (the ntwo DIODE thing) to ALWAYS generate G3HOT low current signal. This G3HOT is 3.42v, an output from a voltage regulator chip made by Linear Technology p/n LT34570A. This output is only to provide power to the SMC so it can respond to various power control stimulus. According to the schematic, it is only designed to supply 3.425v at 250mA max. So if G3HOT is correct, the SMC and other critical components powered by G3HOT for example with the battery connected, when it sees a magsafe connected will then communicate with the adapter and if all is well turn on the 16.5v by enabling the inrush and reverse current MOSFETs. Recall I mentioned in previous post that the magsafe only output the 16.5v if it sees a low impedance load. Well, turning on the two MOSFETs is equivalent to loading the magsafe line because on the other side of the MOSFET is input to the 12V system bus power regulator that supply power to the system board functions. If you follow the raw DC in line, it goes to another pair of MOSFETs that is controlled by the IC made by Intersil, ISL 6278A. This chip also control the battery charger (yet another MOSFET). The MOSFET regulates the charging current to the battery. Of course the SMC also control the turning on of the logic board by sensing other inputs like power on switch, other voltage regulators output, SODIMM and other stuff. So the SMC can prevent power up if any of the sensing items it monitors are not up to par.

About battery power only: it seemed that 12v bus (AC or BATT, or BOTH sourced) is the main supply that in the end powers everything else in the system. If the system only works with AC, then BATT power and charging which is gated by MOSFET Q7055 or (Q7056 in 15" model) is not allowing juice to flow. On the other hand, if it works with BATT but not AC, then the MOSFETs I described earlier are the gates that disable AC power from gating it to the 12v bus.
Is the voltage regulator p/n LT34570A that you mentioned the same regulator that you mentioned in an earlier post,that I thought was LTBDM?The LTBDM should only be grounded on pin 4.I got ground on pins 4,6,& 8 on 3 boards.I remembered I had an apple A1181 on the shelf with the same problems.It's got the same 47 ohm resistor burning out & i have ground on pin's 4,6 & 8 of the same LTBDM voltage regulator.I removed the LTBDM off the motherboard & pad's 6 & 8 still shorted.I removed a couple other component's close by that had continuity to them but still have the shorted pads.

Thanks for all your info.I don't know if I'll ever get this figured out but nothing ventured nothing gained.Later
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Old Jul 30, 2011, 10:01 PM   #140
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The voltage regulator on pin 4 has to be connected to the GROUND!!!

Welcome to the real world, jackass!

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Old Jul 31, 2011, 09:21 PM   #141
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Is the voltage regulator p/n LT34570A that you mentioned the same regulator that you mentioned in an earlier post,that I thought was LTBDM?
I tend to make typos when typing. The part I intend to quote was LT3470A, not LT34570A. I also don't have an answer for LTBDM. Haven't got a clue what that is. Most ICs are identified by letter and numbers. Can you tell me what page of your schematic it was showing at? For example, an IC number like U7000 is the Intersil ISL6258A is the battery charger IC.

Just a hunch, IC pads that are measuring shorted/connected together and are grounded is probably an intentional ground. If they are not supposed to be and measured shorted to ground, you might as well use parts from that board for part. Multilayer traces are almost impossible to repair.
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Old Jul 31, 2011, 10:06 PM   #142
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I tend to make typos when typing. The part I intend to quote was LT3470A, not LT34570A. I also don't have an answer for LTBDM. Haven't got a clue what that is. Most ICs are identified by letter and numbers. Can you tell me what page of your schematic it was showing at? For example, an IC number like U7000 is the Intersil ISL6258A is the battery charger IC.

Just a hunch, IC pads that are measuring shorted/connected together and are grounded is probably an intentional ground. If they are not supposed to be and measured shorted to ground, you might as well use parts from that board for part. Multilayer traces are almost impossible to repair.
Hi,It's the u6990 that is marked LTBDM. R6905 is the 47 ohm resistor that burns up.That's on the 15 inch schematic ..Yes these boards may be best for parts but that's why i thought I would work/learn on since most of my other boards at least post.I thought it maybe another component causing pads 6 & 8 to short out.
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Old Aug 1, 2011, 09:14 AM   #143
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Hi,It's the u6990 that is marked LTBDM. R6905 is the 47 ohm resistor that burns up.That's on the 15 inch schematic ..Yes these boards may be best for parts but that's why i thought I would work/learn on since most of my other boards at least post.I thought it maybe another component causing pads 6 & 8 to short out.
OK, based on your description, THAT is the G3HOT voltage regulator that generates teh 3.425 voltage (always on if battery or magsafe is connected). THE ONLY hard ground you should see there (zero Ohm) are pins 5 and 9). Pins 6 and 8 are "Vcc" meaning that is the power input pins and is by design connected together, getting the power from the two diodes. Pin 4 should NOT be ground as it is the "output of that chip that is followed by a choke L6995 then the "system load" consisting of a few ICs like the SMC, the battery charger, etc. At this point you have three possibilities:

1. U6990 is bad (internally shorted)
2. One or more of the 3.42v LOAD is shorted to ground (IC, capacitor, etc).
3. The trace in the PC board is bad (PP3V42_G3H traces).

Removing L6995 will allow you to isolate where the short is. With this choke removed, you should see low resistance ( i.e., this supply has a design limit of 3.425v@250mA max, so the load resistance total should be no lower than 3.425/.250 = ~13 Ohm (Basic electronic equation of V=IxR).
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Old Aug 3, 2011, 09:49 AM   #144
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Removing L6995 will allow you to isolate where the short is. With this choke removed, you should see low resistance ( i.e., this supply has a design limit of 3.425v@250mA max, so the load resistance total should be no lower than 3.425/.250 = ~13 Ohm (Basic electronic equation of V=IxR).

Got L6995 removed on two boards.It removed the short on pad 8.Still have short on pad 6.Where should I be seeing the low resistance you mentioned?Where do I measure the load resistance?I removed the 47 ohm resistor's too cause they are burnt & out of tolerance.Should I replace the resistor & plug board in & see if resistor still burns with L6995 removed or look for heating parts?Thanks
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Old Aug 3, 2011, 01:51 PM   #145
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Removing L6995 will allow you to isolate where the short is. With this choke removed, you should see low resistance ( i.e., this supply has a design limit of 3.425v@250mA max, so the load resistance total should be no lower than 3.425/.250 = ~13 Ohm (Basic electronic equation of V=IxR).

Got L6995 removed on two boards.It removed the short on pad 8.Still have short on pad 6.Where should I be seeing the low resistance you mentioned?Where do I measure the load resistance?I removed the 47 ohm resistor's too cause they are burnt & out of tolerance.Should I replace the resistor & plug board in & see if resistor still burns with L6995 removed or look for heating parts?Thanks
First off, I just noticed that LT3470-ETS8 on the A1286 DOES NOT have the same pinout as the LT3470-A in A1287, so my explanation is based on the A1287 alone.

Measuring on "pin2 pad" of L6995 is the "load" side of the power supply. If you see a much lower resistance here, lift off pin2 (BIAS pin) of the LTBDM chip to further isolate the LTBDM from the load side (this is the BIAS input to the chip so that it can maintain the "3.425v output".

If you get around 13 Ohms or more, then the LTBDM is most likely shorted internally. I assumed that when you are measuring these shorts, the LTBDM have not been removed from the board? According to the chip spec, pin4 (SW pin) output voltage is set by the formula: Vout = 1.25 x (1+ R1/R2). Pin1 is the FB line of this chip, and should not be zero/ground. The fact that you've got ground on pin6 (again based on 1A1287), points to a bad LTBDM chip. If you remove this chip altogether and measure pin4, 6 and 8 pads, they should be open circuit to ground. My guess: after removing the chip and installing a new 47 Ohm resistor, that 47 Ohm should be fine when the adapter or battery is connected.
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Old Aug 13, 2011, 06:25 PM   #146
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Hi,could you help me identify what the tan coloured part is below your 18.5 volt test.Is it a capacitor and should it test high continuity or no reading,which is what i`m getting.Thank you
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Old Aug 13, 2011, 10:41 PM   #147
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Hi,could you help me identify what the tan coloured part is below your 18.5 volt test.Is it a capacitor and should it test high continuity or no reading,which is what i`m getting.Thank you
That's a capacitor so it should measure open circuit on an ohmmeter.
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Old Aug 14, 2011, 05:40 AM   #148
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Hi dadioh,it doesn`t measure an open circuit.Could you tell me what the cap is please.Sorry for blurry pic .I`m doing basic testing at the moment while i wait for a new charger.
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Old Aug 14, 2011, 08:02 AM   #149
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Hi dadioh,it doesn`t measure an open circuit.Could you tell me what the cap is please.Sorry for blurry pic .I`m doing basic testing at the moment while i wait for a new charger.
The meter is showing an open circuit. Open circuit = infinite resistance (well large anyways). A capacitor passes very little DC current by design. Therefore resistance is large. On your meter open circuit is needle all the way to the left (top scale infinity symbol). Short circuit = resistance zero (or very low). That would be needle all the way to the right (top scale zero ohms).

So that cap is OK as far as leakage current goes which probably means it is OK. It is possible it has failed open circuit but that is not very common and you would need a capacitance meter to verify that.

edit: what is the issue you are trying to solve?
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Old Aug 15, 2011, 12:19 PM   #150
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MacBook Pro 13" 2.26 A1278 caps lock power issue

I have above MacBook that is behaving strangely and wondering if anyone else has had a similar issue. It may have had liquid ingress and been cleaned previously but I cannot tell. Laptop powers up in safe mode only. Can only type in upper case but can type in upper & lower case when using an external USB keyboard . Caps lock light works but does not change upper or lower case. Have tried with a another working keyboard but same fault. Also seems to be an issue with audio socket. Also the power button will not power the laptop down for some reason. Have downgraded EFI from 1.7 to 1.6, details here: http://forums.macrumors.com/showpost...&postcount=305 but problems still persist. Anyone have any idea what could be causing these unusual problems?
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