I've had an intermittent fault on the Tool Turret for a while - it seems to come and go but I convinced myself that it was heat related. Manifests itself as the SMCC card and or the 820T controller reporting it is at a wrong tool location when a tool change is commanded. Leave it alone for half an hour and the fault clears only to come back later.
So today I've been having fans pointing at things and trying in vain to locate the issue, until . . .
. . . the fault came on, and I happened to read the data word on the controller that indicates tool position, and blow me the least significant bit was missing! Now there is a four way proximity switch in the turret that I'd looked at before and all seemed well, but while the fault was on I was able to chase the wiring and the issue was definitely the proximity sensor - so pull it out. Shame really as having been in here before I'd already sealed the chamber with Blue Hy-Lo-Mar sealant.
Out it came and certainly bit zero is different from the others. Unloaded it's giving about 7 volts not detecting, but goes correctly to about 24 volts when detecting, whereas a good channel sits at about 2 volts and also goes to 24 in the presence of a spanner.
Loaded with 4K7 ohm to ground, so about 5 mA load, both good and bad go close to zero undetecting, but the bad channel stays at about zero in the spanner test.
So the hunt is on for a replacement. I could if necessary make up a bank of four individual proximity sensors but I'd rather avoid that if possible
Incidentally in previous posts I've referred to this sensor as made by Euchner - it's not it's a Balluff BES 516 B4 T0B-08-650 in case you have one in the odds box
