i have a problem with spindle speed not being shown in S true speed readout box , on start up of the spindle using the M3 command in a program the spindle starts up and the true speed readout shows the spindle speed but then goes straight down to zero , because of this happening the lathe will not thread . i have been trying to solve this for weeks even buying another spindle index board but this has made no difference . can anybody please help me solve this problem . this machine has run perfectly over the last 2 years with no problems
MACHINE
Denford Orac cnc Lathe
mach 3 turn version 062 with the standard lathe screen
using parallel port
stepper motors 10x microstepping with 4.2A stepper motor driver
C3 index pulse board - settings - output TTL & active low
slotted disc on spindle has 1 slot x 12mm wide

You have Input 1 and Index both assigned to the same port and pin number, maybe there is a conflict there?
Hood

I also see you have the Spindle Relays disabled. Unless you are using a very old version of Mach then I am almost  certain you need the relays enabled when using the PP.
You do not actually have to have them connected to any relays, you can just set them up as ghost outputs, you will need to make sure however you assign to unused Outputs.

Hood

hi
thank you for your quick replies , something i forgot to put in my original posting is that the speed is manually operated with a switch for on/off and a pot for the speed control
i will try all your suggestions tomorrow thank you
robert