Subject: Re: [sloan-25mlog 3867] 2.5m obslog 20180201 (SJD 58151)
From: John Downey
Date: Fri, 2 Feb 2018 06:25:23 -0700
>=20
> During the cart change to cart 2 it was found that the North slit head =
door=20
> shows "closed" status, all the time. Also, the hand paddle stopped =
working
> properly in the Auto side: there is no lights on the paddle. neither=20=
> weight indication.=20
> JohnD switched the hand paddle to the Manual side. Light are on there.=20=
>=20
> After changing to cart 2 telescope was unable to move the AZ axis.=20
> Interlock shows the wind_az_plc_perm red bit it set.=20
> We power cycled amplifiers and the WB knife switch, it did not help.
> Called JohnD on site. =20
> JohnD traced the problem down to a bad wire in the 15-degree sensor =
block.=20
> The wire was replaced.=20
> 03:40Z JohnD replaced the bad wire in the 15-degree sensor block.=20
> Telescope now can move, went to the field. =20
>=20
For the record, the problem was the hall effect sensor for the retracted =
position of the 15 degree stop (its molded on the end of a long piece of =
wire).  Without both hall effects reporting either on or off without =
contradicting the other one, the PLC reports an error condition and will =
not grant the windbaffle az permit (among others).
The worrying thing about this is that the slithead door sensors are of =
the same type and also work with the PLC.  Unfortunately they are also =
much harder to get to, but I think we can work around that.=