What is the reason why the monitor has no image?

ByAnderson Spaventa 2020-01-20 1019

Everything is fine when the monitor is turned on, but after a while there is no raster, no image, and a slight squeak. From the point of view of the fault phenomenon, it is the unstable fault of the display. Using the cooling method and heating method to check the main circuits of the display, no problems were found, so the following checks were carried out:

(1) check whether the output voltage of the power supply (90V) is normal, and the measured result is OV, which indicates that there may be a fault in the power supply or a short circuit in the main load. The existence of either of the two problems will cause the output voltage of the switching power supply to be OV, that is, the power supply has no output voltage. However, because there is a squeak, indicating that the power supply has oscillated but the frequency is abnormal, it can be considered that the power supply is basically normal, and the load circuit should be checked emphatically.

(2) cut off the connection between the line output transformer and the power supply voltage, and the measured power supply output voltage is 90V normal, indicating that the fault is really in the load circuit, and the line output circuit is the main load, so the output circuit is likely to be short-circuited.

(3) check the line output tube, line output transformer and other components, all in good condition, no breakdown short circuit phenomenon, why as long as connected to the uplink load fault occurs, while the inspection line load circuit did not find the broken components.

It is estimated that there are two reasons: one is that under the condition of high voltage pulse, a certain insulation material of the line output tube and line transformer is broken down to form a short circuit, and the other is that the insulation resistance of the 90V power supply to a certain part of the line output circuit decreases, resulting in a similar short circuit phenomenon. the above two points cannot be detected with a multimeter.

(4) by using the method of replacement, the mica sheet between the collector of the row output tube and the heat sink is replaced with a new one. Boot test, troubleshooting.

 You may also want to read:
 Xiaomi Mi Watch Color VS HUAWEI Watch GT2 VS Amazfit GTR: Which is More Worth Buying?
 Xiaomi Mi Watch Color In-depth Review: Fashion Products Without Electricity Anxiety
 How to Turn your Xiaomi Mi Band 4 as a remote shutter for Android camera?
 How to hide the display notch of Redmi Note 8 and Redmi Note 8 Pro?

Gearbest Daily deals up to 69 percent off

Extensive Product Selection

● Over 300,000 products

● 20 different categories

● 15 local warehosues

● Multiple top brands

Convenient Payment

● Global payment options: Visa, MasterCard, American Express

● PayPal, Western Union and bank transfer are accepted

● Boleto Bancario via Ebanx (for Brazil)

Prompt Shipping

● Unregistered air mail

● Registered air mail

● Priority line

● Expedited shipping

Dedicated After-sales Service

● 45 day money back guarantee

● 365 day free repair warranty

● 7 day Dead on Arrival guarantee (DOA)

You might also like


Related Products