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Mini PC with dead motherboard. How to troubleshoot and repair?

So... I recently purchased this Minisforum Mini PC for what seemed like a reasonable price on eBay. Unfortunately, when it arrived, it wouldn't power on. I opened it up, and discovered that there was no RAM or SSD installed. Thinking that was why it wouldn't power on, I managed to get a partial refund from the seller, and purchased replacements. When the new RAM and SSD arrived, I installed them, and tried powering it on again. It was still dead. And apparently, when I accepted the partial refund, I finalized the order and forwent any possibility of performing a return, so returning it is no longer an option.

After doing some research, (which I probably should've done before buying it 🤦‍♂️) I discovered that there have been several reports of these things dying randomly. The only sign of life is that when it's plugged into to power and Ethernet, the Ethernet lights blink.

I've tried different combinations of holding down the power button and clear CMOS button for varying amounts of time, but with no success. I also installed the SSD in another machine and confirmed that it was functional. I don't have a machine that takes DDR5 SODIMMs, so I haven't been able to test those, but I have no reason to believe that they are faulty, considering what I've heard about this model, and the fact that it does the exact same thing (nothing) with and without the RAM installed. I have tried using just one RAM stick and swapping the single stick between the two slots, but that didn't do anything. USB devices don't appear to receive any power. The power light doesn't come on at all.

In some of the complaints posted online, the two components marked on the picture below literally fried themselves. I wasn't able to find any burnt out components on the motherboard, but would it be possible that they are still faulty?

Anyways, that brings me to my question: How would I go about troubleshooting this thing? And once I find out what's wrong, what equipment would I need to repair it? I have a multimeter that I know how to use, and I'm competent with working on computers. I also repaired a motherboard with faulty capacitors once, but those were through-hole, so I understand the procedure and equipment for replacing surface mounted components will be different. I also understand that this will be very difficult, and require a lot of effort to repair, so please understand that while I would like to have this thing be functional, I also would like to learn how to perform board-level repairs on computers. I'm viewing this as a learning opportunity as much as anything else, so please don't just tell me it'll be too hard and that I shouldn't bother trying. I'm willing to invest the time and effort into getting this thing running again.

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@fixer85785 those two are TPC8031-H(TE12LQM) MOSFET N-CH 30V 11A in a 8-SOP (5.5x6.0) package. Yes, those love to go on the fritz in this model and are most commonly because of secondary errors. Check for short to ground and check for the voltage on the Gate (~25V) of those MOSFETs. Here is a bit of information on Mosfets Prod Guide

This particular series of MOSFET is considered obsolete and thus not available at the place where I get some of my components from (Digikey.com) but you can most certainly find similar there as well.

You need a hot air station, plenty of flux, a steady hand and Eagle eyes (oh yes, plenty of practice too ;-)

To check some more parts on your boards, we would need a picture that shows a better close up. Remember, we really have to zoom in to identify what is going there. Less blue mat and more board will be perfect:-)

Nobody is ever going to tell you that "so please don't just tell me it'll be too hard and that I shouldn't bother trying" on here. It will always be up to you as how far you want to go. It will always be your call, not ours. We want you to be empowered and provide as much help and advice as we can give, but even that is sometimes not enough. Sometimes we just can't get things back to work.

Repair is War on Entropy!

Update (03/13/25)

@fixer85785 remember it is possible that you have a component on the power rail that has shorted out. Most of those components get hot when you plug your motherboard in. That is where the Resin Vapor comes in handy. Or you can use some 90%+ isopropyl alcohol and wet the components with that. See if you find one that dries quicker then the others. That will be the one that is short. I'd start testing components in the areas of the larger coils. Those are usually power rail's of some sort :-) Biggest issue is that there are no schematics :-( What voltage do you get on the GATE of the IC's (Black to ground and Red probe to GATE pin for those IC's) when you plug your motherboard in?

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Thanks for all the in-depth info! I really appreciate it!

So are you saying that these MOSFETs are most likely failed, but that failure is due to another problem somewhere else?

Also, where would I check for a short to ground and for voltage on the gate? I know *how* to use the multimeter, but I don't really know how to apply that knowledge to testing the components on a motherboard.

Also added better pictures :)

Thanks again for all the help!

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@fixer85785 zoom in closer to the two MOSFETS. There will be a divet or a marked spot on a corner that denotes pin 1. On the SOP-8 N-channel Mosfet commonly pin 1, 2 and 3 are Source, pin 4 is Gate and 5 through 8 are Drain. Use your meter and place it in DIODE . Now place the probe on Source and one on Drain. You should get a reading. If there is no reading, or a continuity buzzer, you have a shorted MOSFET. There is a really good learning opportunity right here. Keep notes, do not rely on just a video that may disappear one of those days. Next place the red probe to ground of your motherboard, and the black probe to Source, you should not get a beep. Then do the same except black probe to drain, it should not beep. If it does beep you most likely have a short to ground, that means it is possible that one of the components in the power rail has shorted out. Since I do not have a thermal camera, I use a resin vaporizer to find the bad compopent. Check this video to see what I am talking about. At this point, I would really start off with the MOSFETS (get a couple to make sure you get some spares;-)

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I went ahead and tested the MOSFETs as you instructed, putting the meter in diode mode, and with the black probe on source, and the red one on drain, I did get a reading in diode mode. With the probes reversed, I got no reading.

When I put the meter into continuity mode, and put the red probe on ground and the black probe on source/drain, there was no continuity with either.

So that means either I tested wrong, or they're good? That might make sense, as from my limited understanding, which definitely could be mistaken, the MOSFETs have something to do with the power circuitry, and if they break, no power/incorrect voltages go to the machine. But the Ethernet lights do blink when the machine is plugged into power and Ethernet, so it seems as if power is getting somewhere?

So does all this mean the problem is some other component on the board?

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