[warrenb]

Hello Y'all,

I have a centroid retrofit on my Bridgeport Boss circa 1993.

The control stopped recognizing the Y+ limit switch. I have pulled the board and the limit switch circuit works all the way up to the plug in to the control. I know the switch works and know the wires are good. I have physically tripped the limit switch in the parameters mode and the control does not recognize the switch in one direction. I swapped the switches and it is always the same input at the control.

I am not an electrical guy but traced the circuit board as far as a could to make sure continuity was good.

Any advice would be greatly appreciated. Thanks.

[Metzenw]

It sounds like that Input is burnt up. Nothing you can do short of sending it back to Centroid for a replacement.

Now, I have alittle experience with Centroid. But if the Y+ input is bad, change the homing file to home in the -Y direction and then set a software limit to your +Y Max travel, that will get you back up and running.

If not, the DC All-In-One board would be a good upgrade if its a very old system.

Also I sent you a PM about a guy you can call.

[warrenb]

Thanks Metzenw,

I have contacted your centroid guru. The price for repair is fair ($750). The upgrade is worth more than the machine (5500).

I have fiddled around with my multi meter and tested continuity, transistors, diodes, caps, and everything else I can think of from my remedial electronics knowledge. There are no obvious signs of burned out connectors so I am going with the assumption that it is the optoisolators on the board. How do I know??? I don't . but for $20 I ordered replacements for all on the board and will solder them in place of the originals.

I shall keep everyone informed of my progress. Sure...I may be pissing up rope, but if it turns out to be a $3 optoisolator then it is a good exercise. If not? Well, I guess I upgrade that hard way regardless. I'm only out $20 and my time. That sure beats thousands for an upgrade.

Wish me luck.

[cnctechml]

I have rarely seen a case where the components on the Centroid board were damaged other than if someone wired something incorrectly on a new installation or if there was a short somewhere in system.

I am going to assume that if you were quoted $5500 for an upgrade that you most likely have a Centroid M15 control, correct? With that being said, there are various different models of M15 controls. I am going to assume that you have a version in which the limit switch wires go to the Control Cable connector on the back of the M15, correct? From that control cable, the limits are plugged into a connector on the board that is mounted on the top sheet metal of the M15. Depending on the version of the M15 control that you have, that board will either be a SERVO1 or an M15DRV1.

If that board is an M15DRV1, you will be able to use the PLC Diagnostic menu to see the state of those inputs change. Depending on the software version that you are running, you may be able to press ALT+I from the main screen. You should see 3 or 4 rows of red and green circles. The top row are your inputs. There should be a description of what each input represents either in the center of the screen or to the left of the screen underneath the rows. Use the arrow keys to scroll to the right until you see the input for the Y+ Limit. If the input is red, the control believes that the limit is tripped and that it's not tripped if the input is green. If you do not see the PLC Diagnostic menu in the main screen, you should be able to press F7(Utility) from the main screen and then F6(PLC Diag). The inputs are located on the table on the left side. A value of 1 means that the limit is tripped while a value of 0 means that it's not tripped.

Now that you are on the PLC Diagnostic menu, install a jumper directly into the connector on the M15DRV1 drive between that input and COM. Remove the jumper. Verify that you see the input changing state. If you do, then the issue is not with the M15DRV1 and you do not need to replace any of the components. It could be an issue with the control cable that goes from the back of the M15 to the connector that plugs into the M15DRV1. If you never see it switch, then I would verify that the limit switch isn't defeated.

On the board that is mounted on the top sheet metal of the M15, whether it's an M15DRV1 or a SERVO1, there is a limit defeater switch. It should be a black component with white tabs. Unfortunately, I can't tell you exactly where it is as I do not know which board you have in your system. Each of the white tabs is for a particular limit, X+, X-, Y+, Y-, Z+, and Z-. Verify that the limit defeat switch for the Y+ Limit isn't in the up position which defeats that limit so the board never looks at the state of that input.

The use of the PLC Diagnostic menu mentioned above only works if the board that you have in your M15 is an M15DRV1 as it has the 3-axis drive and PLC built into that board. If your board is a SERVO1, you will not be able to check the state of the input in the PLC Diagnostic as the SERVO1 does not have a PLC section. All you can do if you have a SERVO1 is verify that the limit isn't defeated as well as install the jumper and verify that the control faults when you attempt to move in that direction. If the control does fault, then the SERVO1 circuitry is working as it should.

If after all of that has been checked and you are still not seeing the state of that input change, then I agree with you in that the issue is with the board. The cost for the repair seems a little high. The cost to repair something depends on what Centroid finds wrong with it but the minimum repair fee is $375. If you contact Centroid's Technical Support at 814-353-9290 x4 with your control serial number, they will provide you with an RMA number to send in the control to repair if that is the route that you wish to take.

[warrenb]

Thanks for the advice.

I am going off the top of my head here.... I do not know if I have the Servo1 board or not. That being said....

I ran the PLC diagnostics and that's where I see no signal reaches the limit switch. Jumping the connectors has no effect. All but that one input shows fine on the PLC.

I tested the physical operation of the limit switch all the way to the board and it is good. I have removed the board and tested continuity up to and through the small gang dip switch soldered in to the board. Continuity is good up to the optoisolator, which I have no way of testing. There is nothing replaceable on the board aside from some PICs (guessing on what brand) with stickers on them. And it is my experience with PICs that if it goes bad, it's all wiped out, so it wouldn't just be a single input. For the $5 each opto and 1 hour work I can replace the optoisolator between the dip switch and the rest of the control. If that's not it.... I might just build a new control. It's hard to justify the plug and play upgrade at $5500 for a $1000 machine.

[warrenb]

FYI. The board is the M15DRV1.

I will be replacing the chips this weekend.

[warrenb]

Hello Y'all. A friend loaned me his top notch multi meter that was way more sensitive than mine.

There is a bad diode which I will replace before I replace the optocouplers. If that's the problem then it's a simple fix that I can probably get a diode for free from some scrap circuit boards I have floating around. If not, maybe $2 at Radio Shack.

I'll keep everyone posted.

[Metzenw]

Well good luck, I'm not confident enough to replace surface mounted components.