820-00165 No SLP

bjf

Member
I'm getting my ass handed to me by this 2015 Air board. It had very light corrosion scattered in a few places, mostly around the 3V42 circuit and other PPBUS components, but not near the ISL6259 charging area, that all looks perfect and measures normally (voltage, diode.) 3V42 and PPBUS were always there and did not require any repairs to get them going. I have a normal MagSafe light, SMC reset works fine, SMC bypass causes a millisecond fan spin.

I've repaired and replaced components in every area that was even slightly damaged just to make sure there was nothing unexpectedly causing a failure. I've taken diode measurements against a good board and can't find anything off. I've reached the end of what I can do with it so if anyone has a helpful idea for a next step it would be greatly appreciated.

I have:
• 3V42
• PPBUS
• PPVRTC
• 5V_S5
• 3V3_S5
• 3V3_SUS
• PP1V05_SUS

I don't have:
• PP5V_S4RS3 (0V)
• PP3V3_S4 (0.346V)
• Every other voltage line on the Power Aliases page
 

larossmann

Administrator
Staff member
Does it turn on if you remove C1300 & C1303? do you have any corroded traces by U6100? Follow where they go. This has all the right problems to be an unsolvable nightmare, but let's try.
 

bjf

Member
No luck. No change after removing C1300 and C1303. And the U6100 area looks perfect. All lines are making their way to the next junction and so far everything there looks good too. I did originally change U1900 because SYSCLK_CLK25M_X2_R was at 0.025V and SYSCLK_CLK25M_X1 is at 0.65V. No change after replacing that though.

This is hard because the areas that had corrosion seem pretty innocuous as far as the board turning on. The one thing that I think is hurting the cause is that there were tiny amounts of corrosion in a few different areas. It definitely wasn't concentrated on just one area, but it was things like backlight, PPBUS and 3V42.
 

dukefawks

Administrator
It must be pulsing power if the SMC bypass can cause fan spin. Check all data lines to BIOS chip and check if ALL_SYS_PWRGD gives a millisecond pulse.
 

george-a

New member
I have a similar problem, LD, UC => no power on, no fan spin.

Green/Orange light OK, PPBUS_G3H and PP3V3_S5 ok, I can measure lots of activity around the SMC including 32KHz clock, also PP5V_S5 ok.

3V3_SUS and PP1V05_SUS also OK.

BIOS chip looks good, signals - voltages present.
 
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george-a

New member
Apologies, I thought that was the point, NOT to start new threads when a topic is already there with similar or same issue. Also I noticed those ones where unanswered for a long time and maybe there was a point in resurrecting them.

Again please accept my apologies, I didn't mean to make a mess, the contrary.

EDIT: also if you noticed on the other thread (https://www.rossmanngroup.com/board...eshooting/4099-820-00165-macbook-air-no-power), our friend completed the discussion by adding how he reached a solution - even if it was "voodoo" as he said. And this is helpful for everybody, you for example dont need to answer the same questions all the time and we just do a search instead of thread flooding.
 
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bjf

Member
Just wanted to add a thought to this. I think both sides are right. I think there are TWO distinct ways to add to a current thread. One is to add your issue that is close or similar to the original poster's, and the second is to say something like, "I have the exact same problem, any progress?' The former gets chaotic pretty fast, while the latter feels reasonable and is sometimes helpful for people involved. I think the key is that it really needs to be the exact same issue. Once you start posting things like, "this is what's happening to mine" the thread gets convoluted. Hope that helps. btw, I'll update this once I ever get a chance to get back to this board.
 

bjf

Member
U1900 is putting out around 0.7V on SYSCLK_CLK25M_X1 and 0.01V on SYSCLK_CLK25M_X2_R

It has 0V on both PP1V2_CAM_XTALPCIEVDD and PP3V3_TBTLC.

Not sure which power rails I should be fighting for here. Does anyone know if U1900 will still output the clock signals (SYSCLK_CLK25M_X1 and SYSCLK_CLK25M_X2_R) even it's missing PP1V2_CAM_XTALPCIEVDD and PP3V3_TBTLC?
 

dukefawks

Administrator
You did not answer my questions from post #4. I still say resistors in SPI ROM data lines or corroded trace around there.
 

bjf

Member
Sorry, missed that. Yes, ALL_SYS_PWRGD shoots up to about 2.6V for a split second and drops right down. All of the pins except ground on the BIOS chip are getting 3.3V but I'm assuming that doesn't tell me enough?
 

dukefawks

Administrator
Does CPU Vcore come on briefly too? If yes then go and check all traces and resistors to the SPI ROM. There are a bunch of resistors in series with the data lines.
 

bjf

Member
CPU Vcore is not coming on. After trying it multiple times I can see a 0.001V blip. Not sure if that would qualify as anything meaningful, but that's all I'm getting.
 

bjf

Member
Pin 8 has 3.42V. Pins 1 and 2 have 0.06V. All other pins are measuring 0V. U1950 and the area around it looks good. Doesn't look like it got hit by anything.
 

dukefawks

Administrator
Pin 1 and 2 should get a pulse on there. Best to check on pin 7, it should get a pulse just like you measured elsewhere.
 

bjf

Member
Pin 7 and 1 get a pulse that got up to about 1V at times - usually around 0.5V. Pin 2 got up to almost 3V some of the time.
 
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