Apple 820-2327-A PP3V42_G3H Low

[chabregas2k]

Hi everybody. Ive been self learning on the electronics bit, and got away with a bunch of repairs actually, but the time has come where im running in circles and would love some help and knowledge with this.

So here it goes.

MB 820-2327-A

PPBUS_G3H - 12.61v
PP3V42_G3H - 3.01v (for reference, on pin 2 of L6995 - Pin 1 is 3.42v)

Charger light is solid green. Any pointers to where i should start looking? thanks a million. Ill leave you with the bv and schem im using.

Toni

[mon2]

Re: Apple 820-2327-A PP3V42_G3H Low

Pin 1 of L6995 = 3v01 but Pin 2 of L6995 = 3v42 ?

1) check soldering joints on L6995

2) power down, meter in ohms mode. Resistance to ground on Pin 2 of L6995? You may have a shorted cap downstream on this rail.

3) Confirm the resistors are of the proper value @ R6995 & R6996 = feedback resistors for U6990.

If Pin 2 of L6995 = 3v42 but lower elsewhere for the same rail...

check for damaged traces between Pin 2 of L6995 and the contact @ 3v01.

check this rail without a battery / keyboard / trackpad connected

If 100% sure the connections are direct between these 2 points, you can attempt to bridge the 2 locations using wire-wrap / thin wire. This voltage rail is of relatively low current (200mA) so wire-wrap / jumper wire should be ok to use but the root cause should be first explored.

[chabregas2k]

Re: Apple 820-2327-A PP3V42_G3H Low

Thanks a lot for your time.
First off, sorry if i didnt explain properly:
L6995 Pin 1 3.42v (p3v42g3h_sw)
L6995 Pin 2 3.01v (pp3v42_g3h).

As for your pointers:
1) check soldering joints on L6995
removed, resetted. Same values

2) power down, meter in ohms mode. Resistance to ground on Pin 2 of L6995? You may have a shorted cap downstream on this rail.
51.2kohm

3) Confirm the resistors are of the proper value @ R6995 & R6996 = feedback resistors for U6990.
R6995 141kohm - R6996 120kohm (Both lower than schematic)
Measured onboard yes?

All traces okey.

for reference, U6990:
Pin 5 - 3.42v (P3V42G3H_SW)
Pin 6 - 6.5v (P3V42G3H_BOOST)

Thanks a million.
Toni

[chabregas2k]

Re: Apple 820-2327-A PP3V42_G3H Low

Should i remove C6994 and test outside? both 6.5v and 3.42v lead to that capacitor. that capacitor is right before pin 1 of the coil (L6995), where it only gets 3.42v. is it supposed to be like this?
Sorry again. Just me trying to work out the logic without the proper knowledge

[Harryrepair]

Re: Apple 820-2327-A PP3V42_G3H Low

Hey ,
i am new to this as well, but like to figure out with you.

PIN1 seems to be ok, you should have a look behind the coil on pin 2 and following, isn`t?
Have a look at C6999.

[Harryrepair]

Re: Apple 820-2327-A PP3V42_G3H Low

I would solder out R6995 and R6996 and measure them. If still the same, i would exchange them.

[mon2]

Re: Apple 820-2327-A PP3V42_G3H Low

1) C6994 is a 6v3 rated capacitor. This means the capacitor is capable of being used in a circuit up to 6v3 without damage to this component. The part does not have to operate at this voltage but can do so, if required without damage. There are articles on the net (started with an engineer @ Maxim Semiconductor that blew the whistle on the cap industry on how if the cap is not operated at the rated voltage (or close to; also physical cap size matters) then the capacitance de-rates. However, that is another topic and not your issue of this rail not working.

https://www.maximintegrated.com/en/d...ls/5/5527.html

2) Most likely C6994 is ok since you are measuring 3v42 at that junction.

3) Double check these voltages again to be sure the rail is indeed not equal to 3v42 (or very close to this value).

4) Good idea as noted above to carefully remove the FB (feedback) resistors out of circuit - you can slide each with a hot air tool onto one leg and take their measurements. DO NOT, repeat DO NOT power up without these parts back onto the circuit. Without these FB resistors in place, the downstream voltage can spike to beyond 3v42 and cause some serious damage.

5) The parts are very small (0201) so recommend low hot air pressure but of course enough heat to melt their solder joints. If the parts are not correct as they appear to be, best to order a strip of them from Arrow or similar. Very inexpensive and should be < $ 1 USD for 25-50 of each.

6) Using the supplied formula, Vout will not be 3v42 if the resistors are as reported on your logic board.

Vout = 1.25V * (1 + Ra / Rb)

Vout is fine with the Apple supplied FB values for each.

[dellxps15]

Re: Apple 820-2327-A PP3V42_G3H Low

i would remove l6995, inject 3.42 volt with lab psu on pin 2 and see how much power it drain....

[chabregas2k]

Re: Apple 820-2327-A PP3V42_G3H Low

i would remove l6995, inject 3.42 volt with lab psu on pin 2 and see how much power it drain....

How much amps should it go with?
Sorry in advance for the stupid question. better safe than sorry

Toni

[dellxps15]

Re: Apple 820-2327-A PP3V42_G3H Low

How much amps should it go with?
Sorry in advance for the stupid question. better safe than sorry

Toni

on my lab psu i cant setup the ampere. i can chose only low ( max 1A) or high (5A). iths then the lab psu that give the consumption led to see when something is shorting or not with a green light becoming red. i start with low voltage like 1 volt and increase it (till the max voltage rail im investigating). for example on that case ill go from 1 volt to 3.3 volt if nothing is getting hot and psu doesnt drain much power.

voltage and ampere also dipend from what is shorted. if its a small 0402 capacitor then it will probably drain only 5-6 watt, but if its bga it can easly drain 15 watt or more to get very hot, but in that scenario, for example cpu... i use max 1.5 volt to check if cpu is getting even a bit hot then its shorted.

now 3.42 volt is not used as main power rail for ic or bga, but as a enable or comunicate signal voltage, so if something is shorted there it would probably mean that some very small ocmponent is in short and just 1-2 volts are enought to understand where the short is .

to be precise, check the ampere it is taking whlile injecting voltage. from 1 volt u can just easly see if something is wrong.
example: if with 1 volt u have 0.005 A use... u can raise that volt to 2 volt and see if it still is some 010A or so.... (in that case i would say no short present). if with 1 volt is is already taking some good amount of ampere, i would check also motherboard for getting hot....
with 1 volt inject i would left power for 20 second, then power off psu and check if something on the board is more hot then other part... if nothing is hotter i continue investigating with other 20 seconds and check again... then increase a bit voltage again 20 seconds and check fot hot spot.

edit: u have a drain of 0.5 volt on ur rail. so it is already taking 2.5 watt or so. start with 1 volt and do what i have write here.