Series I, step motor help. Again.

[RickRe]

Okay. Finally got z axis to move on the mill. (After changing all the transistors out I found it was just no. 9 wire came off the k8 connector.) However, now the motor will start to turn, stop, and then just spin (run) without turning the belt. Any ideas where to go now? Thanks in advance. Rick

[kewl_cat]

Still sounds like one of the transistors is bad or a cold soldered joint. I know from experience

[RickRe]

Thank you. Just went out and checked and yes I found a shorted transistor. Changed it out and still the same thing. It wants to go but just sounds like its spinning. I can get it to step but do not trust that it is stepping in the right increments. I'll go back out and check my soldering job. Hope that is it. I'm about to pull my hair out. What about the little diodes(?) that go between the transistor posts? Can those go bad? Also is there a good reliable way to check the transistors without un-soldering them? Thanks again for any help I can get.

[kewl_cat]

Yes, I have had those diodes go bad. I used to check the diodes every time I replaced the transistors. I don't remember if you can check the diodes in place or not.

Keep us posted.

[RickRe]

Would a bad diode cause this also? X and Y axes work normal. Checked the soldering. Seems good. Guess I'll start pulling the transitors again and checking them outside the plate. Wish they would have put them in differantly. Like a plug in set up. If anyone has any sage advice I would be most happy to hear it.

[kewl_cat]

You don't have to pull the transistors to check them. I used my Flukemeter to check the transistors in place(diode function I think). Check it across the terminals and read the number and then reverse your probes and observe the new number. There will be one transistor that reads differently than the others. If both ways reads basicly the same then that is the bad one.