Leeb Hardness Tester Faults: What You Can Fix and What Must Go Back

Jun 25, 2026 Hardness Testers 5 min read

Leeb tester faults follow a clear pattern. What you can solve yourself is in the screen, the printer and the cable; anything involving circuitry or the impact mechanism goes back to the factory.

1. Hardness reading off by about 50 HL

Three checks in order: measure the supply voltage; strip and clean the impact device of dust and debris; if both are fine and the offset remains, control-circuit components have drifted – return it.

2. Screen problems

Missing segments: open the housing and reseat the LCD driver IC a few times to clear oxidised pins. If segments are still missing, the display module is damaged and must be replaced.

Black or blank screen: confirm the supply voltage first. If power is normal, the circuit has failed – return it.

3. Printing problems

Overlapping print is nearly always jammed paper. Open the paper compartment and reload; no need to disassemble anything.

4. No reading on impact – the most common repair

Eight out of ten are the sensor cable. One end is a three-pin plug into the sensor, the other goes to the main unit; a fault at either end kills the reading.

The three-pin plug is moulded onto the cable, and the pin-to-wire joint is where quality shows. Cheap cables fail early. Always pull the plug, never the cable.

At the main-unit end the plug itself rarely fails; the usual problem is a poor solder joint, or the way it is pulled.

There is also a loose three-pin socket on the coil, or a broken solder joint between coil and socket. That needs internal inspection – return it.

5. Impact body will not be gripped or released

The three claws that hold the impact body are no longer on a common centre. Over time their spring tension changes, they loosen or shift, and the body slips on pickup or hangs on release – two claws holding, one free.

The tip of the impact body may also be worn. Both cases need factory adjustment or replacement.

6. Stiff loading

Dust has worked into the loading sleeve and onto the spring. Cleaning it yourself is risky – send it in.

Summary

Yours: power, screen contacts, paper, cable handling and cleaning. Anything involving the board, the sensor internals or the claws goes back – opening it only makes it worse.