I have a PCNC 770 mill. It is suddenly unable to boot, and I have not been able to identify the problem.

When I first turned it on today, it froze with an on-screen message instructing me, as I recall, to contact my administrator. When I rebooted, it omitted that message but got only as far as showing one of the splash screens, then froze. A power cycle gets me to a text menu offering the options of re-attempting PP (no luck), a Tormach-only option, and an option to reload an older version of the software.

I concluded (probably erroneously) that the software must have been corrupted. I have copies of everything, so when I was offered the option to scrub the HDD and restart from some earlier version of PathPilot, I took that. The system rebooted normally under PP 2.0 (I think), and I started the process of upgrading to 2.7.1. After the obligatory power cycle, it got part way into the PP boot, then froze while showing one of the splash screens. The Controller LED on the panel never illuminated.

I have tried to follow the troubleshooting instructions in the manual. The troubleshooting procedures of Table 2.1 refer to a button on Contactor C1, but Figure 10.9 identifies the left-hand, larger contactor as C2. The smaller, right-hand contactor has no button. I here follow the nomenclature of Figure 10.9.

When first powered on, there is a single beep, then two beeps, and then the text menu screen appears, on which the first option is to start PathPilot. If I choose this option or let it be chosen by the timeout, the screen proceeds to the splash screen and freezes as before.

Inside the cabinet, at this point there are no illuminated LEDs, and the C2 Contactor button is out. Disengaging the E-Stop has no effect.

When I push the Start button, the Machine LED is lit on the panel, the LEDs on the stepper drivers are briefly red and then green, and the LEDs on the Machine Control Board and on Contactor C1 go on, too.

Finally, pushing in the button on the C2 Contactor causes the display on the VFD to light up with "rd 00". Nothing else improves.

I followed the troubleshooting procedures of Table 2.1 without finding anything suspicious:
  • I found wall voltage between wires 102 & 100;
  • Fuse FU3 has essentially no resistance.
  • Both contactors have essentially no resistance across their presumable (vertical) current paths.
  • I couldn't find any loose wires.

I am dead in the water here. Does the story above sound familiar to anyone? Any suggestion will be appreciated..