MBAir 13” A1466 missing SPI clock

[fichamba]

Hello everybody:
I have an A1466 (MoBo 820-00165-A) which is driving me crazy.
It has all voltages, everything seems OK. It starts after connecting the Apple charger (fan spins normally; maybe a bit later than in a working board that I have side by side). The only (!!!) missing signal is the SPI clock.
I have measured at pin 6 of U6100 (the SPI), and I have nothing in the scope. Neither in the data in/out pints I have data train in the scope (just a little bit sometimes).
The working board is showing me fixed clock pulse at pin 6 of its SPI. I'm crazy about this. I had cleaned and reballed the SMC, but still the same effect: missing clock.
I've checked all terminators (all low ohm values), and everything looks and read fine (following both the schematic and re-checking it in the working board).
I will appreciate any kind of help in this regard.
TIA!!

[mon2]

Re: MBAir 13” A1466 missing SPI clock

The SPI clock has some series current limit resistors. Confirm that each is present and functional.

The SPI clock will have a SPI master, confirm that the SPI master is spitting out the clock pulse stream.

Also, suggest to remove the trackpad as it may be tanking this clock line.

If still no joy, remove all power -> meter in resistance mode (2k scale).

Check the resistance to ground of this SPI clock line. Perhaps something is causing an excessive load to prevent the line from pulsing properly.

[fichamba]

Re: MBAir 13” A1466 missing SPI clock

The SPI clock has some series current limit resistors. Confirm that each is present and functional.

The SPI clock will have a SPI master, confirm that the SPI master is spitting out the clock pulse stream.

Also, suggest to remove the trackpad as it may be tanking this clock line.

If still no joy, remove all power -> meter in resistance mode (2k scale).

Check the resistance to ground of this SPI clock line. Perhaps something is causing an excessive load to prevent the line from pulsing properly.

Thanks a lot for your guidelines, mon2.
I am working with the bare board, so nothing connected (trackpad).
I will check again terminations, because the SPI clock line resistance to ground is exactly the same as in the working board.

Cheers

[mon2]

Re: MBAir 13” A1466 missing SPI clock

Try this - remove one of the series resistors between the SPI master & SPI slave(s).

Then probe with your scope, the SPI master to see if there is a presence of the SPI CLK upon a power up.

[fichamba]

Re: MBAir 13” A1466 missing SPI clock

OK. I'm with it, working now in the bench. Madrid, Spain. Thanks a lot again.

[piernov]

Re: MBAir 13” A1466 missing SPI clock

Must check power rails & power sequence first.

[reformatt]

Re: MBAir 13” A1466 missing SPI clock

Check resistance of L7630 to ground, what is it's value? From experience, under 150 ohms is usually a damaged PCH so results in a brain dead board (generally from liquid damage to PP1V05 converter). IIRC, PCH begins the SPI read, then this passes to CPU.

Also check continuity of traces between resistors from U6100 area to CPU R6110~R6113, R6118, R6119.

[fichamba]

Re: MBAir 13” A1466 missing SPI clock

Hello again, and first of all thanks for your help.

I have checked everyting (but piernov and reformatt suggested, which I will do it just now), and still no luck. Everyting seems fine, fan starts as normally, overall temperature is extremely similar to the working board (I have it side by side with the non working one). Even more: I have changed also...the Xtal! (I know, it is extremely rare to find out a broken Xtal...silly me). Changed also the IC responsible of clock generation (the one which is located very close to the SPI).

I'm beginning to suspect about the reformatt suggestion: a damaged PCH. Normally, it takes me as much as a couple of hours (if not less) to fix an A1466. Curiously, when I opened it, this one was immaculate; no signs of liquid, no previous hands over it...a "virgin" machine.
My other suspection was the SMC, because I have no spare for it (other than the one in the working board, but I prefer not to touch it). I reballed the "bad" one a couple of times, and I can swear it's perfectly soldered, in place, no shorts on balls.

Well, maybe I have a brick behind me and my bench, and I don't wanna see it...

Hmmm...does somebody of you know a good place to buy a working board? X-)

OK, I'll keep on working on it. I will return soon with the result of your latests suggestions.

Stay safe!

[fichamba]

Re: MBAir 13” A1466 missing SPI clock

Try this - remove one of the series resistors between the SPI master & SPI slave(s).

Then probe with your scope, the SPI master to see if there is a presence of the SPI CLK upon a power up.

BTW, I have done it. No CLK signal in the scope...

[fichamba]

Re: MBAir 13” A1466 missing SPI clock

Check resistance of L7630 to ground, what is it's value? From experience, under 150 ohms is usually a damaged PCH so results in a brain dead board (generally from liquid damage to PP1V05 converter). IIRC, PCH begins the SPI read, then this passes to CPU.

Also check continuity of traces between resistors from U6100 area to CPU R6110~R6113, R6118, R6119.

Hi reformatt:

Luckily (I hope) resistance between L7630 and GND is higher than 150 ohms. In fact, it is very similar between the 2 boards, the working one and the bad one (around 250 ohms in both cases).





The 238 ohm is the bad,the another reading is the good.

[mon2]

Re: MBAir 13” A1466 missing SPI clock

A1466 are very common units and you can pick them relatively cheap on Ebay.

Just brought in one with SSD + 4GB (wimpy but later want to try to upgrade the ram to 8GB / 16 GB with our BGA rework machine) - 'display is dim'.

Received it and inspected to find (of course), slight liquid damage near the backlight LP8550 WLCSP IC. Attempted to just reflow it but no such luck.

Display can be seen with a flashlight.

Replaced the LP8550 with a fresh device and now have a perfectly working A1466 unit.

This one was $200 USD (with express shipping from the USA to us in Canada).

Logic boards are under $100 on Ebay - just confirm the 820-xxxx # before jumping in.

[fichamba]

Re: MBAir 13” A1466 missing SPI clock

Thank you, thank you, thank you....to all of you.

I'm a kinda stupid or so...in spite of my doctorate in electronics engineering maybe I'm getting old...

You won't believe me if I told you the STUPID thing was happened...just in front of my eyes, and don't see it.

R6130 was soldered vertically, just like R6132. so that means the circuit was open at this point. I saw it, corrected the position of R6130, and...clock present again.

The reason?, simply: I'm an idiot with certificate of origin (and a doctorate, with +40 years of experience designing, etc.). I don't know how to express my gratitude to all of you, and at the same time the shame I'm feeling now.

Anyway, without your kind help it won't be impossible to fix this, mainly because all of you suggested me things that carry me to the error, which, by the way, was caused because in the veeery beginning I removed the SPI just to check it with my SVOD programmer.

I only hope someday I will give you the same in return. I sincerely beg your pardon.

See us here (and a pic of the affected part).

[reformatt]

Re: MBAir 13” A1466 missing SPI clock

All good, we've all done it. At least you spotted it and didn't waste too many more hours on it.

BTW, it's more economical to buy a defective Air on eBay rather than individual spares like motherboards. Often the motherboard faults are relatively simple to repair. If not, you get at least a screen, DC IN board, and trackpad.

Mind you, the last one I just got in looked like someone vomitted on the motherboard. The PCH on that one measured 15 ohms to ground so was a write off. Who knows what else is of use in it after than level of liquid ingress. Win some, you lose some.

[piernov]

Re: MBAir 13” A1466 missing SPI clock

Always disclose full history and troubleshooting steps taken.

[fichamba]

Re: MBAir 13” A1466 missing SPI clock

All good, we've all done it. At least you spotted it and didn't waste too many more hours on it.

BTW, it's more economical to buy a defective Air on eBay rather than individual spares like motherboards. Often the motherboard faults are relatively simple to repair. If not, you get at least a screen, DC IN board, and trackpad.

Mind you, the last one I just got in looked like someone vomitted on the motherboard. The PCH on that one measured 15 ohms to ground so was a write off. Who knows what else is of use in it after than level of liquid ingress. Win some, you lose some.

You're right. But here in Spain things are not so easy as in the US, or Australia.
Hahaaahaaaa!!!, ugly board you obtained!. It's true: with motherboards at hand everything seems easier (look YouTubers Paul Daniels and Louis Rossman). In spite of this, sometimes things become complicated. That was this case.
Thanks!.

[fichamba]

Re: MBAir 13” A1466 missing SPI clock

Always disclose full history and troubleshooting steps taken.

Understood, piernov.
Don't you think I had explained enough?. If so, I can do it better, believe me. And excuse me.

[reformatt]

Re: MBAir 13” A1466 missing SPI clock

Understood, piernov.
Don't you think I had explained enough?. If so, I can do it better, believe me. And excuse me.

Piernov is correct as you didn't mention that you took off U6100. You mentioned that at the very end

Anyway, alls well that ends well.

[fichamba]

Re: MBAir 13” A1466 missing SPI clock

Piernov is correct as you didn't mention that you took off U6100. You mentioned that at the very end

Anyway, alls well that ends well.

Oh, true!. My mistake. Thank you.