820-3115 Quarter Fan Spin

brunomotter

Member
Hello! Got an 820-3115 here with quarter fan spin. Already verified all current sensing resistors around ISL area, replaced ISL, replaced clock chip but no luck. I get steady 3.3V on L7220 and steady 12.54V on PPBUS_G3H. Get a sparkle of 5V on L7260 when quarter fan spin. Already verified all traces around ISL and all look good. There was no corrosion at all on this board! I'm lost, because this is the first quarter fan spin that is giving me so much trouble!
 

brunomotter

Member
R7402/3 ok? Any history?
Both read fine! No liquid history... Costumer said it was working and died of a sudden... I think this machine had been worked on before he bought it(he bought it used but working), but cannot be sure because it had no oxidation points nor solder marks on it... The board looked very clean!
 

2informaticos

Administrator
Staff member
Check if all big coils pulse at least.
AL_SYS_PWRGD pulsing?
Also try to start in SMC bypass mode...
 

brunomotter

Member
I do get pulses on all coils except L7510, 7520 and 7550. Cannot start in SMC bypass. ALL_SYS_POWRGD pulses too when quarter fan spin!
 

brunomotter

Member
Check all voltages from pages 71/72.
ENET_SR_LX - pulses when quarter fan to around 2V
PP1V05_SUS_LDO - 1.05V steady
PP1V8_S0_REG - Pulses around 0.4V when quarter fan
PP1V5_S0_REG - Pulses around 2.7V when quarter fan
PP1V05_S0_LDO . Pulses around 0.4V when quarter fan
PP3V3_S4_FET - Pulses to 3.3V when quarter fan spin, around 0.7V when the board shuts down after quarter fan
PP3V3_S3_FET - Pulses to 3.3V when quarter fan, around 0.4V when the board shuts down after quarter fan
PP1V5_S3RS0_FET - Pulses around 3.3V when quarter fan, 0V when the board shuts down
PP3V3_S0_FET - 0V, Pulses to 3.3V when quarter fan
PP3V3_SUS_FET - Steady 3.3V
PP5V_SUS_FET - Steady 5V
PP5V_S0_FET - Pulses around 5V when quarter fan
 

2informaticos

Administrator
Staff member
"PP1V5_S0_REG - Pulses around 2.7V when quarter fan"
Are you sure about this?
Check it again.
Is normal to get lower value, because of short pulse; but not almost two times higher voltage...
If use o-scope, you can catch the real values on all points.
 

brunomotter

Member
"PP1V5_S0_REG - Pulses around 2.7V when quarter fan"
Are you sure about this?
Check it again.
Is normal to get lower value, because of short pulse; but not almost two times higher voltage...
If use o-scope, you can catch the real values on all points.
I will measure it again but I do not have an oscilloscope here unfortunately... That's on my future plans to buy one though...
 

brunomotter

Member
"PP1V5_S0_REG - Pulses around 2.7V when quarter fan"
Are you sure about this?
Check it again.
Is normal to get lower value, because of short pulse; but not almost two times higher voltage...
If use o-scope, you can catch the real values on all points.
I let it read 4 times and it varies from 2.5 to 3V! It's high, but it could be my multimeter trolling me!
 

2informaticos

Administrator
Staff member
Can't be multimeter issue, as the other points do not have same problem.
Remove U7770 and check again.
See if there still pulses the same...

BTW, do NOT quote an entire post; maintain forum aesthetic...
 

2informaticos

Administrator
Staff member
Pufff, really strange; nothing more suspect on that circuit.
Could be PCH/CPU, or just a f***g resistor.
Check 25MHz presence at pin 9/U2600.
Try new BIOS, just in case...
 
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