Reico Sakura Multimeter

[pgr2002]

I have the Reico Sakura Multimeter. The front glass pane is broken. Of late this tester is not getting adjusted to zero ohms. The variable potentiometer of 1K was defective and hence replaced with new one. But still the working of needle movement towards zero is not full. It comes towards mid way and does not go towards zero ohms. Tried with new batteries but still the same problem. Could any one give their valuable suggestions to what happened and why this behaviour? I may require the circuit diagram of this tester. If any one has it please post it.

 

[betwixt]

If the glass is broken the fault is probably the zero screw above the range know has become disengaged from the needle pivot. A mechanical fault rather than electrical. If you can access the back of the adjustment screw you should find it has an offset pin behind it that rides up and down a slot as it turns. As it does so, the slot moves from side to side and 'zeroes' the needle. You will probably find the pin is no longer inside the slot and is pushing on one side of it instead.

Brian.

 

[pgr2002]

If the glass is broken the fault is probably the zero screw above the range know has become disengaged from the needle pivot. A mechanical fault rather than electrical. If you can access the back of the adjustment screw you should find it has an offset pin behind it that rides up and down a slot as it turns. As it does so, the slot moves from side to side and 'zeroes' the needle. You will probably find the pin is no longer inside the slot and is pushing on one side of it instead.

Brian.

Thank you for the reply.
The screw is not loose or disengaged. But it is sufficiently tight enough to enable the needle movement. I tried and turned the screw but was not useful since the needle stops mid way while testing. This meter uses only 2x1.50v cells and there is no 9v battery inside as some of them have. Can there be any change of my connecting the wires wrongly/differently when I changed the potentiometer of 1K. I will have to check but without any hints of a diagram it will be only like groping in the dark.

 

[BradtheRad]

The zero ohm knob is where the potentiometer is. It's different from the zero screw adjust.

You short the leads together (creating zero ohms). Then turn the knob until the needle reads zero ohms (full scale). Did you at any time see it behave this way normally?

Are you certain you wired the new pot correctly?

My meter leads develop bad connections every once in a while due to flexing. Therefore as a test when zeroing the ohm reading, try touching a short length of wire across the jacks, to connect with the least possible resistance.

Healthy meter leads have about 0.4 ohm resistance. That's what I see with my digital meters. However an analog meter permits you to zero out that small amount.