820-3115-B no power

[Sr. Robot]

Yes, pad 1 remains shorted after removal.

 

[2informaticos]

Remove Q7035 and check again.

 

[Sr. Robot]

Removed Q7035. Short is gone again.

Pin 4 is shorted.

 

[2informaticos]

So you have short to ground at pin 21/U7000?
Then change Q7035 and U7000.
I also recommend to change Q7030 at same time.
Be sure R/C7025 are both good.

Do not resolder F7040, until get correct voltage at C7040.

 

[Sr. Robot]

Pin 21 of U7000 had a bad solder joint, after resolder now we got 0.407 to ground on diode mode.

I replaced Q7030/35 and R/C7025 anyways, also replaced C7045 necause it was looking a bit corroded.

Now i got 0.407 and 0.453 to ground on diode mode on pins 2 and 1 of F7040 (not resoldered yet).

L7030 is also 0.453 diode mode to ground.

However, voltage on C7040 is pulsing between 0.5v and 1.5v

 

[2informaticos]

Post U7000 voltage; pins 1, 2, 3, 9, 12, 13, 14, 15, 17, 19, 20, 27.

 

[Sr. Robot]

2: 17.0v
3: 4.06v
9: 27.8 mv
12: 3.485v
13: 3.449v
14: pulsing between 3.2 and 3.3 v
15: 42mv
17: 1.58v
19: 5.06v
20: 5.07v
27: 1.19v

 

[2informaticos]

Sorry, I forgot to type pin 1 above...

 

[Sr. Robot]

Pin 1: 4.1 mV

 

[2informaticos]

Change Q7085...

 

[Sr. Robot]

Ok now i get pulse between 3 and 4v on C7040

 

[2informaticos]

Post R7020 voltage.

 

[2informaticos]

Post exact resistance between pins 17/18 and 27/28.

 

[Sr. Robot]

Line btween pin 18 and C7050 was blown, soldered a jumper cable.

Now:

pins 17/18 3.3 ohms

Pins 27/28 20.5 ohms

 

[2informaticos]

C7040 voltage now?

 

[Sr. Robot]

No change on C7040 votalge, still pulsing between 3.8 and 4

 

[2informaticos]

Check all solders/traces for U7000 and surrounding components.
Be sure R7012 is good.
Don't forget the R/C networks connected to pins 5, 7, 8.

 

[Sr. Robot]

theres continuity on all pins of U7000. R7012 is 1 kohm

 

[2informaticos]

Get donor board and replace all components in R/C networks from pins 5, 7, 8.
I suppose you cannot properly test the caps...