Hey,
I've recently sold a PC and (trying to reduce e-waste) told the buyer to bring me his old setup, and I'd take a look at it. Recently I've been trying to repair laptops, mainly, with so-so results.
I'm now looking at an AMD Desktop Kit with no display. Apparently this board reuses (possibly defective) Playstation 5 chips 4700s. It does not provide an internal GPU, or better say in any case it doesn't provide an output for the internal GPU.
There was one obvious fault: One of the caps of the CPU power rail was missing, that happened when the previous owner was changing the CPU-fan and slipped with the screwdriver.
I've since replaced it with another one, although I had to use a THT-one as I couldn't find a fitting SMD variant.
The board does now power on (I think it would have done so before, but I didn't try), but does not give any kind of display. It does not have an onboard speaker (maybe I can install one?) or debug LEDs. Basically, there's no telling what the board is doing at all.
I've checked the power rails: they all measure reasonable to GND, except for the one labeled APU_VDDCR_GFX_RUN. That one measures ~0.3Ohm to GND. I'm confident saying it's basically shorted.
The voltages when powered on are as follows (the board has some testpoints for basically all the bigger voltage rails)
TP_APU_VDDCR_CORE_RUN 0,81V
TP_APU_VDDCR_SOC_RUN 0,85V
TP_APU_VMEMIO_SUS 1,36V
TP_APU_VDDA_RUN 1,8V
TP_MEM_VPP_SUS 1,83V
TP_VDD18_S5 1,82V
TP_1P1_ALW 1,1V
TP_3VSB 3,3V
TP_APU_VDDP_RUN 0,75V
TP_BAT1 3,1V
They all seem normal to me
TP_APU_VDDCR_GFX_RUN 0,83V
Even this one, that seems shorted to GND, get's pulled up to something that is normal imo.
I've since:
- interrupted the rail of APU_VDDCR_GFX_RUN - that drastically reduced the power draw of the APU. Before that, it'd get hot within seconds, now I can touch it even after letting it run for a while
- measured with the scope but have not seen any signal, only DC values of GND / 1,8V / 3,3V,
- on a UART header that is connected to serial out pin (pin 59) of the SuperIO ITE8772E (https://www.inorepair.com/wp-content...T8772E-ITE.pdf)
- no activity at the BIOS-chip
- PIN 6 (ATXPG) and 7 (CPUPG) of the ITE8772E are HIGH
- no activity at the TPM / LPC connector
- done a CMOS reset multiple times - that changed that the CPU fan now is always at 100%. It'd regulate itself before. As far as I remember, that stopped after the first CMOS reset.
- noticed that the FCH is getting burning hot (with its small heat sink installed)
I've tested my GPU (old HD7850) in a different PC. Monitor and GPU are working.
Should I do a bios flash?
There's apparently a way to read out POST codes via the LPC connector (https://github.com/MrGreensWorkshop/...PostCodeReader). I guess there's no point in trying that, though, if I don't see any signals with the scope, though?
I'm at a loss, maybe someone else can think of something.
Kindly, Sepp
I've recently sold a PC and (trying to reduce e-waste) told the buyer to bring me his old setup, and I'd take a look at it. Recently I've been trying to repair laptops, mainly, with so-so results.
I'm now looking at an AMD Desktop Kit with no display. Apparently this board reuses (possibly defective) Playstation 5 chips 4700s. It does not provide an internal GPU, or better say in any case it doesn't provide an output for the internal GPU.
There was one obvious fault: One of the caps of the CPU power rail was missing, that happened when the previous owner was changing the CPU-fan and slipped with the screwdriver.
I've since replaced it with another one, although I had to use a THT-one as I couldn't find a fitting SMD variant.
The board does now power on (I think it would have done so before, but I didn't try), but does not give any kind of display. It does not have an onboard speaker (maybe I can install one?) or debug LEDs. Basically, there's no telling what the board is doing at all.
I've checked the power rails: they all measure reasonable to GND, except for the one labeled APU_VDDCR_GFX_RUN. That one measures ~0.3Ohm to GND. I'm confident saying it's basically shorted.
The voltages when powered on are as follows (the board has some testpoints for basically all the bigger voltage rails)
TP_APU_VDDCR_CORE_RUN 0,81V
TP_APU_VDDCR_SOC_RUN 0,85V
TP_APU_VMEMIO_SUS 1,36V
TP_APU_VDDA_RUN 1,8V
TP_MEM_VPP_SUS 1,83V
TP_VDD18_S5 1,82V
TP_1P1_ALW 1,1V
TP_3VSB 3,3V
TP_APU_VDDP_RUN 0,75V
TP_BAT1 3,1V
They all seem normal to me
TP_APU_VDDCR_GFX_RUN 0,83V
Even this one, that seems shorted to GND, get's pulled up to something that is normal imo.
I've since:
- interrupted the rail of APU_VDDCR_GFX_RUN - that drastically reduced the power draw of the APU. Before that, it'd get hot within seconds, now I can touch it even after letting it run for a while
- measured with the scope but have not seen any signal, only DC values of GND / 1,8V / 3,3V,
- on a UART header that is connected to serial out pin (pin 59) of the SuperIO ITE8772E (https://www.inorepair.com/wp-content...T8772E-ITE.pdf)
- no activity at the BIOS-chip
- PIN 6 (ATXPG) and 7 (CPUPG) of the ITE8772E are HIGH
- no activity at the TPM / LPC connector
- done a CMOS reset multiple times - that changed that the CPU fan now is always at 100%. It'd regulate itself before. As far as I remember, that stopped after the first CMOS reset.
- noticed that the FCH is getting burning hot (with its small heat sink installed)
I've tested my GPU (old HD7850) in a different PC. Monitor and GPU are working.
Should I do a bios flash?
There's apparently a way to read out POST codes via the LPC connector (https://github.com/MrGreensWorkshop/...PostCodeReader). I guess there's no point in trying that, though, if I don't see any signals with the scope, though?
I'm at a loss, maybe someone else can think of something.
Kindly, Sepp