Magneta ex Post Office wall clock not running
 

First posting from a newbie! I have a lovely old ex-Post Office clock made by Magneta. When I obtained it in 1980, it was functioning perfectly. It sat for 6 years until I fitted it into out new home, where it ran continuously for 17 years. After another house move, it had languished unused in a loft for a further 16 years. I have finally got around to finding a place to fit it, but it seems as dead as a dodo! It was always a perfect self-starter, sometimes running backwards before correcting itself, and never lost or gained. I have checked all connections and there is 240v at the wires that go into the motor but it just doesn't move, even with gentle prompting through the top of the cover using an insulated plastic rod. All the cogs turn perfectly, along with the hands, but it won't run. Could a synchronous motor lose it's magnetism in storage or could insulation break down within the motor? I would love to get this running again but I'm at a loss as to what to do. Can anyone throw some light as to what the problem may be? I have added some pictures which I hope may be of help. Thanks for reading this missive! :)

Re: Magneta ex Post Office wall clock not running
 

Hi there, and welcome.
Can you hear or feel any magnetic buzz on the motor? If not, it's possible that the stator winding has become open-circuit. It's very fine wire and it doesn't take much for it to corrode and break. If so, there are a few folk on here who will rewind it for you.
By now, it's very probably that it's due for a strip, clean and oil but you should get it running first.

Re: Magneta ex Post Office wall clock not running
 

As the OP has a meter, it would be a good idea to measure the resistance of the motor winding.

Re: Magneta ex Post Office wall clock not running
 

Same principle as the Smith's Sectric movement - the motor can start in either direction but, if it goes backwards, it winds up a little spring which, when fully wound, flicks it back the right way.

The accuracy is determined by the frequency accuracy of the mains supply which, by law, is 50Hz ±0.5Hz. Furthermore, if the supply runs slow when demand is high, it has to be corrected so that clocks are exactly right by 6am the following day.

Normally, there isn't much variation - as I write this the frequency is 50.053Hz. You can always check it for yourself, if you are interested, at http://www.gridwatch.templar.co.uk/

Check the coil for continuity but if it is like the Sectric movements it is most likely that the motor has seized. Just trickling a drop of light machine oil - not WD40! - into the bearings is usually all that is needed.

If the movement is like the Sectric one, the rotor will be very fragile so take care not to apply any force to it. If it shatters, that will almost certainly spell the end for your clock!

Re: Magneta ex Post Office wall clock not running
 

Just a long-shot, but I don't suppose there's a fuse hiding under that paxolin board?

I was caught out that way once with a Sangamo time-switch, a hidden fuse protecting the motor, that blew for no reason other than age, it was a very low value, 32mA I think.

Re: Magneta ex Post Office wall clock not running
 

Hi
Thanks to all for taking the time to reply! :D
There is a little 1amp fuse in the box and it's fine - I checked when I wired the 2 core white flex into it and there's 240v at the terminals.
I'm think the motor must be open circuit as the reading between the pins is infinity on my multimeter.
I left the clock powered up for 5 minutes (whilst in attendance) and there were no sounds at all from the motor and it didn't even get warm.
The motor turns freely if I gently push on the wheels (thanks, Mike!) so it doesn't appear to be seized.
I can't easily see the underside of the motor canister - will it have screws underneath to be able to separate the 2 halves? I'm wary of taking the motor off of the 3 mounting pillars for fear of wheels flying in all directions but I may have to if I can have it repaired / rewound.

Re: Magneta ex Post Office wall clock not running
 

Hi again,

It's looking like the stator winding is open-circuit.
If you take the three screws off the 'spider' nothing else should come off - the two halves of the stator won't be screwed and will just separate. Mark them first.

If the winding is totally gummed up that might need a bit of persuasion.

Careful of the rotor magnet getting any ferrous swarf or filings near it - stick it all in a bag.

Re: Magneta ex Post Office wall clock not running
 

Hi, Mike
OK, thanks very much for the info - will pour a cuppa, put some newspaper on the table and give it a go! Will post what happens! Cheers! :)

Re: Magneta ex Post Office wall clock not running
 

It may be easier to rewind for a low voltage using thicker wire and power the clock from a suitable wall wart ac transformer.

Re: Magneta ex Post Office wall clock not running
 

Hi!
OK - will have a look at what's going on 'under the hood' and go from there. Thanks for the tip :)

Re: Magneta ex Post Office wall clock not running
 

Hmmm.....got the blighter out and it's all surprisingly clean. I reckon there's more chance of Nelson getting his eye back than me being able to separate the motor cases! I have rebuilt a Goldwing no problem but I don't have the small tools to do this motor - it just won't budge! OK, I think Mike Phelan mentioned it may be possible to get it rewound by members from this site? If so, would someone be kind enough to point me in the right direction (other than away ;) )?

Thanks in advance for all your help peeps.

Re: Magneta ex Post Office wall clock not running
 

Two members offering rewinding services are Mike Barker (murphymad) and Ed Dinning. Contact via PM please.

Re: Magneta ex Post Office wall clock not running
 

Thanks very much for the tip on the possible rewinding guys - will PM them tomorrow. Cheers to all! :)

Re: Magneta ex Post Office wall clock not running
 

A big thanks to Mike Barker - motor rewound and clock now purring nicely! Cheers! :)