820-2850 green light no fan spin

[Modder1]

PPBUS_G3H = 8.38
PP3V42_G3H= 3.39
SMC_RESET_L = 3.42
SMC_BC_ACOK= 3.19-3.29 but jumps around there a lot.
I am of course unsure what to do now.
thanks in advance for any help!

 

[dukefawks]

PPBUS should be 12.6V. Corrosion around U7000/current sense resistors.

 

[Modder1]

I already did ultrasonic, and now I flux and heat u7000 but still same. Should I replace u7000? sorry for being such a jerk.

 

[Modder1]

also, the owner says the machine can be turned on by holding option and power for 12 seconds.

 

[dukefawks]

Check sense resistor circuits, R7021/22/51/52 and traces.

 

[Modder1]

R7021/22=16.3 R705/52=8.3 to me it looks like u3301 is missing entirely. not sure if it is supposed to be there on this board. also nothing at j2600
kind regards

 

[jadao]

Hi did you fix it by replacing the resistors?
as the schematic mention 10/10ohms and 0/2.2ohms for 21/22 and 51/52 sensing resistors.

 

[Modder1]

i get beep on 21/22 and 52 but 51 i get 2.4. this mean I should change 7021, 7022, and 7052?
kind regards

 

[Modder1]

are those resistor = to 10K on 7021? sorry I know I am still an idiot

 

[jadao]

7051 at 2.4 ohms is ok
7052, you say beeping, I assume 0 ohm, OK

7021 you say beeping, I assume 0 ohm, NOT OK
7022 you say beeping I assume 0 ohm, NOT OK

7021/7022 NOT OK because schematic shows 10 ohms and you get 0 ohm.

To answer your question, 7021/7022 are not 10k ohms, they are 10 ohms! As per schematic.
10k ohms means 10x1000=10000 ohms.
.
You had before 16.3 and now it beeps...

Check again resistor values of course without power.
Check also traces as asked by Duke

 

[Modder1]

changed 7021/22 with 10K resistor and still same measurement on those. Can't seem to understand where to find equivalent to 7051 on an 820-2530 which is where i pulled the 10K from

 

[Modder1]

oh fuck haha, im so lost, ok let me try to understand and report back

 

[Modder1]

so, is r7021 on 820-2530 10ohm?

 

[Modder1]

also, as far as i can say the traces look fine but again I am an idiot.

 

[Modder1]

ok so, on r7021/7022 i get 10.2 when i have the multimeter in Resistance mode. I was measuring in diode test mode before -fml and 2.4 and 0.2 on 7051 and 7052. but for sure my reading on ppbus_g3h is 8.38 and pp3v42_g3h is 3.42 -does this mean pp4v4w_g3h is present?
I have also got these measurements with the original 10ohm resistors and removed the 10K resistors. I am really sorry guys, I hope you can bear with me.

 

[dukefawks]

You need 12.6V on PPBUS! What is voltage on CHGR_CELL?

 

[Modder1]

3.424 at CHRGR_CELL Duke thanks again for your help!

 

[dukefawks]

Measure between pins 17/18 and 27/28 to ensure the sensing traces are ok. If that is ok then ISL may be bad. PPBUS needs to be 12.6V

 

[Modder1]

between 17/18 and 27/28 on u7000?

 

[Modder1]

17/18 u7000 = 0.03
27/28 u7000 = 0.14
unless I am supposed to be in resistance mode again and in that case between 27/28 u7000 = 20.3
17/18 u7000= 3.13