Sticking indicator on bellset 20

[Dave Moll]

I have a bellset 20, which I have wired up and found to be electrically in fine fettle. It does, however, have a minor, but rather annoying, mechanical problem:

When I lift the handset on the extension 'phone, the flag on the bellset comes up saying "engaged" as it is supposed to, but when the solenoid holding it up retracts on replacing the handset, the flag remains up until either I manually push it back down again by opening up the box and pressing on the shaft, or by jolting it on closing the box back up fairly hard.

I assume that the flag is supposed to reset itself simply though its own weight once it is no longer being held up by the solenoid, but it seems to be sticking on something once it is in the display position - though I can't see anything obvious. Any thoughts would be appreciated before I resort to dismantling the indicator unit.

[Dave Moll]

I have now detached the indicator mechanism from the cabinet, thus giving me a better view of what is happening. It is the armature of the solenoid itself that is not retracting once power is removed. It looks as though the problem isn't mechanical after all, but that the solenoid coil is somehow holding onto the armature - given that manually operating it without applying power to the coil doesn't cause the same problem. Any suggestions?

[ThePillenwerfer]

Looks like an interesting bit of kit, Dave.

As for what ails it all I can speculate is if the armature has picked up some permanent magnetism.

- Joe

[Dave Moll]

I'm pleased to report that I have now received a suggestion from a different quarter to circumvent the problem - consisting of the ultra-high-tech solution of placing a sliver of PVC tape between the armature and the end of the solenoid. And it has had the desired effect.

Yes, Joe, I too had reached the conclusion that it was a case of residual magnetism. The slight gap between solenoid and armature has overcome it, though I'm no closer to understanding how the problem has occurred, nor how to address it properly rather than what is, admittedly, something of a "bodge".

[mickash]

Would a tape head degausser do the trick?

Michael.

[AC/HL]

Originally Posted by Dave Moll

admittedly, something of a "bodge".

Had they still been in service, this would have been called a service bulletin, not a bodge.

[Dave Moll]

Very good, Bill. That brightened my morning!