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Old 28th Nov 2021, 3:21 pm   #1
vic0239
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Default Smiths Sectric Connector Query

A friend asked me to look at his Smiths Sectric clock as it had stopped working. However, when I connected it up and plugged it in it worked straight away. So thinking there was nothing wrong with it I set out to renew the mains cable and fit an appropriate fuse and generally clean it up a little. However, when I subsequently plugged it in is didnít work! Puzzled by this I did some investigation and it appears that depending on the position of the two pronged connector (it swivels up and down) whether the clock runs or not.

Before I start dismantling the clock is anyone familiar with how the connector is wired inside? Iím thinking that some joint might be being stretched when the connector is moved, but would like some guidance on how to proceed. I donít want to risk damaging the clock if dismantling will not help me fix this issue.

Thanks .. Andy.
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Old 29th Nov 2021, 10:35 am   #2
Mike Phelan
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Default Re: Smiths Sectric Connector Query

Is it not that the male pins on the clock just need to be spread a bit?
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Old 29th Nov 2021, 12:33 pm   #3
Uncle Bulgaria
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Default Re: Smiths Sectric Connector Query

The hinged housing on the one in front of me has a plastic pin which can be pressed out. The conductors are ring terminals with the pin passing through the rings. Springs in the moving piece press the rings of the visible pins up against the rings of the fixed pins that pass into the body of the mechanism.

If you can press out the plastic pin and unsolder the wires from the inside, the whole hinged piece should slide out, as the fixed pins pass through slots in the housing. Watch out for the springs which will ping off.

On this one, the rear housing comes off easily as it has no direct connection to the mechanism, only housing the rear bearing of the rotor.

The photo gives you an idea of the construction. Don't do it this way as you'll break the plastic hinged piece!
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Old 29th Nov 2021, 12:37 pm   #4
vic0239
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Default Re: Smiths Sectric Connector Query

Quote:
Originally Posted by Mike Phelan View Post
Is it not that the male pins on the clock just need to be spread a bit?
Hi Mike. No I don't think so. The connection isn't made by means of a female plug, just an old bakelite terminal connection block which was badly chipped and screwed onto the pins. I've replaced that with a polyethylene equivalent, but had to trip back some of the insulation to ensure a good grip of the pins.
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Old 29th Nov 2021, 12:46 pm   #5
vic0239
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Default Re: Smiths Sectric Connector Query

Quote:
Originally Posted by Uncle Bulgaria View Post
The hinged housing on the one in front of me has a plastic pin which can be pressed out. The conductors are ring terminals with the pin passing through the rings. Springs in the moving piece press the rings of the visible pins up against the rings of the fixed pins that pass into the body of the mechanism.

If you can press out the plastic pin and unsolder the wires from the inside, the whole hinged piece should slide out, as the fixed pins pass through slots in the housing. Watch out for the springs which will ping off.

On this one, the rear housing comes off easily as it has no direct connection to the mechanism, only housing the rear bearing of the rotor.
Thank you very much UB, there is indeed a plastic pin as you say. So, to clarify, the case can be lifted off just by removing the three retaining nuts without disturbing the mechanism?
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Old 29th Nov 2021, 1:05 pm   #6
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Default Re: Smiths Sectric Connector Query

Quote:
Originally Posted by vic0239 View Post
The connection isn't made by means of a female plug, just an old bakelite terminal connection block which was badly chipped and screwed onto the pins. I've replaced that with a polyethylene equivalent, but had to trip back some of the insulation to ensure a good grip of the pins.
The original connector would have indeed been a 2-pin female push-on affair, with screw terminals to attach the flex, enclosed in two Bakelite halves. I've attached a picture of one, just in case you come across one in a pile of old junk one day.

But these get lost, so people improvise with eletricians' "choc bloc" screw terminals, as you've found. These tend to squash the male pins and are even less touchproof than the original connector, so great care should be exercised if you go down this route. It would be wise to make a protective boot using heat-shrink tubing, or even insulating tape or self-amalgamating tape. And if you're doing this, you may as well fit an earth lead too, and make up some kind of cord grip.

Nick.
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Old 29th Nov 2021, 1:11 pm   #7
cheerfulcharlie
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Default Re: Smiths Sectric Connector Query

Could you modify it to take a ubiquitous 'figure of eight' plug and cable?
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Old 29th Nov 2021, 1:13 pm   #8
Uncle Bulgaria
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Default Re: Smiths Sectric Connector Query

Quote:
Originally Posted by vic0239 View Post
Thank you very much UB, there is indeed a plastic pin as you say. So, to clarify, the case can be lifted off just by removing the three retaining nuts without disturbing the mechanism?
That's what happened with this one, and it looks similar to yours. I can't be certain, though if they had a method that worked for assembly one would think they'd stick with it.

The three long brass screws went through the housing into a plate, with the gears on the face side of the plate. The rotor went through a large hole in the plate. The rear end of the rotor spindle went into a bearing in the rear housing. I had to prise the housing off as this had stuck to the rotor spindle with grease. The rotor could be removed and replaced with a straight pull/push as well, as there was only an oblique gear on the face end of the spindle, with another spindle end bearing on the other side.

The housing contained only a ring of metal, presumably housing the armatures, that sat over the rotor so apart from the three screws there was no contact between the rear housing and the mechanism.

Edit: a picture tells...
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Old 29th Nov 2021, 1:15 pm   #9
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Default Re: Smiths Sectric Connector Query

Quote:
Originally Posted by vic0239 View Post
So, to clarify, the case can be lifted off just by removing the three retaining nuts without disturbing the mechanism?
Not usually: the movement is usually screwed to the inside of the case.

You'd have to dismantle the case, take off the hands, remove those nuts/bolts, then remove the movement from the bakelite drum, etc.

EDIT... unless yours is like UB's! There seem to be loads of variations.
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Old 29th Nov 2021, 1:16 pm   #10
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Default Re: Smiths Sectric Connector Query

Quote:
Originally Posted by cheerfulcharlie View Post
Could you modify it to take a ubiquitous 'figure of eight' plug and cable?
No, they're too small.

What you need is an old-style 2A trailing socket, but even these are scarce these days.
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Old 29th Nov 2021, 3:28 pm   #11
vic0239
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Default Re: Smiths Sectric Connector Query

Thanks everyone for the very useful input.

I've attached a better photo of the back of the clock which I think is quite different to UB's and more in line with what Nick was suggesting and what I've experienced in the past working with other clocks.

Returning to my original issue, I wonder if a dab of switch cleaner or isopropyl alcohol in the area of the pin rings might help? It might just be dirt in that mechanism causing intermittent contact. The clock was quite dusty.
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Old 29th Nov 2021, 3:37 pm   #12
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Default Re: Smiths Sectric Connector Query

...or a quick polish with fine emery cloth etc. They're only brass after all.

If this fails, try re-flowing the solder with some fresh solder, or with some liquid PCB flux.
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Old 29th Nov 2021, 5:46 pm   #13
vic0239
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Default Re: Smiths Sectric Connector Query

Quote:
Originally Posted by Nickthedentist View Post
...or a quick polish with fine emery cloth .
Genius! Was just able to slide a thin piece of emery paper into the gap between the pins and give it a good rub while moving them back and forth and cleaned out with some isopropyl alcohol for good measure. Happy to report that the clock is now running with the pins in any position. Thank you for the tip. Just need to secure and insulate the choc-bloc and the jobís done.

Thanks to all Ö Andy.
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