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820-00928 Strange CD3215 issues

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tcampbell34

Member
Hello. I got this 820-00928 board in that was liquid damaged and has been worked on previously. UB300 and UB400 were replaced and there was still dried flux around them and UB300 was replaced with a CD3215B chip instead of a C00 version. I was getting 5v cycling on 2 ports, nothing on the port for UB300, and surprisingly I was getting 20v 1.5a from the port that corresponds to U3100. When it does take 20v, the fans start spinning on high immediately and the board does not seem to post. No USB activity or caps lock reaction. I found shorts on PP3V3_UPC_TA_LDO, PP5V_S4_T_USBC, and UPC_T_5V_EN. I removed both UB300 and UB400 and all those shorts were gone. Before replacing UB300 and 400, I connected the charger to U3100 again and it was still giving me 20v even with 2 CD3215's missing from the board, which I thought was impossible. I have since replaced UB300 and 400 with new chips but its still the same. Most of the time U3100 will still give me 20v and the other 3 ports will only go to 5v and then cycle on off. Sometimes I will get 5v steady on all 4 ports now also. Do you think I should try and replace U3100 or could this be a SMC issue?
 
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tcampbell34

Member
I replaced U3100 but no change so I replaced the SMC and now I am getting 20v 1.4a on all 4 ports and the fans spin at normal speed now. However, the board is still not posting. I don't get any USB activity or image on screen, but have voltage on CPU vcore.

PM_PCH_SYS_PWROK - 3.3v
PM_PCH_PWROK - 3.3v
ALL_SYS_PWRGD - 3.2v
PM_RSMRST_L - 3.2v
PLT_RST_L - 3.3v
CPU_PWRGD - 0.975
PPVCC_S0_CPU - 1.059
PPVCORE_S0_GPU - 0.9
GPUVCORE_PGOOD - 3.26
GPUVCORE_EN - 3.27
PPVCCIO_S0_CPU - 0.986
PPVCCSA_S0_CPU - 1.118
PP1V2_S3_CPUDDR - 1.19
 
2informaticos

2informaticos

Administrator
Staff member
Liquid spilled board and worked for someone else before, can be a nightmare.

Try known good BIOS.
Check for knocked off components.
 
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tcampbell34

Member
I tried to flash a new BIOS to this but it was failing to erase the chip for some reason. I tried to plug in the charger and now its only taking 20v 40ma, but jumps to 150ma for a second, then back to 40ma. PP3V3_S5 and PP5V_S5 are working and I have S5_PWRGD, but PM_SLP_S5_L is pulsing. All my S4, S3 and S0 rails seems to be pulsing also now. Also PM_SLP_S0_L is 3.3v stable, even though most of the other PM_SLP signals are pulsing. I might just try and solder another BIOS chip from the same model donor board and see what happens.

PM_SLP_SUS_L - 3.3v
PM_SLP_S5_L - pulsing
PM_SLP_S4_L - pulsing
PM_SLP_S3_L - pulsing
PM_SLP_S0_L - 3.3v
 
T

tcampbell34

Member
I replaced the BIOS chip with a new one from the same model donor and tried it as-is and the board is back to where I was before now with 20v 1.4a on all ports and not posting. I tried flashing this chip with a known good BIOS from the same model with a clean me and still the same thing. I cannot find any knocked off components. Most of the visual damage to this board is around U4900, but I don't think anything in this area would be causing this issue.
 
2informaticos

2informaticos

Administrator
Staff member
Disconnect any device from MLB.
Use macOS pendrive with Link LED for test.

Do you note any fluctuation at PPVCC_S0_CPU in the first 10-15s?
 
T

tcampbell34

Member
That is how I am currently testing the board. I do not have anything but the charger ports connected. There is no change in PPVCC_S0_CPU. It comes on at 1v and stays there the whole time and the CPU gets hot. I know the voltage should drop to like 0.6v or something like that, so what would cause the voltage to get stuck at 1v?
 
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