[pmmunro]

Leon,

Once you have the movement off the front panel, I would recommend a long and careful examination with a good light and some form of magnification - I usually use jeweler's eyeglasses of various magnifications between 2 and 9. It is quite probable that you will be able to see the cause of the obstruction which will help decide the best course of action.

It should be possibly to swing the pointer over the scale with gentle pressure applied to the pointer stem using the bristles of an artists paintbrush which is incapable of applying any harmful force. This should find the exact points at which the movement is sticking.

A close-up examination will give you a better assessment of the nature of the whiskering.

It is possible to take the moving coil with its pivots out of the magnet assembly on these movements but I would recommend placing a keeper across the pole pieces before you do this. I have no service manual information for these movements, so I don't know the official policy on retaining magnetism, but I have successfully dismantled some of these movements without having to have them remagnetised. I'm sure I don't need to tell you to unsolder the outer ends of the hairsprings, but never the inner ends if at all possible.

It will be useful to make a moving coil holder. This is a length of rectangular hardwood with the arrises radiused to fit inside the coil former. Cross drill one end with holes to slide over a length of studding anchored to a heavy base with stop nuts near the top of the studding post. The holder should be long enough to shadow the full length of the pointer, thus giving it protection. Too firm a steady hand could crush the coil former, so the holder helps prevent this.

At the age of your meter, it is quite possible that the small rectangular pivot plates which should be stuck to the fore and aft faces of the moving coil are becoming, or have become, detached; they were originally stuck by shellac. You may find that it is the moving coil wire which is holding the pivot plate in place.

If the pivot plates need to be restuck, you can use the original build up of shellac as witness marks and with luck the pivots will be straight and true, but you may need to make a jig to hold them. This could involve removing the hairsprings by carefully sliding their collets axially along the pivot, having taken careful note of their original orientation with respect to the coil axis. There is also the added complexity of the pointer being free to rotate on the pivot under the restraint of a single wire spring which is quite delicate. A repair using super glue has been reported here and this may well be sound, but my preference would be to keep to the original substance and use shellac. I don't know how the insulation of the wire might react to super glue and if it sticks and the pivots are not in line it could be difficult to realign the pivot without seriously damaging the coil. (Shellac can be bought as "Patent Knotting" from decorators merchants, although the consistency is probably not ideal.

If the whiskers are a metallic salt, they are likely to be from either the tin or the lead in the solder possibly reacting with a constituent of the flux, which should give a clue as to a suitable solvent. In any event, if applied carefully with an artist brush, the common solvents, isopropyl alcohol, pcb cleaner and water will not do much harm. It would be advisable to resolder the connections being careful not to heat the pivot plates too much, or they will come unstuck in any event.

Then you will need to rebalance the movement.

It's just as well you have a steady hand and with all that care you should succeed.

PMM