G4 Cube VRM

[RickM]

According to the specs the LTC7819 has a maximum output voltage of 0.8 Volt to 99% of the input voltage Vin (4.5 - 40 Volt). So I consider 12 Volt not " high voltage". = 12 / 0,99*40 = about 30% of max.

 

[jasperman]

Any suggestions for the best way to test an original VRM board? I have two replacements now for my “magic smoke” VRM I posted a bit ago. Should I look for shorts on the connector voltage pins in case there is a short on the motherboard? Or any way to test a board in isolation? I’d rather not plug it in and just hope for the best. Thanks everyone.

 

[JDW]

Unfortunately, I don't have a schematic of the VRM to know which pins are what. Knowing that is very important if one wishes to test the VRM outside the Cube. But you're right, it does make good sense to test it outside the Cube if you are able to find out how to properly identify the voltage and ground INPUTS and then identify the OUTPUTs.

 

[jasperman]

Thanks for the reply JDW. I believe evanboonie's start of a VRM replacement has the pinouts for the connector but need to reinstall Kicad to check.

 

[François]

View of the DC-DC board's connector with the plug holes facing towards you. A1 is in the top left corner of the drawing.

__A1_________connector___________ | 2 0 0 3 3 3 3 0 0 0 0 5 5 0 1 | | 2 2 0 3 3 3 0 0 0 0 5 5 5 0 e | ================PCB===========B15

Legend:
0: GND
1: 12V
2: 28V
3: 3.3V
5: 5V
e: enable

 

[jasperman]

Look for a replacement for my blown C3. It looks to be a 150 uF 6.3v capacitor? Does anyone have a digikey/mouser/newark link for the proper replacement?

Tested out my blown VRM and the 5v rail is shorted. Not sure which MOSFET is bad since they are in shorted with a DMM. Hopefully it didn't nuke my motherboard or some other component.

Thank you!

 

[jasperman]

someone on Reddit answered my question:

Panasonic TPB Series 150uF 6.3V Polymer Capacitor:

https://docs.rs-online.com/4155/0900766b814dbdb1.pdf

Kemet PS/K Series Neocapacitor, jE8 = 150uF 6.3V:

https://web.archive.org/web/2018012...uctCatalog/Attachments/728/neocapacitor_e.pdf