1. First look at the screw fixing port. Those who have used the machine usually have ring-like traces of screws. Some have added insulating gaskets (some chassis come with gaskets), but not There are ring-shaped traces of twisting and rubbing, but if you look carefully, you will find some marks - the outer ring is not covered by the gasket, and the oxidation color is different from the inside!

In addition, look at the fixing hole on the back of the board , the screws must have been screwed on - there are more or less traces of being pushed by the nut posts on the back panel of the chassis! Look carefully.

2. Some boards are not strictly second-hand. For example, many of them are now This is a popular practice among merchants—putting up a prototype without a chassis and running it for display. After a while, the board will be put into a packaging box and sold. But in the memory buckle and the graphics card slot buckle, There will be unclean marks and slight scratches on the edges of the CPU card holder and other places! Usually when I encounter this, I will insist on asking the merchant to replace it.

3. The above method also works. Suitable for other boards for auxiliary testing. For some second-hand or refurbished boards, the workshop will melt the solder on the screw port and make it look like new, but the buckles, etc., and the I/O baffle equipment behind the motherboard (such as PS2 port, USB port, etc.), there will be scratches or traces of plugging and unplugging.

Some workshops will suck out the solder from the screw port, leaving a circle of copper layer. This kind of look It seems to be new, but be careful, because the new boards coming out of the factory are all welded.

4. Second-hand or refurbished boards have dirt in some small parts, such as the I/O baffle. Under the mouth of the equipment. Of course, some workshops will use microwaves (I remember this method) to clean. Others use alcohol or an industrial detergent (I forgot the name, after all, I came into contact with this industry a long time ago). Anyway, after using the detergent, the board looks new (including the oxidized and stained solder, which is also new), but it has an acidic smell. And the new board has a spicy electronic component smell.

5. Many of the second-hand or refurbished ones have traces of repairs. The most common one is line repair welding. On the neat circuit lines (generally called "snake lines"), there is a small section that is artificially welded.

A skilled master can even weld a copper wire directly!

You can also check the solder joints of components. After all, manual welding and factory machine welding have different regularity.

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As I said, the three items 2, 4, and 5 belong to "experience". Especially 5.

Experienced people who often come into contact with this type of board seem to be able to "smell" it. You can often go to the second-hand market and look at boards, such as Shipai in Guangzhou. Over time, you will feel better.

Additional note: In fact, it is very interesting to buy this kind of boards. I once bought them at a price of 160 yuan. I bought a refurbished second-hand Asus nForce2 in 2004. The north bridge supports 400 FSB and a SATA interface.

Everywhere is new, except for one snake-shaped cable and a little welding mark. I guess it was a new board that was hit and disconnected, so I bought it. I’m still using it now, it’s pretty fast, haha.

Go to the second-hand market often. It’s fun