How to use an oscilloscope to repair a switching power supply
Generally speaking, there are two grounds for parallel switching power supplies, namely "hot ground" and "cold ground". Taking the circuit shown in Figure 1 as an example, "◇" in the figure represents "hot ground", which is the ground on the primary side of the switching power supply and is connected to the mains ground. The base plate connected to the "hot ground" is called the "hot base plate"; The "up" in the figure represents "cold ground", which is the ground on the secondary side of the switching power supply and is connected to the load. The base plate connected to the "cold ground" is called the "cold base plate".
The fundamental difference between "hot ground" and "cold ground" lies in whether there is a "direct electrical connection" between the zero potential reference point of the machine base plate and the municipal power grid. The directly connected ground is the "hot ground", and the "hot ground" inside the aircraft has a voltage of about 100 volts to the ground. If the "hot ground" inside the aircraft and the components connected to the "hot ground" are accidentally touched, it is highly likely to suffer electric shock and even life-threatening; On the contrary, there is no direct electrical connection between the "cold ground" and the municipal power grid. Touching the "cold ground" and the components connected to it with your hand generally does not cause an electric shock.
For a series switching power supply, there is only one "hot ground", which means that the primary and secondary sides of the series switching power supply are the same ground, both of which are "hot ground". Due to the fact that the LCD monitor is directly connected to the computer host through cable signals, the switching power supply of the LCD monitor cannot be connected in series. Otherwise, it will make the computer host live, which is not allowed. Agitek Antai tests.
The oscilloscope is broken, there are some faults, and the screen is not lit. How to handle or repair it
If the screen of the oscilloscope does not light up, it is first suspected to be a power failure. If there is no light on the button board, it is likely a problem with the power board. If there is a light on, it may be a problem with a module on the motherboard, which needs to be disassembled for specific testing. The following points should be noted for issues caused by oscilloscope power failure:
There is an independent power module inside the oscilloscope that supplies power to the motherboard and various functional modules, so it is necessary to pay special attention to power safety.
Precautions during use:
1. Use the original power cord of the oscilloscope;
2. Confirm the stability of the power grid. When high-power electrical appliances are connected to the power grid, first turn off the oscilloscope, unplug the power cord, and wait for the power grid to stabilize before using it;
3. When starting up: First plug in the AC power cord, and then press the power button to start up;
When shutting down: first press the shutdown button to turn off the oscilloscope, and then unplug the AC power cord;
4. Pay attention to the operating environment of the instrument and regularly clean the dust.
