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Repair guides and support for motherboards and CPUs.

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Beelink SER7 7840HS Motherboard Power Issues

I'm here with a motherboard from a Beelink SER7 7840 HS. The initial problem presented as the computer would randomly turn off while powered from the PSU and with USB PD. More recently the computer turns on but no video or fan spin with either power option.

The motherboard has since been completely removed. All RAM, SSD, WIFI, etc has been removed. Currently being powered with a variable power supply (20V). Confirmed the motherboard still powers up and will turn on via the power button but no video (HDMI or DP) or fan spin. I suspect a short or component failure. I have continuity between the ground test point and most other components and port shielding. No physical damage that I can see. Currently have it powered in a test bed and access to multimeter, soldering, hot air, etc to diagnose. Any help diagnosing this issue would be greatly appreciated.

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Update for anyone reading:

Checked the RTC battery and it has 3.07 VDC. Motherboard powers on (power button LED lights up) but no fan spin or video still. Tested the USB ports and getting approximately 5VDC. Both fan outputs 1.65 VDC. Out of the five pins for the power button (LED) I'm getting 2.67 VDC for one and 3.35 VDC for another.

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Hi @techspec21486

Looking online at images of the motherboard, there's a removable RTC coin cell battery on the motherboard. If this is correct, try a power refresh in case the BIOS has become corrupted preventing a normal start.

Disconnect the power to the motherboard and then remove the coin cell battery from the board and measure its voltage. If it is <2.5V DC or if the battery is >4-5 years old, replace it. It's a CR2032 battery (stamped on battery) and it is available most everywhere e.g. supermarkets

Press and hold the power button for the motherboard (assume it's connected still) for a full 30 seconds and then release it.

Reinsert the coin cell battery (or its replacement) onto the motherboard, (+ve side up as marked on the battery), reconnect the power to the motherboard and check if it turns on with a display etc

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Checked the RTC battery and it has 3.07 VDC. Tried your recommended steps. Motherboard powers on (power button LED lights up) but no fan spin or video still. Tested the USB ports and getting approximately 5VDC. Both fan outputs 1.65 VDC. Out of the five pins for the power button (LED) I'm getting 2.67 VDC for one and 3.35 VDC for another.

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crwdns2933897:0crwdne2933897:0

Hi, sorry to hear that!

Please reach out to our support team at support-pc@bee-link.com — we’ll help you troubleshoot and get things up and running as soon as possible.

Thanks for your patience, and sorry again for the trouble!

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I did reach out and followed the standard email that is sent out to people with this issue. The instructions did not resolve the issue.

Checked the RTC battery and it has 3.07 VDC. Motherboard powers on (power button LED lights up) but no fan spin or video still. Tested the USB ports and getting approximately 5VDC. Both fan outputs 1.65 VDC. Out of the five pins for the power button (LED) I'm getting 2.67 VDC for one and 3.35 VDC for another.

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