Troubleshooting tips for common keyboard failures

Computer keyboard in the course of use, the failure of the form of expression is a variety of reasons are manifold. There is a bad contact fault, there is a mechanical failure of the button itself, as well as logic circuit failure, virtual welding, false welding, desoldering and metal hole oxidation and other failures. Maintenance should be based on the different fault phenomena analysis and judgment, to find out the cause of the failure, the corresponding repair. This article is mainly for the keyboard common fault maintenance skills Daquan for everyone to explain, I hope you like!

Computer Trouble repair Daquan: the maintenance skill of common malfunction of keyboard

Common failure: Some keys on the keyboard, such as the space bar, enter does not work, sometimes, you need to press countless times to enter-or two characters, and some keys, such as the cursor keys are no longer up, the screen on the continuous movement of the cursor, the keyboard other characters can not be entered, you need to press again to bounce up.

This fault for the keyboard "card key" failure, not only the use of the old keyboard for a long time, there are individual unused for how long the new keyboard, keyboard card key failure also sometimes occurs.

The keys phenomenon of keyboard appears mainly caused by the following two reasons:

One reason is that the position of the plunger under the key cap offset, so that the key cap pressed and the key body shell can not bounce and caused the card key, this cause more than the new keyboard or the use of the keyboard soon. Another reason is that after long-term use of the button, the reset spring elasticity becomes very poor, shrapnel and the friction of the bar to become larger, can not make the keys bounce and cause card keys, this kind of reason is more in the long-used keyboard.

When the keyboard has a card key failure, you can dial the key cap and press the lever. If the rod does not bounce or fatigue, it is caused by the second reason, otherwise for the first reason.

If the key cap and the key body housing the cause of the "card key" failure, you can put a gasket between the key cap and the key body, the gasket may be made of a slightly harder plastic (such as an abandoned floppy disk jacket), the size is equal to or slightly larger than the size of the key body, and in the position of the bar through the opening of After it is set on the stick, insert the key cap, and use this gasket to prevent the key cap and the key body stuck, you can repair the failure button;

If due to spring fatigue, the cause of the tension of the shrapnel caused by the card key failure, then the special key body open, slightly stretching the return spring to restore elasticity; Remove the shrapnel to restore the key body. By removing the shrapnel, the resistance is reduced by the lever and the fault button is restored.

Common fault Two: Some characters cannot be entered.

If only one key character cannot be entered, it may be that the key fails or the solder joint is not welded. When checking, open the key according to the method described above

Measuring the on-off state of the contact with a multimeter resistor. If the key is pressed at all times, it indicates that the key reed fatigue or poor contact, need to repair or replace, if the key press the contact is broken normal, the explanation may be due to virtual welding, desoldering or gold chip hole oxidation, can be measured along the printed line step by step, to find fault for re-welding; if the oxidation of metal pores, the oxide layer can be washed clean, And then re-weld firmly, if the metal hole is completely off and cause the circuit breaker, can be additional solder lead to connect.

Common faults Three: if there are multiple keys that are not in the same column and are not in the same row, they cannot be entered.

It could be a line or line line somewhere, or it could be a faulty logic gate circuit. At this time, the 100MHz high-frequency oscilloscope can be used to detect the faulty device, and then repair the spot.

Common trouble Four: keyboard input is inconsistent with the characters displayed on the screen.

This type of failure may be caused by a short circuit on the board, which is displayed as the same column of other characters by this key, when the multimeter or oscilloscope can be measured to determine the point of failure to repair.

Common failure Five: press a key to produce a string of multiple characters, or the key when the character jumps.

This behavior is caused by a faulty logic circuit. First select a column of characters, if the row does not include a column of the return, there may be more than one character phenomenon, if a column with a return key, will be generated character jumps and can not enter the system last phenomenon, with the oscilloscope to check the logic circuit chip, find fault chip replacement of the same model of new chip, troubleshooting.