I have had the Pi desktop for a couple months. Tonight, I tried to power it up but I have no LED.
Disassembled the boards from the box.
Plugged power into Pi itself and it powers up.
Plugged power into the desktop board and no power to Pi.
Checked voltages around U2 which appears to be a switching regulator. 5.27 volts to pin 4, but L1 has no voltage, which indicates to me the FET in the chip is not switching.
Does anyone have a schematic, or suggestions for repair?
John,
The “wiring” is very simple. The 2400mA power supply was plugged into the desktop board. USB devices plugged in were a keyboard, mouse, camera and an external hard drive. In addition, a display was connected to the HDMI port and a speaker to the A/V port (who also derived power via a USB connection). No SSD drive installed.
I verified that power was getting to the power connector on the desktop board. The volt bus was 0 volts (verified by checking voltage at the Raspberry Pi connector to the desktop board). The fuse on the incoming power is OK, and the incoming power is present on the switching regulator. But there is no voltage on the inductor.
Plugging in the power to the Raspberry Pi board itself works. There is 5V at the connector. I did this without any peripherals plugged in and with the keyboard, mouse and display plugged in to the Raspberry Pi itself. 5 volts was getting to the desktop board as well.
It appears that the switching regulator is not working. I may have overloaded it with all the peripherals plugged into the USB ports. I need a schematic/parts list to figure out what failed and to replace parts. I am quite familiar with switching regulators – I design them into our controller products for the HVAC industry.
Best regards,
Richard Benjamin
Electrical/Software Design Engineer
................................................................................
STULZ Air Technology Systems, Inc.
1572 Tilco Drive
Frederick, MD 21704 U.S.A.
Office: +1 240-529-1266
www.stulz-usa.com
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