Minisforum UM690 Main Board Removal

Last updated: Mar 27, 2024

This particular mini pc presents a puzzle when removing the main board. So, I am sharing my approach in hopes that it helps.

1 - Pry out the two rubbery feet and two triangular corner panels from the bottom; they are held in with some adhesive.

2 - Remove the four Philips-head screws just uncovered.

3 - Use a pick to gently pry off the bottom panel.

4 - Remove the four screws at the outside four corners of the main board. NOTE: DO NOT remove the four screws that are more toward the center of the board; two of which are underneath the memory cards. These hold in the processor heat sink and the metal thermal material to the other side of the board.

5 - Remove the SSD; don't lose the screw.

6 - Remove the Wi-Fi board that hides below the SSD; don't lose this screw either. The reason you are removing this is that the antenna lead is firmly attached to the case.

7 - The metal frame you can see around all four sides is firmly attached to the case. So, slip a pick between the metal frame and the front of the ethernet connector. Use this to gently pry the case side outward and the board upward. You may also need a second pick slid in between the metal frame and the far USB connector to keep it from catching on the metal frame. A little patience here and the board will be free of the case.

That's it. Mystery solved. Enjoy.

Software/Firmware Updates Ignorant/Annoying?

When a user installs a software update, why does the user have to answer any questions? The base/previous version is already installed and running. 

If the user has asked/agreed to an update and unless there are new options or other critical user interaction required, the software should just update itself silently.

Millions of person-hours are wasted with the user answering the same questions for every update -- over and over.

Samples of stupid questions:

Agreeing to the license (didn't the user already do that?)

Does the user really want the update - duh?

Click finish to complete the update (like there is another option).

NPN Transistor Saturation Mode Laboratory Measurement

The WWW has a lot of information, but finding actual circuit measurement of an NPN transistor saturation mode was, well, I never found any. Hence this experiment. I chose a common 2N2222A in a TO-92 package. On the DCA Pro 75, it measured:

hFE = 265 at Ic = 5.01mA

Vbe = 0.755V at Ib = 5.00mA

VceSat = 0.013V at Ic = 5.0mA and Ib = 1.00mA

 

The testing setup is in the following diagram:

 

A good description of a PN junction is give in this video: Forward biasing a PN junction.

A good description of an NPN transistor is given in this video: NPN Transistor Working.

Now for the actual measurements of our sample 2N2222A transistor: