820-4924: Not powering up

[macRepairAmb]

Have this board that doesn't power up, found

PP5V_S0_CPUVR - 1.19v
PP5V_S3 - 5.1v

isolated to both Q7310 and Q7320 to be blow, short between pins 4 and 1,2,3 pins. Resistance reading of about 2ohms. Resistance reading of just pins 1,2,3 to ground is 12ohms, which matches a good board. Replaced both Q7310 after confirm short was gone on pin4 pad's. Once power is applied, both transistors blow out again.

Everything else appears to be measure good, except this two transistors. One thing to note, the transistor package label didn't match the new ones i installed which are both
SISA12DN (new from mouser).

Any suggestions?

 

[2informaticos]

"short between pins 4 and 1,2,3 pins"
This is the way how the driver blocks high-side MOSFETs.
I bet there is no short at all.

For some reason, U7310/20 block Q7310/20.
And this is done shorting G-S pins, inside the drivers.
The short disappears after some time, or repeated measurments in both directions (diode mode).
I never found a shorted G-S MOSFET with good D-S reading!

CPU power supply doesn't work and should find why.
And fixing 5V_S0 problem is the first step.
Check enable signal for U8080, 5VS0_EN.

 

[macRepairAmb]

Ended up being U8005 pulling 5v_s0 close to ground resistance. Now fixed. Thanks for the assist.