Full-Step config not working?

I have recently changed my Z axis a #10-24 lead screw. This is a 24 Turns Per Inch screw which is 1.058mm [(1/24)*25.4] and have calculated my steps per mm for the Z axis and ended up with 188.98 with full steps [(200 steps per rev * 1 step) / 1.058mm]. This gives me a resolution of .005mm per step. So I powered down the RAMPS board, removed it from the USB connection and removed the Z axis driver (A4988). I then removed the 3 jumpers and replaced the driver. I reconnected to the RAMPS board and changed the steps per mm to the above value using the G-code command M92 Z189.98. I then store the setting to EEPROM with M500. When I issue the G-code G92 Z0; followed by G0 Z50; then Z axis only moves upward by 3mm. Anyone ever encounter this?

I would guess you have a ultra cheap and nasty ramps that has pcb tracks under the micro stepping jumpers.

So regardless of if you have jumpers on or off they are always on

Test with a multimeter, there should be no connectivity between the pins with the jumpers off

Thank you!

Yes it is a nasty cheap board. And yes every stepping jumper is shorted under every driver chip. What a lovely feature! Seeing how the RAMPS board doesn't like me setting my z axis at 3000+ steps per mm, it looks like I need to pull the headers and cut the shorts out. At least now I know I'm not an idiot, just a little hard-headed about the cheap hardware.

There is another trick which I have seen but not tried if you wish to try it.

Take a read of this. [forums.reprap.org]

ie use a lipo battery (high current source) across the pins (without jumpers obviously) Use thick wires...
The tracks underneath don’t stand a chance.