Seller Note “this item does not switch on.”
Summary
- Resistances
- VCore – 0.9Ω (OK)
- Vmem – 22.2Ω Samsung K4G80325FC-HC25
- Display rail – 21.7Ω (OK)
- VDCI – 27.8Ω (OK)
- 5V – 5KΩ+ (OK)
- 1.8v – 3.4KΩ (OK)
- 12v – 6KΩ+ (OK)
- 3.3v – 2.5KΩ (OK)
- Voltages
- 12v – present
- 3.3c -present
- 5v – present
- 1.8v – present
- Display Rail – 0.91V
- VDCI – 0.97V
- VCore & Vmem are missing
Thoughts
- I should investigate the Vmem controller.
- I probed fuse F5 (12V) and there was a spark, possibly it is faulty?
Investigating the display rail
Buck converter GS9238 https://datasheet.lcsc.com/szlcsc/2005191033_GSTEK-Green-Solution-Technology-GS9238-ATQ-R_C532950.pdf
This component is generating an expected voltage of 0.91V
Investigating the VDCI rail
GS7256 http://www.gstekic.com/pdf/GS7256.pdf
Investigating the Vmem rail
The PWM is UP1666Q https://pdf1.alldatasheet.pl/datasheet-pdf/view/1113871/UPI/UP1666Q.html
The required voltages appear to be present
| Pin / Name | Voltage |
|---|---|
| PVCC | 5V (correct) |
| EV | 1.75V (Hopefully this is enough? should be 1.8V?) |
Let’s take a look at the MOSFETS it drives
1 x HGATE AON 6414A https://datasheetspdf.com/pdf/742276/Alpha&OmegaSemiconductors/AON6414A/1
Gate Resistance – MΩ+
2 x LGATE AON 6354 https://datasheetspdf.com/pdf/1306918/Alpha&OmegaSemiconductors/AON6354/1
Gate Resistance 1 – MΩ+
Gate Resistance 2 – MΩ+
I am not seeing any PWM signal on the gates. Maybe that enable signal isn’t high enough? Or possibly the PWM controller is faulty? Since EN on the Vmem PWM is only 1.76V (possibly too low) and my current understanding is that POK on the Display Rail PWM provides this voltage (reads 2.07V), then perhaps there is a resistor that has changed value?