Triac Problems - Stepper Driver Dead

[davidimurray]

Well having gone to all the trouble of retrofitting the old stepper and spindle drivers into a new cabinet and getting everything working with Mach 3 - my Z axis groaned, vibrated and then ground to a halt. The machine has been working brilliant until now.

Now I've tried swapping the Z and Y axis stepper driver boards over and the fault moves with the board - so the finger is strongly pointed at the SD3 card. I've checked the fuses on the board and they are fine. I alos tried swapping the L297 chip between two boards and regardless of the board the fault stays with the SD3. Now the interesting bit. The first time the fault happened, the stepper driver was locked solid when powered up. I hit home, drive started to move then started stalling and then stopped. Grabbing hold of the stepper motor shaft there was still some holding torque there, but nowhere near as much before. Once the drive had been turned off all the holding torque had gone and I could turn the motor easily. Having not been in the workshop for the week I plugged the SD3 back, turned it on and by magic the motor had full holding torque. However within about 30 seconds I tried to jog the axis, there was some clicking and grunting and the motor failed to move followed again by reduced holding torque. Looking at the SD3 board the only thing I can see that looks untoward is of the 3 big capacitors on board- the smaller of the 3 has some cracking of the end cap where the lead comes out. Do you think this could be the cause and does anyone have any experience of fault finding the SD drivers? Cheers Dave

[angel-tech]

Hi Dave, it maybe one of the drive chips on the heatsink if not the pair. L298. I'm placing an order to Rapid today ish, if you need any.

Tom.

[angel-tech]

Dave, would you like to borrow a drive until you get yours repaired

[davidimurray]

Hi Tom

Sorry for the delay in getting back to you. Hopefully I'm now sorted - got hold of a secondhand unit. Just need to swap the heatsinks and we should be back in business

One interesting thing I noticed. If you look at the SD2/3/5 Manual at the jumper settings it says LK1 - leave fitted, LK2 do not fit. The new drive I have is setup this way, but if you look at the original drves in the Triac they all have Lk1 not fitted and LK2 fitted - i.e. opposite to the manual. Anyone know what that is all about?

[angel-tech]

I have one of the early triacs like yours here, and the x drive has link 1 fitted, but the y and z has the link on link2.

[davidimurray]

Had a closer look at my mill today and the jumpers are setup the same as yours. I tried installing the new drive with LK1 fitted and the motor just hummed. Switcjed it with LK2 (like the Y axis setup) and it now works perfectly.