Graham_Wright
Well-Known Member
There was nothing wrong with it!
I admit to this in case anyone else falls into the same trap.
The actuating arm is keyed to the potentiometer shaft (and roll pinned) and will only fit in one position.
The arm has an index mark to line up with a similar on the housing.
The whole assembly is slightly compliant.
Somehow, the arm managed to override its limit stop (one has an inclined top face) and become 180° out of position. The Vishay potentiometer has no in-built stops. As the assembly was on the bench (= chart table), it was not fixed to the boat, the accidental rotation was not noticed.
The rudder angle indication I saw on the A/P controller went from hard over port to hard over starboard. The DVM indicated a gap in the resistive track. (Is everybody there before me?). This gap is not mid range, it is between one end of the track and the other.
It was only the response to the "centring" spring that caused me to remember it used to bias the arm one way - not to the centre.
Just in case anyone else falls into the same trap (senility helps), check the reference marks line up. It is possible for the arm to be over driven as the whole assembly is slightly flexible. The spring should be biassed hard over, not to the centre.
Confessional finished - please show pity.
(I have apologised to Vishay and Raymarine).
I admit to this in case anyone else falls into the same trap.
The actuating arm is keyed to the potentiometer shaft (and roll pinned) and will only fit in one position.
The arm has an index mark to line up with a similar on the housing.
The whole assembly is slightly compliant.
Somehow, the arm managed to override its limit stop (one has an inclined top face) and become 180° out of position. The Vishay potentiometer has no in-built stops. As the assembly was on the bench (= chart table), it was not fixed to the boat, the accidental rotation was not noticed.
The rudder angle indication I saw on the A/P controller went from hard over port to hard over starboard. The DVM indicated a gap in the resistive track. (Is everybody there before me?). This gap is not mid range, it is between one end of the track and the other.
It was only the response to the "centring" spring that caused me to remember it used to bias the arm one way - not to the centre.
Just in case anyone else falls into the same trap (senility helps), check the reference marks line up. It is possible for the arm to be over driven as the whole assembly is slightly flexible. The spring should be biassed hard over, not to the centre.
Confessional finished - please show pity.
(I have apologised to Vishay and Raymarine).
