Seller Note “NO VISUALS”
- Board itself seems clean, can immediately see a couple of missing capacitors on one of the PCI express lanes.
- Am seeing a very shorted 5v rail (L20).
- Great to have a boardview for this board. Think there may be some innaccuracies though?
- Need to deep dive on U16 (feeds missing 5v rail).
Pre Checks / Multimeter Only
|Test / Checks||Result||Notes|
|1. Visual Inspection Eye / Magnifying Glass||Looks clean. Missing PCI lane capacitors.|
|2. Visual Inspection Microscope||–|
|3. Check for shorts on 12v PCI, 12v PCI-E, 3.3v||OK||Couldn’t find any obvious shorts.|
|4a. Resistance VCore (~0.5)||7.8Ω|
|4b. Resistance VMem (~60Ω)||62.5Ω|
|4c. Resistance 3.3v Rail (~960Ω+)||Ω|
|4d. Resistance 5v Rail (~5KΩ)||<1Ω !!!||In the boardview L20 should be the 5v inductor, resistance appears very low.|
|4e. Resistance 1v PEX Rail (~123Ω+)||120Ω|
|4f. Resistance 12v BUS (14.7kΩ )|
Power On / Test Rig Checks
|Tests / Checks||Result||Notes|
|1. Observations (e.g. PCB heat noticed, |
blank screen, power light on monitor,
bios screen, o/s loaded, artefacts, )
No heat (GPU).
|2. Voltage VCore (~0.88v)||0v|
|3. Voltage VMem (~1.4v)||0v|
|4. Voltage PEX Rail (~1v)||0v|
|5. Voltage 3.3 BUS||–|
|6. Voltage 12 Ext||–|
|7. Voltage 5v Rail||~0.45v|
|8. Voltage VDDCI||v|
|9. Voltage 1.8v||–|
Deep Dive Missing 5v Rail
The 5v rail isn’t completely missing, it is just too low at around 0.52v.
The IC that drives it is U16 (APW7142) 3A, 12V, Synchronous-Rectified Buck Converter (https://datasheetspdf.com/pdf-file/659355/AnpecElectronicsCoropration/APW7142/1).
After removing U16, the short is still there. Need to investigate the connection to U14.
Update 23/05/2022 (A fair amount of experience later…)
A few months later and more cards fixed, I suspected that I may have jumped to the wrong conclusion regarding the U16 buck converter. Instead, the short may be elsewhere. Injecting 0.9v into the 5v rail inductor draws 1.2A. A look with the thermal camera and some touching around reveals one very hot capacitor with a solder bulge near the PEX buck converter (U502).
Removing this capacitor restores the 5v resistance to a much more healthy 3.8K. Now we need to replace that 10uF capacitor and try refitting that U16 buck converter, which may have been removed for nothing. Replacing the APW7142 and the faulty capacitor, yields a working 5v rail and card! 🙂
- MATS passes.
- Kombuster HD runs well.
- Subnautica Below Zero also looks good.
- This card seems a little worn and has 2 replacement fans, but actually runs with good thermals ~26C (low), ~65C (high). Might benefit from a new cooler before selling it.