Avometer 8 MK2 Loose AC Cam Wheel - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

sven_swe · 5th Jan 2019, 12:01 am

Hi, no I have never done that. But I am not sure really sure what you mean?

5th Jan 2019, 12:05 am

Hello, I mean this screws.
There are 2 and in the middle is the axis.

pmmunro · 5th Jan 2019, 12:15 am

The jewels are sprung. It should be possible to apply a gentle pressure to the moving coil assembly; the tip of a small artists paint brush would be good. The moving coil will deflect within the jewel screws.

If there is no debris in the air gap, the trouble may be with the pivots and jewels as Aito suggests. Some careful cleaning with isopropyl alcohol using a small brush, even without dismantling, might help. The pivots are not lubricated.

It may be worth checking that there is nothing sticky bridging between the coils of the hairsprings. Spraying the inside of the meter with switch cleaner often leaves deposits on the hairsprings which is why spray cleaning is not a good idea.

If you are really unlucky, a pivot point may be distorted or one of the jewels may be cracked or pitted. According to the service manual the pivots can be restored, but this is in the area of watch repairing. The best hope for replacement jewels is a donor movement.

If you have the skills, experience and facilities, the moving coil can be removed and the pivots can be thoroughly cleaned. The jewels can also be washed out or cleaned as for clocks and watches. The procedure has been described in earlier threads but it must be understood clearly before starting as there is plenty scope for damage.

It is also worthwhile to look very carefully, under good light and magnification, at the pointer and moving coil to check that the moving parts do not foul any fixed part of the structure.

It is possible that the jewel screws have been wrongly adjusted and are too tight; there should just be very slight "shake" within the jewels. Unevenly adjusted jewel screws may have shifted the moving coils assembly axially causing the moving coil or its former to touch the movement frame or the concentrator.

PMM

sven_swe · 5th Jan 2019, 2:16 am

Many thanks for these thorough tips PMM. I will cernaintly not disassemble the unit, I don't have the skills or the equipment for that.
I will check the points that can be done without doing that.

5th Jan 2019, 12:01 am	#21
sven_swe Pentode Join Date: May 2018 Location: Cologne, Germany Posts: 104	Re: Avometer 8 MK2 Loose AC Cam Wheel Hi, no I have never done that. But I am not sure really sure what you mean?

5th Jan 2019, 12:05 am	#22
Guest Guest Posts: n/a	Re: Avometer 8 MK2 Loose AC Cam Wheel Hello, I mean this screws. There are 2 and in the middle is the axis. Attached Thumbnails

5th Jan 2019, 12:15 am	#23
pmmunro Octode Join Date: Jul 2004 Location: Dundee, UK. Posts: 1,813	Re: Avometer 8 MK2 Loose AC Cam Wheel The jewels are sprung. It should be possible to apply a gentle pressure to the moving coil assembly; the tip of a small artists paint brush would be good. The moving coil will deflect within the jewel screws. If there is no debris in the air gap, the trouble may be with the pivots and jewels as Aito suggests. Some careful cleaning with isopropyl alcohol using a small brush, even without dismantling, might help. The pivots are not lubricated. It may be worth checking that there is nothing sticky bridging between the coils of the hairsprings. Spraying the inside of the meter with switch cleaner often leaves deposits on the hairsprings which is why spray cleaning is not a good idea. If you are really unlucky, a pivot point may be distorted or one of the jewels may be cracked or pitted. According to the service manual the pivots can be restored, but this is in the area of watch repairing. The best hope for replacement jewels is a donor movement. If you have the skills, experience and facilities, the moving coil can be removed and the pivots can be thoroughly cleaned. The jewels can also be washed out or cleaned as for clocks and watches. The procedure has been described in earlier threads but it must be understood clearly before starting as there is plenty scope for damage. It is also worthwhile to look very carefully, under good light and magnification, at the pointer and moving coil to check that the moving parts do not foul any fixed part of the structure. It is possible that the jewel screws have been wrongly adjusted and are too tight; there should just be very slight "shake" within the jewels. Unevenly adjusted jewel screws may have shifted the moving coils assembly axially causing the moving coil or its former to touch the movement frame or the concentrator. PMM Last edited by pmmunro; 5th Jan 2019 at 12:16 am. Reason: typographical error correction

5th Jan 2019, 2:16 am	#24
sven_swe Pentode Join Date: May 2018 Location: Cologne, Germany Posts: 104	Re: Avometer 8 MK2 Loose AC Cam Wheel Many thanks for these thorough tips PMM. I will cernaintly not disassemble the unit, I don't have the skills or the equipment for that. I will check the points that can be done without doing that.