Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

[robgerr]

Goodmorning friends of the forum. This laptop has isegent defects:
When I give power on it does not react,
I have to make several attempts until that main power up.
I have no image on both lcd and vga screens.
I noticed that it warms up the pch.
The tensions seem to be there in the coils except that of the cpu (cpu_core) that are missing.
I tried to exchange the cpu but nothing.
I tried to reprogram the bios with dumps found on the net but nothing to do.
I did a reflow on the NVIDIA bga but nothing.
Also changed the ram but nothing
The resistance on coils with inserted cpu and 12 Ohm, I think it is correct.
The thing that leaves me perpplesso and that pch warms up a lot and does not seem normal.
Since I do not have printing on the board it is difficult to follow the diagram but I have measured near the pch of the capacitors and I find a resistance of 3ohm which seems to me low.
I checked on U511 at pin 7 and I find 3V.
Thank you

[caspian]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

It is possible that the PCH is faulty. It is also possible that the CPU-VCore circuit is faulty.
Anyway, you need the schematic of this laptop.

[piernov]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

If it's the PCH and not the GPU, 3 ohms would be too low.

[robgerr]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

I measured the voltage in the capacitors where I find the 3 ohm and when I give the power on I find a voltage of 1.05v in these capacitors

[mcplslg123]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

If you have schematic, Then fiest check VR ON signal is present or not on kbc as well as vcore ic. Next you need to check voltages on all pins of vcore ic.

[robgerr]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

yes I have the scheme. Tomorrow I take note of all the tensions on the IC that produces the vcc core

[robgerr]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

schematic:
https://we.tl/FwkUvd0jE3
U511 -iSL95831AHRTZ-T VOLTAGE:
pin 1 0v
pin 2 0v
pin 3 0v
pin 4 1,05v
pin 5 1,05v
pin 6 1,05v
pin 7 3,11v
pin 8 0v
pin 9 0v
pin 10 1,05v
pin 11 0,67v
pin 12 3,47v
pin 13 3,30v
pin 14 0v
pin 15 0v
pin 16 0v
pin 17 0v
pin 18 0v
pin 19 0v
pin 20 0v
pin 21 0v
pin 22 5,08v
pin 23 19,25v
pin 24 0v
pin 25 4,77v
pin 26 0v
pin 27 0v
pin 28 0v
pin 29 0v
pin 30 5,09 v
pin 31 5,09 v
pin 32 0v
pin 33 0v
pin 34 0v
pin 36 0v
pin 36 4,77v
pin 37 0v
pin 38 0v
pin 39 0v
pin 40 4,82v
pin 41 0,11v
pin 42 3.55v
pin 43 5,09 v
pin 44 0,8v
pin 45 0,v
pin 46 0v
pin 47 0v
pin 48 0v

[caspian]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

replace U511 and Q513 and Q512 and Q515 and Q514 at the same time if you have got spare ones. this may solve the issue. Although I am not sure this will fix the problem, but this is the best work you can do now.

[robgerr]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

thank's caspian

I found iSL95831 instead of iSL95831A but reading on other forums I saw that it worked on this board. Unfortunately I did not have the mosfet, I soldered ISL but still nothing, I do not have the cpu_core

[caspian]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

Now, remove Q513 and Q512 and Q515 and Q514 from the board the test them separately using your multimeter. then while the mosfets are removed, check voltages on all pins of U511. It takes time to reach a successful repair step by step.
have you soldered U511 properly?

[robgerr]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

sorry for my absence with this laptop. I checked the mostet unsolder from the pcb and they are fine. I have re-soldered them in the pcb to avoid confusing the order of how they are soldered since the mainboard has no screen printing

[caspian]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

check whether there is any short on the CPU_Core circuit.

[robgerr]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

ok, check U511 pads for low resistence between pads and ground?

[caspian]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

yes, that is right.

[robgerr]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

u511 resistence (without cpu inserted)
pin 1 inf resistence
pin 2 17.3kohm
pin 3 11.60kohm
pin 4 70ohm
pin 5 80ohm
pin 6 60 ohm
pin 7 3.80kohm
pin 8 11.56kohm
pin 9 30kohm
pin 10 66ohm
pin 11 22kohm
pin 12 14kohm
pin 13 inf resistence
pin 14 10kohm
pin 15 inf resistence
pin 16 25kohm
pin 17 20kohm
pin 18 7kohm
pin 19 100ohm
pin 20 100kohm
pin 21 30kohm
pin 22 150 kohm
pin 23 110kohm
pin 24 5kohm
pin 25 inf ohm
pin 26 20kohm
pin 27 20 kohm
pin 28 1ohm
pin 29 inf resistence
pin 30 170 kohm
pin 31 170 kohm
pin 32 inf resistence
pin 33 1ohm
pin 34 inf reistence
pin 35 70 kohm
pin 36 inf resistence
pin 37 inf reistence
pin 38 inf reistence
pin 39 inf resistence
pin 40 inf resistence
pin 41 inf resistence
pin 42 inf resistence
pin 43 150kohm
pin 44 inf resistence
pin 45 150kohm
pin 46 116kohm
pin 47 inf resistence
pin 48 inf resistence

[caspian]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

they seem fine. how much resistance is at L5 to GND?

[robgerr]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

how much resistance is at L5 to GND?

4ohm

[caspian]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

At this point, I have no good idea about the CPU_Core circuit.
Having 4 Ohms on the 1.05v rail and a hot PCH does not seem good. But I do not know either the PCH, or the GPU, or another component is shorted.

[piernov]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

P1.05V being the core voltage for the PCH, this would point to a bad PCH. Could be another component, so let's check what's on the line.
U525 has P1.05V going in, but also some 3.3V rails so if it was shorted, the 3.3V rails probably should be as well. U525 being bad would prevent the PCH from working, but since it handles RTC clock PCH wouldn't leave S5 state. Could be partially working…
U505 is the LAN controller, they often go bad after lightning strike so this would be a good candidate, but it shouldn't prevent CPU VCore from coming up if it's only partially shorted.
The GPU uses 1.05V only for the PLL, if it was bad and creating a partial short on the 1.05V line, the resistance on GPU VCore would most likely be very low as well. But it's hard to say since it's supposed to be low. Let's say that it may be higher than 8 ohms in normal condition, and lower than 3 ohms if it's bad, but that may not be right.
The CPU, but since it's out of the socket it's excluded.

First check resistance on GPU VCore. Then you could pull U525 and U505 and check if the resistance goes up. If it doesn't, probably PCH. I except the resistance on the PCH core voltage line to be higher than 10 ohms.

[robgerr]

Re: Samsung RV520 (main BA4-01608A Scala2_R) no video and no cpu_core

thank's piernov.
if I try to inject 1.05 volts and see what warms up? So I avoid desoldering components