No 5v_s0 00165

[Rford]

Having some issue isolating an issue on 5v_s0. No liquid damage, no visible damage. Sent to me, orange light, no boot. Opened it up, no fan, tested no 5v_s0. 3v3_s5 present. Any ideas. Tried a monkey see monkey do at u7200 and changed it. No s0 at pin 16, ppvin_s0_cpuvr_vin=8.56v. There looked to be some discoloration around the chip, so that's what prompted me to switch it out. No such luck. Ideas?

 

[dukefawks]

Why are you checking S0 when there probably is not even S3?

Check for pulse on L7520 when connecting power. Check all rails for shorts.

 

[Rford]

There is no pulse at L7520, this is assuming my scope is set right... There is not short on that rail either. It looks like, it has a direct line from the connector to the io to L7520... Nothing there either.

 

[Rford]

Also, is it not pertinent to go in the order of which they are listed on the schematic, as they will not be present without the rail prior? dukefawks

 

[Punkedthis]

Always go in order from
G3H RAIL or pp3v42_g3h
PPBUS_G3H
Rtc rail
5v rail, s5, s3, s0
3v rail, s5, s4, s3, s0
And so on..at least I did..

 

[Rford]

Any idea what could cause s3 not to be present? No shorts on circuit. Struggling to determine, why it isn't coming from the connector in the first place. Is it because of IO board (unlikely) or is it because of another component up stream?

 

[dukefawks]

Was this a liquid damaged board? RTC voltages present on R1300/1/2/3?

 

[Rford]

yes there is voltage on all, and resistance checks out. It seems as thought it was liquid damaged, but the shop before me US cleaned it... They dont mess with the board beyond that though.

 

[dukefawks]

Where was the liquid? Check U6100 area, U1950 pin 8 clock chip. Check shorts to GND on all coils. Check for power cycling again on L7520