Graphics card mining topic - Graphics card maintenance tutorial series 1: Common tools and instruments for maintenance

Three years ago, I was fortunate enough to be invited by the editor of Caiyunbit to write a technical article on power supply, but I never had the time to write it. In early 2021, I brought up the old story again.

I thought that the maintenance of various power supplies and mining machines in the mining circle is very mature. However, high-end graphics card maintenance technology is extremely rare on the Internet. After half a year, the number of mining graphics card maintenance has increased sharply, so I made a graphics card maintenance tutorial to increase website traffic and return the favor of my friend for giving me a platform to play my role.

The tutorial uses the rx570 drawing as an example (I only have this drawing), so I use it as an example to explain the graphics card repair technology (regardless of the circuit architecture of A card or N card, there is no difference, and it can be applied by analogy). Due to the uncertainty of the user group of Caiyunbit's traffic and whether I have enough time, I don't know whether the focus is on beginners or experienced engineers. I hope to adjust the subsequent content of the tutorial through the traffic feedback of the website.

This tutorial is written by Chengdu Benwo Electronics Co., Ltd. The purpose of knowledge is not to show off and discriminate against others, let alone become a tool for exploiting others. The real value of knowledge lies in sharing. This tutorial has no copyright and can be circulated, shared, published, etc. If you can kindly indicate the source, I will be grateful and grateful. This tutorial is written in the most rigorous, comprehensive and meticulous principles, but mistakes are inevitable. Because I am a big-headed person, I hope that the readers will not be tolerant and point out the mistakes in a simple and rude way.

I would like to give special thanks to my friend Caiyun Yangguang for providing the platform, and Teacher Tang for giving me advice on graphics cards.

Chengdu Benwo Electronic Technology Co., Ltd.

WeChat: weixiu3721

Email: [email protected]

January 17, 2021

The tutorial is divided into several parts:

1. Preparation and use of common tools and instruments for graphics card maintenance

2. Graphics card component identification and working principle

3. Graphics card architecture and runtime

4. Power circuit failure and maintenance

5. Bios circuit failure and repair

6. Video memory and GPU circuit testing and maintenance

VII. Comprehensive testing and maintenance examples

1. Use of tools and instruments

1. Soldering Iron

It is recommended to use a high-frequency soldering iron with a t12 heating core, because it uses a high-frequency coil for heating, and the heating part and the temperature sensor are very close to the working part, so it has the characteristics of fast heating, fast temperature recovery, and fine temperature control. The following are solutions to problems that novices may encounter when using a soldering iron:

1) Use a knife tip as much as possible for the soldering iron tip

The reason is that the contact area of ​​the blade is large: due to the tension between molecules, the soldering iron tip and the circuit board pad determine who has a larger contact area with the tin and who is more likely to absorb the excess tin.

2) The soldering iron must be used with flux

◆ The function of flux is to clean the organic oxide layer and increase the fluidity of tin. If there is no flux (the solder wire structure is hollow to allow for the injection of flux), the solder will be as sticky as glue and cannot flow into the uneven solder joints, resulting in empty solder joints. There is also a thin film blocking the contact point, which prevents the solder joint from being fully in contact, resulting in poor contact and the soldering iron tip cannot absorb the tin.

◆ The criterion for judging the absence of flux is that there is no smoke or the tin becomes very viscous during welding. In this case, please stop welding, add more flux (tin wire), and then weld again.

◆ For pads with very small contact points such as flying leads, please adjust the temperature to around 220 degrees, the melting point of tin (slightly different depending on the lead content), to ensure that when soldering is stopped, there is no excess heat that affects the solidification of the solder and causes the shaking handle wire to separate from the pad again.

◆ Cotton wool has more fiber layers and more wrinkles, so cotton wool plus water is better for cleaning soldering iron tips than the standard sponge.

◆ When the soldering iron tip becomes black, oxidized, or stained with debris, please adjust the temperature to 220 degrees (too high will regenerate the solder mask, too low will make the solder mask too hard to erase). Put the soldering iron in the cleaning seat for cleaning and quickly coat it with a layer of tin for protection.

2. Preheat the soldering station

Figure 1

Figure 2

Graphics cards are high-speed circuit boards, and the GPU core power supply current reaches more than 100A. Therefore, thick copper foil is used as the power layer and ground layer when designing multi-layer PCB wiring to shield high-speed signals and increase the heat dissipation coefficient. Therefore, the thermal conductivity is very strong during welding, resulting in serious heat loss when welding most components. Whether it is a soldering iron or an air gun, the heating temperature cannot keep up with the heat dissipation temperature. Therefore, use the infrared preheating soldering station in Figure 1 to preheat the graphics card to the lowest melting point of the solder limit: 180 degrees for lead soldering and 225 degrees for lead-free soldering.

When soldering balls on GPU, some steel meshes are too thin or too soft to be directly heated and deformed, messing up the solder balls. Or the wind from the air gun blows the solder balls away. So use the soldering station in Figure 2 to solder the GPU with solder balls installed. Add a silver cover that can reflect infrared heat to prevent air flow. Under the condition of heating slope of 3 and using lead-free solder balls, the soldering can be completed when the temperature of the constant temperature soldering station reaches 235 degrees.

Note: When the temperature reaches 235 degrees, remove it immediately to prevent the GPU from being damaged by overheating.

3. Heat gun

Figure 3

Figure 4

When disassembling SMD components during graphics card repair, a hot air gun is used. The difference between Figure 1 and Figure 2 is that the air gun has different air blowing devices, resulting in different characteristics.

The blowing device in Figure 1 is on the handle, and the flow pressure of the gas is constantly changing according to the rotation of the fan, so the hot air flow is constantly changing, and the temperature of the heated part is relatively uniform. However, the wind speed of the fan is low, so it takes a long time for the heat to reach the destination, and the heat loss is serious, resulting in low heating efficiency.

The air pump hot air gun in Figure 2 has high heating efficiency due to high air pressure, but it forms different pressures in the air outlet, and the heat output is not uniform. When the heated part is hot and cold, the thermal stress and expansion coefficient of the components are different, and the resulting destructive deformation usually causes the chip's internal pins and the silicon-aluminum bond to break, causing damage to the chip.

Therefore, in graphics card repair, novices use the air gun in Figure 1 for safety, while experienced engineers use the air gun in Figure 2 for efficiency.

Problems encountered when using air guns:

1. Use of flux: Adding flux to some aged and severely oxidized components can make the non-heat-conducting oxide pins loose and easier to conduct heat, thereby reducing physical stress and making it easier to disassemble. At the same time, the size of the smoke generated by the vaporization of the flux can be used to determine whether the temperature of the heated component meets the requirements. Due to the principle of physical vaporization heat absorption, if the flux is not dry, the temperature of the heated device will never reach the boiling point of the flux under normal pressure. This achieves the purpose of protecting components and PCBs from damage.

2. When heating and removing the components, although the heating temperature does not reach the PCB damage limit temperature between 240 and 280 degrees, the influence of the PCB via copper injection process, if the hot and cold are too uneven, it may also cause the via to be blocked, and in severe cases, it may also cause a broken wire. To prevent this from happening. As shown in the figure below, take the high-air gun muzzle (different temperatures and wind speeds lead to different heights. Quick 861, 120 wind speed, 500 degrees temperature) about 5cm away from the PCB to quickly shake and heat the area inside the circle, and then heat the slow components in the box. Personal habit is usually to heat the circle for 1 second and the box for 4 seconds (not the best operating method obtained through scientific experiments). It can prevent the expansion coefficient from being different due to uneven hot and cold, so that the vias of the PCB that does not meet the copper injection process or is severely aged will not be blocked or even broken.

3. When the temperature reaches the disassembly requirement, to prevent small components from being blown away, please apply flux on the small surface of the small components and fix the circuit board on a stable support point to prevent shaking and falling of small components.