I have a TX350 sportcraft treadmill, works great, but shocks our hands everytime we use it and we lost the user manual when we moved a few years ago. ?

Burned out PCB?

When I lost the key for my treadmill I used a magnet instead and it worked fine.

http://rarajaxm.blog.com/2014/02/11/sportcraft-tx-5-0-rc-treadmill-user-manual/

I am not sure they carry these boards but most certainly worth a call is Allied Electronics. If they don't have one I know they will steer you the right direction.

Have you checked the outlet?

It is a simple magnet and Hall effect transistor if you have 2 small wires. It usually attaches to the 1/8 inch mini plug. You can test it with an analog meter, the resistance will be stable at rest, and with treadmill in motion, the resistance will change as the magnet passes the hall effect switch. moving the track at slow speed manually will be enough to see the needle move. Speed is calculated off of the rate of those pulses.

Watch this videos+ tips carefully:
http://www.youtube.com/watch?v=qgb2TY3WCkg&feature=related
http://www.youtube.com/watch?v=-oeXTKqWECw&feature=related
http://www.youtube.com/watch?v=GPI6dFJCUA4
http://www.youtube.com/watch?v=bF3OyQ3HwfU&feature=related
http://www.fixya.com/support/r10724803-measure_voltage_in_transforme_fitness
http://www.fixya.com/support/r10786838-test_procedure_dc_motor

http://www.youtube.com/watch?v=23ZgWaVEQjA

Please tight every conection, wire, loose conection, corroded cables.

https://www.mainetreadmillrepair.com/sportcraft-tx350-treadmill

I have a TX350 sportcraft treadmill and I keep getting shocked when I use it. How can I stop it ? I no longer have the user manual for it either. Can I get one ?

Follow the steps from the user/assembly manual in reverse. Find the manual here:
http://us.home.lifefitness.com/resources/content/8/2/0/documents/T3%20Manual.pdf

Installation begins around page 9