Microrouter v3 with undocumented modifications.

[GillianS]

I'm trying to get a microrouter V3 up and running and having a spot of bother. The machine was built in May 2001 but has obviously been upgraded to the USB nextmove, and the "door drawings" have an updated set of 3A steppers, vacuum pump and Sprint 1200. How can I tell the difference between the Sprint 800 and the 1200 spindle board?

Things were going well to begin with and the nextmove connected and the motors pulled in once e-stop was reset. Things went South as soon as I clicked on "HOME", the z-motor squealed for a second or two and then silence, followed by that unmistakable smell of burning.

I've taken it apart and started probing. The z-axis L298 has a big hole in it, one of the catch diodes to ground was a dead short, the 6.3A PCB fuse was taken out and the L297 has a suspicious line running across it that looks like a package crack. I need to order some new parts and possibly replace the bridge rectifier while I'm at it. I'm sure that at least one of the other L298's has been replaced in the past too.

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I've had a look at the steppers and X and Y are the usual Sanyo Denki 2A types but the Z is a 3A/ph MAE HS200-2221 stepper (pictured). Can anyone confirm what stepper should be fitted to the z axis?
I'm wondering if the school that had this mixed up the controllers and this should have been a pro version or if the stepper failed, the wrong one was fitted. Having removed the faulty parts, I'm wondering if I should "side-step" the issue and use a DM542 or 556 and a fused 24V power supply and pick off GND,enable, step and dir from the nextmove for channel 2 and drive the stepper from that.

Any suggestions most welcome.
Gillian

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[GillianS]

As a follow up, The catch diode that went short circuit was one that protected from negative going back EMF by shunting it to ground. Yes, grounding an out out on the L298 would definitely let the smoke out. So would a zombie L297

I've checked out the stepper wiring in the cabinet and nothing seems open or short. The only thing that does look odd is the stepper wiring from the nextstep board is very thin compared to the equivalent wiring in my novamill. Tomorrow's task will be to check the microrouter cabinet wiring and z stepper for opens and shorts.

[kfm36]

Hi
I have a V4 Pro (Sept 2002) that was updated to the USB controller. All the axes motors are the 3A version from your photo and are powered from a separate Parker XL50 3-axis drive (5A capable) with the step/dir inputs taken from a header on the controller board. The controller stepper drives are not used and from the manual have a stated limit of only 2A per motor.

The spindle drive is from a KBLC-240 rather than a Sprint board.

Let me know if any photos of these would be helpful.

[GillianS]

Hi, thanks for the reply. Interesting. Mine is definitely the V3 with separate control cabinet shown below:

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I've pulled the wiring diagram from the door and compared and it's definitely a 13-2-2001 style of machine that seems to have been upgraded to a 9-11-2001 that includes "3A steppers", vacuum pump and sprint 1200. It's got the VPR relay but still retains the choke.
I've not got a separate stepper driver, and there isn't one in any of the diagrams - everything is driven from the denstep with the L298 2A steppers.... Perhaps 3A is calculated as 1.5A per phase, two phases = 3A?? Anyone form Denford able to comment? The L298 feedback resistors are still the 0.47R used on every other denstep I've seen.

One interesting observation is my board is using BYW98-100 which is a 100V rated part and other examples on the forum seem to be using the BYW98-200 which is a 200V capable part.
viewtopic.php?f=54&t=5728&p=23085&hilit ... tor#p23087

I'm wondering if the Back EMF from the MAE HS200-2221-0300 3A stepper is breaking down the 100V diodes. Perhaps that explains why the catch diode to ground on the A output went short. With the L297 coming out of reset at ABCD=0101, it would sit at hold fine but as soon as it was stepped, the upper transistor pulls high and current shunts straight to ground - Pop! I did check the diodes and drivers before I applied power and they were not shorted then

FYI, the inside of the little plastic BIM box with the router motor power socket and chocolate block connection to the stepper, switch (purple) and serial phase connection on the stepper. Is that Factory?

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I'm going to repair the board once a new L297 arrives and uprate the diodes and see what happens. If it goes pop again, I think a DM546 and external DC supply might win the day. Perhaps the next question is what's everyone's favourite stepper driver?

[GillianS]

My spare bits finally arrived so I spent an hour today soldering in the new L298 driver, a new diode, a fresh bridge rectifier and a socket to take the new L297 stepper sequencer. Ran a brush and IPA over the soldering to clean off the flux.

As I'd cleaned off all the old stuff, applied a thin film of new thermal compound all round to the heat tabs and ran some down the edge of the aluminium block. Was looking good so fitted the Denstep module back in the control box.

For testing, and because the magic smoke had been let out previously, I fitted a 2A fast fuse in case anything went wrong and checked the resistance on all the stepper wiring and verified nothing was shorted to ground or other signals. All the catch diodes showed the expected 0.4V drop in the forward direction. The rest of the testing was step by step for each axis using the magic of the "secret home" button to allow movement without homing first.

-pulled the stepper connectors and powered up the board. A current clamp round the AC feed showed near 0A. Powered down.
-connected one of the steppers for X, Y and then Z, checking the current each time while holding and when stepping. Knocking the E-stop is sufficient to kill power to the steppers allowing them to be plugged and unplugged safely. Each axis pulled 0.9-1.7A when idle to actively stepping.
*DO NOT (UN)PLUG A STEPPER WHEN POWERED* That would be enough to damage the drivers leading complete failure.

Having proved each axis with the 2A fuse, the machine was powered down and it was time and swap it out for the proper T6.3A and powered up again. In for a penny... with hand hovering over the e-stop while staring at the current clamp I homed all axes. Homed, no smoke or pop - Success

For a final test, I checked the vacuum pump, door lock and the spindle. Ran the spindle from min to max and checked the guard interlock prevented spindle start. I think it might be safe to say another Microrouter V3 is now back from the dead

Replaced L298, Catch diode, T6.3A fuse, L297 (in a socket), and thermal compound. The rectifier was replaced as a preventative measure. The observant may be able to tell which parts were changed.

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[GillianS]

FYI - If anyone has blown a stepper driver, it might be prudent to replace the companion L297 as well as it's often damaged as the L298 goes up in smoke. In my case, the control pins seemed high impedance compared with a working one and others were much lower.

Once it was removed, I put it under a microscope and noticed a small crack running round the device and a tiny blob of resin by one of the pins - definitely blown too.
As the '297 does all the clever chopping, any fault in the sequencer and current limit circuit will let the smoke out again.