LA-9104P 7 beeps no video (inspiron 3521)

[cpt.charlie]

Hi folks, happy new year!

I'm trying to fix this dell that turns on but it gives no display, just 7 beeps (CPU related code), visual inspection didn't reveal anything significant, after some measures i discovered that the board is generating all voltages except +VCC_CORE and VCC_GFXCORE_AXG this voltages are generated by the same IC PU700 checked the IC and VR_ON is high and the chip gets proper 5V power.

I thought the chip was defective and replaced it, to my surprise i got the same result with the new chip oops! checked the mosfets and seem OK, the resistance on the coils is about 4.3 ohm, then i checked the control signals comming from the processor VR_SVID_CLK, VR_SVID_ALRT#, VR_SVID_DAT all the signals are at 1.05v but no data transmission on the lines just steady voltage, for some reason the CPU is not sending the control commands, just in case i reflashed the bios chips (but not the EC as i don't have a suitable programmer) and nothing changed. PLT_RST# remains at low value but this signal can be controlled by EC and PCH, any idea for a proper diagnose without having to replace these chips?

Thanks in advance.

[mon2]

Re: LA-9104P 7 beeps no video (inspiron 3521)

https://www.youtube.com/watch?v=q5LpXlSeDxA

[cpt.charlie]

Re: LA-9104P 7 beeps no video (inspiron 3521)

https://www.youtube.com/watch?v=q5LpXlSeDxA

Hi nom2, in my case 1.5v is present and the mosfet works just fine, my problem seems to be a bit more tricky.

[mcplslg123]

Re: LA-9104P 7 beeps no video (inspiron 3521)

Are you getting 1.8V at PL400?Next check PU500,Pin1 & PU600,pin4 for powergood signal. Remember, this mb has PG from one ic as enable for the other Like PG of pu500 enables PU600 and so on. So just check all the powergood and you will be able to solve the problem. I've repaired more then 30 boards of LA-9104P for 7 beeps. the reason are always not same but basics remain same. Another thing to watch is 1.5V at UZ1.

[cpt.charlie]

Re: LA-9104P 7 beeps no video (inspiron 3521)

Are you getting 1.8V at PL400?Next check PU500,Pin1 & PU600,pin4 for powergood signal. Remember, this mb has PG from one ic as enable for the other Like PG of pu500 enables PU600 and so on. So just check all the powergood and you will be able to solve the problem. I've repaired more then 30 boards of LA-9104P for 7 beeps. the reason are always not same but basics remain same. Another thing to watch is 1.5V at UZ1.

Hi, i've checked all the power supplies and except PU700 all PSU are working fine.

PU200 (3.3v and 5v) OK --> Pgood pin 23 =5V
PU300 (1.5v and 0.75v) OK --> Pgood pin 10 =0V not connected
PU400 (1.8v) OK --> Pgood pin 4 =0.5V not connected
PU500 (1.05v) OK --> Pgood pin 1 =3.3V
PU600 (0.9v) OK --> Pgood pin 4 =3.3V

UZ1 also works fine.

[Spider1211]

Re: LA-9104P 7 beeps no video (inspiron 3521)

Try a known good BIOS. I had a similar issue once, 7 beeps and everything else seemed OK. Flashing a known good BIOS worked for me.

[cpt.charlie]

Re: LA-9104P 7 beeps no video (inspiron 3521)

I have tested 2 bios with the same result, unfortunately i can't flash the EC.

[mcplslg123]

Re: LA-9104P 7 beeps no video (inspiron 3521)

Do you have a dc power supply? If yes, then what is the consumption on your dc supply
01. With ram
02. Without ram

DRAMRST# present on pin30 of ram slot??

[cpt.charlie]

Re: LA-9104P 7 beeps no video (inspiron 3521)

Hi mcplslg123, the current consuption with ram (and no fan) is 122mA with peaks of 135mA, without ram it remains at 119mA, pin 30 on both cases is 0.34V, i've checked QC2 and all i get is 3.3v on gate and 0V on drain and source, however none of these lines are shorted to ground, RC108 and RC110 are 1K and i have the expected 1.5v at RC108.

[mcplslg123]

Re: LA-9104P 7 beeps no video (inspiron 3521)

Current consumption at 122mA indicates a lot of rails are not coming up. So do check which coils are having no voltages and post here.Check all dc-dc transfet like QZ1/3/7 and UZ1(Page35 of schematic). Measure voltage at PIN1/4/5 of all these 4 mosfets (mb turned on) and post it here.

[cpt.charlie]

Re: LA-9104P 7 beeps no video (inspiron 3521)

In fact the only missing voltages are +VCC_CORE and VCC_GFXCORE_AXG i no longer have the board as i returned it to it's owner, the low current i think it's caused becouse the chips were in reset state, thaks everyone for the help.

[mcplslg123]

Re: LA-9104P 7 beeps no video (inspiron 3521)

Often the cause of low consumption on this mb is QZ3 which transfer less then 3.3V to PCH. Anyway , no point discussing it since mb is no more with you.