Graham_Wright
Well-Known Member
As promised, I have attached a few piccies of the sensor dismantled to aid or give courage to any who have a failed unit.
Disassembly is straightforward. Three small screws hold the back cover (and they are small!). This esposes the potentiometer with a three core cable attached. Connections on the original Vishay Spectrol are red and green to the ends and blue to the wiper.
The actuating arm is secured with a roll pin which pushes out fairly easily (I used a 2.5 mm drill and a soft hammer).
There is a centering spring although I don't understand why as the rod attachment to the tiller will overrule it. I suspect it may have been pretensioned as a 180° rotation of the arm is required to realign it. An inclined top to one of the posts permits this (at least before the roll pin is re-inserted as the arm need to lift slightly).
The pot is secured to a disc with three screws but to remove it you will need to detach the cables from the turret pins, snip the cable tie on the inside of the unit and withdraw the cable.
The pot shaft is threaded through two O rings and a fibre washer.
The replacement pot I sourced is from my usual supplier;-
Long Shaft 16mm Mono Mixer Pot, Linear B Potentiometer Various Values ( item: 120941785296 transaction: 1214893256002 )
at a cost of £2.95.
It is long shaft which is just about correct length but has no hole for the roll pin or a flat for location on the actuating arm. These will require a little metalwork but avoid vibrations being transmitted to the track by securing and thus damping the arm with a mole grip or the like. It is carbon track as opposed to the Vishay one which is conductive plastic.
Re-assembly and replacement are a reverse of dismantling (as "they" glibly say!). Although the case is magnetic (=steel) the shaft is not. How suitable it is for different environments, I don't know but my installation is dry below decks.
As my original Vishay pot has performed very, very few rotations, I cannot understand the failure and will offer it to Vishay for their DI department. They may even be interested
.
Disassembly is straightforward. Three small screws hold the back cover (and they are small!). This esposes the potentiometer with a three core cable attached. Connections on the original Vishay Spectrol are red and green to the ends and blue to the wiper.
The actuating arm is secured with a roll pin which pushes out fairly easily (I used a 2.5 mm drill and a soft hammer).
There is a centering spring although I don't understand why as the rod attachment to the tiller will overrule it. I suspect it may have been pretensioned as a 180° rotation of the arm is required to realign it. An inclined top to one of the posts permits this (at least before the roll pin is re-inserted as the arm need to lift slightly).
The pot is secured to a disc with three screws but to remove it you will need to detach the cables from the turret pins, snip the cable tie on the inside of the unit and withdraw the cable.
The pot shaft is threaded through two O rings and a fibre washer.
The replacement pot I sourced is from my usual supplier;-
Long Shaft 16mm Mono Mixer Pot, Linear B Potentiometer Various Values ( item: 120941785296 transaction: 1214893256002 )
at a cost of £2.95.
It is long shaft which is just about correct length but has no hole for the roll pin or a flat for location on the actuating arm. These will require a little metalwork but avoid vibrations being transmitted to the track by securing and thus damping the arm with a mole grip or the like. It is carbon track as opposed to the Vishay one which is conductive plastic.
Re-assembly and replacement are a reverse of dismantling (as "they" glibly say!). Although the case is magnetic (=steel) the shaft is not. How suitable it is for different environments, I don't know but my installation is dry below decks.
As my original Vishay pot has performed very, very few rotations, I cannot understand the failure and will offer it to Vishay for their DI department. They may even be interested
.
Last edited:
.
