The reason why the multimeter does not display and the short-circuit switch displays
1. Release the test lead and observe whether the pointer can return to zero at the starting position on the left. If it cannot be reset to zero, insert your fingernail into the bakelite adjustment eccentric rod at the base of the adjustment pointer to reset it to zero. There is no response from the adjustment, and the small internal rod is broken. If it can be reset to zero, place the meter on both sides of the table and hold it close to the table and shake it left and right, and observe whether there is any obstruction halfway from the leftmost to the rightmost point of the meter. Any obstruction indicates that the pointer scratches the dial or the glass. Take apart and repair. No problem, go to the next step.
2. Adjust the zeroing knob all the way to the right, which is the maximum zeroing correction amount. If the red test lead touches the metal seat of the black test lead socket, and the black test lead touches the metal seat of the red test lead, it is equivalent to two test leads connected in parallel. If it can return to zero, it means that the test leads have poor contact, check and rule it out. Cannot reset to zero, go to next step
3. Open the bottom battery box cover, take out the 1.5 volt battery, and set the multimeter to the DC voltage 2.5 volt range. Check whether the battery has 1.5 volts. If it is not enough, replace it. If the voltage is sufficient, observe whether there is oxidation and rust on the positive and negative electrode shrapnel of the battery box. If so, remove it. No rust, adjust the shrapnel to enhance contact with the battery, and install the battery. See if it can be reset to zero. Cannot be reset to zero, next step.
4. Open the meter box and observe whether the zero return wire is wound around the center contact of the potentiometer to see if there is any poor contact or the resistance wire of the potentiometer is broken. No problem, next step
5. Check the contact condition of the ohmic position of the shift switch and observe whether there is poor contact in the switch. No problem, go to the next step.
6. Observe the small wire-wound resistor with ohm x1 level to see if it is burnt.
If the first five steps are normal, the problem lies in the sixth step. Usually someone does not pay attention and mistakenly turns the ohm setting to measure the voltage, which burns out the small internal wire-wound resistor, causing it to fail to return to zero. Accurately match the resistors with the same resistance and the fault will be eliminated.
