[tsquint1138]

I'm retrofitting a BOSS 4 with the original drives & steppers. All axis (XYZ) were working yesterday. Fuse 6 blew (I think it was 6. It's the 1.4A on the Limit overide circuit.) Replaced it today, now no X Axis

I can jog Y & Z but not getting any movement on X. I can hear the X axis stepper hum when it gets the signals from mach3, and the mechanical counter twitches.

Here's what I've Tried in troubleshooting problem.

Checked current across fuse12 & set ACC P1 to 8.2amps static.
Swaped SMD board with Y. Y works with X axis SMD board, X does not move with Y board.
Swaped pins 1&2 with 3&4 on K8 connector. Y Axis moves when 3&4 are connected to pins 1&2.
Checked continuity from K8 pins 1&2 with the card edge connector on X axis SMD socket.

SMD Board swap should have ruled out bad SMD Boards. K8 Pin swap should have ruled out bad BOB.



Any help would be much appreciated.

[Superman]

I'm going to throw a wobbily at you.

Are you sure it is electrical ?
Can you move the axis leadscrew by hand with power OFF ?

Might be a bearing or a motor lockup ( mechanical fault )

[machintek]

Check final drive transistors for a short.
2N6547.

George

[tsquint1138]

You mean Q1-Q4 on the SMD? (Those have been replaced in the past and are no longer that number -Have not looked them up to see if equiv.), Don't see 2n6547's anywhere.

I swaped X & Y motor wires at terminal block. Y drive runs X Motor, X drive fails on Y motor. Can swap SMD boards with no change.

[tsquint1138]

Checked the final drive transistors (On the big heatsink in mounts for each axis behind the ACC & SMD boards Right?) No shorts, Swaped the X & Y Transistors, (moved each assemby & re-wired) No change. X still fails.

[tsquint1138]

Fixed it!!

The diode across motor winding X2 to power resistor 87 failed to a short.

Replaced it with the biggest rectifier I could find in my parts bin to test, and axis works fine.

Now to order the proper part.