Hi everyone, I'm trying to repair an old Mac Mini from 2012. From a purely economic standpoint, it's obviously not worth it, but I'm more interested in the learning experience. The board is an 820-2366-C, and I haven't been able to find any schematics or .brd-files for it. When I connect it to the power supply, the fan runs at maximum speed, but nothing else happens. No beep, no LEDs. The power supply voltage is stable at the input connector. I'm measuring several shorts at SMD capacitors, but I can't pinpoint where the short is. A borrowed thermal imaging camera shows no abnormalities. What's the best way to proceed?
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I still have mine also. It has been running Catalina v10.15.x lately
It's the Intel-i5 model. A few years ago, I finally upgraded the ram to 8gb (still in dual channel)
I upgraded it's main-drive to a SATA-3/600 SSD within a few months of owning it back then. The old 500gb spinning-HDD went into a small USB-3.0 external-enclosure for Time Machine backups.
Surprisingly, Apple included Mac-Mini_6,1 in their CA-2023 updates. -
The fan spinning at maximum speed simply means the motherboard isn't functioning properly—the most basic operating conditions for the circuits haven't been met. This is the fundamental operating principle and power sequence for all computers. You should try the following steps:
1. Check the isolation/protection circuit: You said the input voltage is stable, but is it passing through the isolation MOSFETs? Find the main current sensing resistor and measure the voltage there. If PPBUS_G3H is not present or too low, your DC-in MOSFETs are not opening.
2. Check the SMC power supply: This is the "Always On" 3.42V rail. If this is missing or shorted, the SMC won't initialize properly. Measure the inductor for this specific circuit.
3. Check the 3V/5V standby voltages: Measure the resistance to ground and the voltage on the large inductors (coils) for the 3.3V and 5V rails. A short on the 3.3V line is extremely common and will prevent the board from waking up.
If all these checks come back normal, then the CPU side might be dead. However, the vast majority of issues lie in the preceding power supply stages. You need to measure their resistance to ground to rule them out step by step.
As for using a thermal imaging camera... well... that's mostly for finding direct shorts. In my experience, very few people use thermal cameras for computer motherboard repair unless it's a tiny, hard-to-detect short. It's used a lot more in mobile phone repair nowadays.
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Vizio e601i-A3 - Has Sound and Display, But No Backlight - Bad Power Supply Board or Bad LED Bulbs ?I was given this TV from my great uncle. He said it just wouldn't turn on one day out of nowhere, replaced the TV, and gave it to me to possibly fix and use for myself.
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