A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

[Stiffmesiter]

Hello,

I have a A2159 stuck at 5.16 V and 0.01 A on the amp meter. I should note that this will be my first 'real' fix, and have really caught the learning bug for logic board repair. I am really excited to hear what this forum has to say and help round out my understanding. With that being said, I have slowly been working on it over the holidays and acquiring the tools to fix it, but have not done anything substantial yet besides ultrasonic cleaning the board.

Here is the pre-req information:

History, symptoms, and state-of-the-machine...

Person said that it just stopped working. They had powered it off at work, and then it would not start back up at home a couple days later. They tried multiple power cables and it would not turn on. They mentioned no liquid damage, but upon inspecting the board, I found traces of coffee stains, most notably around the J1800 connector, but otherwise, a clean board. I cleaned those areas with ISO and did and ultrasonic cleaning as well. The board input readings remained the same post cleaning.

Measurements

PPBUS_G3H = 12.3 V @ Pin 2 on F7000

PP3V3_G3H = 0 V @ Pin 1 on C7612

PP3V3_G3H_RTC = 0 V @ Pin 1 on C3100

PPBUS_HS_CPU = 12.3 V @ Pin 1 on C7752

PPDCIN_G3H = 5.16 V @ Pin 1 of F3001 (same as amp meter)

PP5V_G3S = 0 V @ Pin 1 of C7671

PPVIN_G3H_P5VG3S = 12.3 V @ Pin 1 of C7660

PPVIN_G3H_P3V3G3H = 12.3 V @ Pin 1 of C7687

PPVIN_G3H_P3V3G3HRTC = 12.3 V @ Pin 1 of R6900


Any help is greatly appreciated. Thanks in advance!

[mon2]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

Welcome to the forum. Your posted voltage list is excellent and helps to get started.

1) Review the power sequence of the power rails for this logic board. Each must follow in order (sequence) to power up the logic board.

A partial is attached. You have PPBUS_G3H which starts up in a BOOST mode.

That is, your external power adapter is only supply 5 volts (not the desired 20v) and yet PPBUS_G3H is @ 12v3. This is because the ISL (Intersil / Renesas) IC @ U7000 is capable of operating in BUCK / BOOST modes.

Buck mode will accept a higher input voltage and output a lower voltage.

Boost mode is lower input and higher output voltage. Boost mode is always wimpy on the amount of current that can be supported.

You will have 20V negotiated by the ACE controllers (CD3215 / CD3217, etc.) only if all the power rails to power each power delivery controller are present.

Specifically, you are missing PP3V3_G3H_RTC and is halting the 20V power delivery negotiation. That is, your logic board is able to work with intelligent power adapters. These are the USB Type C style. The external power adapter is able to spit out a mix of power delivery contracts (voltage & current as a paired value). Only if the ACE controller on the logic board is working (each one must be ok) -> then the ACE controller will extract the database of supported PD contracts and dial up the best one to power the board.

You are presently in the default 5 volt mode due to the missing power rail. Fault may be elsewhere but this power rail is still necessary to move forward.

You will need to review U6903 IC which is the creator of this missing power rail.

Inspect for possible damage in the region. You DO have voltage going into this IC. Confirm that the EN pin is a logic HIGH to enable this power rail.

What is the voltage to ground of the EN pin of U6903 ?

Meter in DC volts mode -> 20 v or higher is ok.

Red probe @ R6907; Black probe to ground. Check the voltage on each side of R6907.

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

@mon2 - Thanks for reaching out. I have obviously read a bunch of your responses on this forum and I really appreciate having the support from a vet like you. Thanks for awesome and clear response, it was really helpful in pointing me in the right direction.

Attached is a picture of the chip with no glaring issues.

As per requested, I measured 5.097 V @ Pin 1 & 2 on R6907.

To be a little proactive, I also measured:

- 12.3 V @ Pin 1 & 2 on R6900
- 12.3 V @ Pin 1 on C6909
- 0V @ Pin 1 on L6900

Based on this, I assume it means that U6903 is defective?

[xtcfreak]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

I don't have any help to offer as I am still learning. Without going thru a lot of posts on this forum yet, I can with 100% certainty say mon2 posted a response that could be a perfect example of how it should be done.

Anyone looking to actually learn will be spending a lot of time following mon2.

mon2, do you have any written guides or books that you have written or can recommend? All those youtubers keep recycling the same old info but not one has mentioned the key info that makes it all clear like you did.

Thank you

[mon2]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

xtcfreak - thanks for the kind words from a fellow Canadian. Just paying it forward. Had some lucky breaks early in life from mentors who answered questions about electronics when I was confused reading Popular Electronics articles. One was an employee (college student while I was a teen) of the former Radio Shack store who was a great teacher - his boss wanted me gone and asked me to stop visiting their store. Learned a great deal in that summer, have been running a design company for many years now to supply major OEMs (Apple was one of them; Dell / HP / Foxconn are house accounts) and trying to help the next generation where possible. So many stories to tell but this is not the forum nor the time. One quick one is how for the longest time, we (my brothers and family) were being flagged constantly at the US border crossing. Consumed an hour or so every time. Senior official asked what I do for a living..told him the truth, supply their Homeland Security and their Dept. of Defense. No more issues after that day.

There are some great teachers here so don't stop reading and learning.

Do read the above stickies from @Piernov and others. Logiwiki / Repairwiki / the power up states from the repair shop in Australia, etc. - excellent websites.

No books that I have written (yet) but working on some pending tools for this industry. But it is a back burner project on top of the normal workload. This forum is a form of a stress release from the normal chaos. More details to follow once we finish the design.

Back OT...

@Stiffmesiter, remove all power -> meter in resistance mode and confirm that there is no short on PP3V3_G3H_RTC.

What is the resistance to ground of L6900 (coil) ? If the resistance is not too low, then U6903 is considered to be defective.

Post the resistance reading.

You have Vin, you have the enable pin but no output. It is possible for the regulator to shutdown if the feedback loop (FB) is broken. Do confirm this region.

This part appears to be available from Digikey

https://www.digikey.ca/en/products/d...80YZFR/6572502

Ti webpage on the same:

https://www.ti.com/product/TPS62180

Do note that this part is a BGA device. Respectively, it will be a bit of a challenge to service if you are not yet comfortable with the replacement. Suggest to test and learn the process with dead donor boards from Ebay, etc.

Lots of flux, tweezers, hot air with low air pressure so the parts do not go flying into the next state & patience. When the part has the underside BGA balls in liquid state, a gentle nudge of the tweezers will be able to move the part.

Then carefully remove the part off the board - not sooner else you can rip off the PCB pads = game over for the repair.

Do review the many videos on this subject. Alex @ Northridge Repair is a great teacher and you can also watch Ben and his tristar repair videos.

If in doubt, just ask and someone will reply with advice.

From the details so far, it appears that U6903 is defective and halting your boot up process.

Would you have hot air tools?

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

@xtcfreak - I completely agree and thanks for jumping in. After mon2's first response I made a reminder in my notes to ask the same thing. I have so many questions and there is so much domain knowledge to infer.

@mon2

In diode mode, the resistance of L6900 is 0.69 MOhm (Mega!?! does that unit my multimeter is spitting out make sense? Is it that large?).

I am not entirely sure what you mean by this: "It is possible for the regulator to shutdown if the feedback loop (FB) is broken. Do confirm this region.". How would I go about this?

In any case, it is probable that there is no short and I will proceed replace U6903.

Here we go!

In prep for this, I did purchase a hot-air station and have been watching videos/practicing taking on and off caps from an old laptop. I will start practicing on BGA chips .

Thanks for the links. I will purchase it now.

Also, thanks again for all the help!

[mon2]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

I am not entirely sure what you mean by this: "It is possible for the regulator to shutdown if the feedback loop (FB) is broken. Do confirm this region.". How would I go about this?

On the FB pin of this regulator are some resistors. With no power, meter in resistance mode, check the resistance across each resistor and compare their value against the schematic. The FB (feedback) pin is used to gauge the output voltage is as designed by the engineer.

For the resistance checks, use the resistance mode of your meter. It will have the greek OMEGA symbol.

Then one probe on the coil, other meter probe to ground.

Post the reading or picture of the meter face while taking this measurement.

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

@mon2

Alright, so I bought two chips and they came in today. I practiced on an old laptop I hard around, but not going to lie, the chip placement and size of U6903 really made me punch above my weight on this one. I could use some spot checking on how I did (I am writing this reply while the board is in the ultrasonic cleaner, so I haven't tested the results yet, fyi).

In a recap, I followed this video by Louis as a primer (https://www.youtube.com/watch?v=btEk...-UpFULLQUALITY). I have probably watched 25 times since we last spoke (in addition to a bunch of northridge's videos - what a great channel recco).

I was able to get the original chip off with no broken pads. Thinned the pads and then tried wicking. Wicking was hard and did not go to plan. So I ended up just removing the excess solder with my iron and getting the grid as clean/flat as possible. I got the first replacement chip #1 on the board but there was no change on the amp meter. Re-probed L6900 and no change on output. Re-probed R6900 and C6909, again no chnage and a bit of a sigh of relief as I was terrified I destroyed surrounding components. Based on these reading, I made the conclusion that I did not get a good seat of the chip - but no worries, I bought another, and was now more 'skilled' (/sarcasm). Additionally, I was going to document things more appropriately in prep for this post!

So we begin on replacement chip #2. Chip #1 came off without a hitch (see 2nd_lift.png). I re-thinned and then cleaned with iso (see 2nd_lift_iso.png). To me it looked decent, but please correct me if I am wrong. I also took a pic of the bottom of chip #1 (2nd_chip.png), and I am seeing many balls that did not make contact - again correct me if I am wrong. I also don't see an signs of bridging, so that made me feel better. I then did another ultra sonic cleaning prior to chip #2 placement. Once clean and bathed in iso, I re-fluxed and seated replacement chip #2 with the intention that I was going to hit it with heat longer and do a little more nudging try and ensure connectivity - see (2nd_Chip_place_v1.png).

The results look alright to me, but again, I am a noob and could use some experienced eyes.

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

Ok, so post replacement update. I think it worked, since amp meter is showing different results, which I consider progress.

New state:

Amp meter: 5.12 V at 0.19A

PPBUS_G3H = 12.3 V @ Pin 2 on F7000 (same)

PP3V3_G3H = 0 V @ Pin 1 on C7612 (same)

PP3V3_G3H_RTC = 0.5 V @ Pin 1 on C3100 (different)

U6903 readings:
- 12.25 V @ Pin 1 & 2 on R6900 (same)
- 12.25 V @ Pin 1 on C6909 (same)
- 0.45 V @ Pin 1 on L6900 (different)

So what does this mean? I now have current coming out of U6903, but not what is expected (e.g. 3.3)...

Also note, resistance readings on Pins 1 & 2 of bot L6900 and L6901 are 1.45 ohm.

[mon2]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

Amp meter: 5.12 V at 0.19A

Power delivery meter is @ 5 volts. To achieve the 20v contract, each of the ACE controllers must be working.

Review the LDO voltage rails for each such CD3217 ACE controller (U3100/U3200).

Post each voltage reading to ground.

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

Understood.

Here are the attached readings:

U3100:

PP3V3_UPC_XA_LDO: 3.34 V @ Pin 1 on C3108
PP1V5_UPC_XA_LDO_CORE: 1.58 V @ Pin 1 on C3105

U3200:

PP3V3_UPC_XA_LDO: 1.26 V @ Pin 1 on C3208 *
PP1V5_UPC_XA_LDO_CORE: 0 V @ Pin 1 on C3205 **

I assume this mean U3200 needs to be replaced?

If I can ask an explanatory question: Why/how did you jump from U6903 to the USB controllers? From the values I posted, I would have assumed U6903 was still the issue, as it is still not generating a 3.3 V output.

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

Bump on this thread. Any help is appreciated

[mon2]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

Move the power adapter to the side controlled by U3200. Measure the LDO voltage rails again of U3200.

Post each measurement.

Both ACE (CD321x) controllers must be present and working to negotiate the 20v power delivery contract.

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

Right. Silly mistake

Moved the power to the other port and re-measured U3200. Updated readings are:

PP3V3_UPC_XA_LDO: 3.43 V @ Pin 1 on C3208
PP1V5_UPC_XA_LDO_CORE: 1.58 V @ Pin 1 on C3205

[mon2]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

What is the voltage to ground at C6912?

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

0 V @ Pin 1

[mon2]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

Measure the voltage to ground of:

R6900, pin #2 (PPVIN_G3H_P3V3G3HRTC_R)
R6907, pin # 2 (CHGR_EN_MVR_R)

After the above, remove all power -> meter in resistance mode.

Measure the RESISTANCE to ground of C6912, pin # 1 (PP3V3_G3H_RTC_REG_R)

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

R6900, pin #2 (PPVIN_G3H_P3V3G3HRTC_R): 12.25 V
R6907, pin # 2 (CHGR_EN_MVR_R): 5.07 V
C6912, pin # 1 (PP3V3_G3H_RTC_REG_R): 1.4 ohms

[mon2]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

C6912, pin # 1 (PP3V3_G3H_RTC_REG_R): 1.4 ohms

You have a shorted part on this line.

The voltages are fine on the INPUT to this regulator @ U6903 and the ENABLE voltage is also requesting for this part to turn ON. The ultra low resistance is causing this regulator to turn OFF due to an excessive current draw = too much of a load for the design of this power rail.

See attached.

Remove the 2 x highlighted resistors on the output side of this rail.

After doing so with NO power -> measure the resistance to ground of:

R6934 or R6935 - pin # 1. Either is ok.

Is the low resistance still present ? Post the measurement.

Then check R6934 or R5935, pin # 2. Either is ok.

What is the resistance to ground ?

By removing these 2 resistors, you are isolating the power rail to home in on the shorted part(s).

BTW - Would you have an adjustable power supply ? Thermal camera or alcohol? Costco stuff works well.

[Stiffmesiter]

Re: A2159 - 820-01598 - Stuck at 5V and am a beginner looking to learn

Ok, removed R6934 and R6935

R6934/6935 @ pin 1: 1.85 Ohms
R6934/6935 @ pin 2: 390 kOhms

Ahhhh, makes sense. I guess from these readings, it suggests that the short is further downstream?

I have 99.9% isa. I will amazon a power supply now.