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Discussion Starter · #1 ·
I have been meaning to make one of these for sometime, but my memory was jolted by some talk on this forum about the subject.

After looking around they all seemed to be designed around the old mains voltage to 6v door bell transformers and a carbon rod.
So I purchased the following:

Transformer 2 x 115v to 2 x 6v 12VA
Carbon Graphite Rod
Fused IEC mains inlet with neon switch
Push to make switches x 2
Self adhesive feet 22 x 10 mm
Sleeved gromits 6.3 mm
Assorted heat shrink
Project Box, ABS, Black, 150 x 100 x 55 mm
Hookup wire
Crocodile Clip

I connected the transformer to have the 2 x 115v in series to give 230v and took the outputs so I could use either just 6v or 12v (works out at 7v and 14v with the mains here). One gromit is for the wire leading to the carbon rod (wire is just wrapped around the rod then soldered), the other is for the wire attaching the crocodile clip and the third is just to hold the rod when not in use.

It works by interrupting the 6v line with a crocodile clip making contact to the metal on the dial (the other claw contacting the dial is protected with heat shrink so it won't mark the painted side) and the carbon rod. This rod which I shaped in to a V with a notch cut out contacts the dial dial foot which will be held in a pin vice. Completing the circuit between the new dial foot and dial causing arching and quick instant heat melting the solder without giving time for the heat to damage the painted dial.

I wired mine with two buttons, so pushing one gives 6v and pushing the other gives 12v, I decided on this instead of just 6v as a belt and braces option as I often work on pocket watches with thick dial feet and dials.

I hold the dial in a movement holder to keep it still while placing the pin vice and rod against each other with a tiny bit of solder and flux around the edge. Then push the button, it sparks a little and quickly melts the solder, providing all surfaces are clean and oxidation free.







 

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video of this in action would be nice.
 

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Discussion Starter · #3 ·
video of this in action would be nice.
Sorry not got a video camera, have a Rado on my bench with both feet snapped off so will photograph that being done, will be a few weeks till it gets done though.
 

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Well done, the whole thing looks very professional and put together with care.

I would have thought that you would need a nice filtered DC current to get the results, along the lines of a welder, but on a smaller scale of course.

Looking forward to photo's of the results.
 

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Discussion Starter · #5 ·
Well done, the whole thing looks very professional and put together with care.

I would have thought that you would need a nice filtered DC current to get the results, along the lines of a welder, but on a smaller scale of course.

Looking forward to photo's of the results.
Thanks, will update when I get around to the watch. I understand what you are saying with the DC current, but just the few test bits I did with AC worked, but I have to move the carbon rod to arc across a small gap by either shaping the dial foot to have a small gap for the solder or moving the rod just away from the surface.
Might knock up a simple ac to dc converter with some diodes and give that a try to see if it improves things.
 

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Discussion Starter · #6 ·
Small update, I cut the carbon rod much shorter which has really helped. The 6v and 12v option I decided to get rid of and have gone for 6v only, but using both 6v taps in parallel to increase the amps. This way works really well.

I have not tried building a simple rectifier yet as the AC is working fine and not arcing.

Flux is important and touching the rod to the foot first then turning it on to heat it up otherwise you will get arcs and burn the metal discolouring it.

Will update in a bit when I do the first customers dial with pictures.
 

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Hi

I had the same idea last month and built this using a 13,8V max 7A power supply. But it seems that there is not enough power as only some spark and some smoke appears but not enough heat. Need a bit of help here to get it working. Is it just that I need more Amps?

Best regards
Dirk

Electronics Technology Electronic device Wire Electronics accessory
 

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Alexsm,
Please conduct any further communication with Cougarnaut regarding sales of his machine via PM. This forum is not for selling/buying.
Thank you.
Samantha
 

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Hi,

Not something I've needed but maybe a good way to do this is just to use a variable bench power supply unit where both the voltage and current can be precisely controlled. These power supplies can be set to current limit.

TENMA - 72-10480 - Bench Top Power Supply, 0-30V 3A with Single Output | CPC UK

Not much for a 3A max version and for a little more you can have the 5A version.

Then all you need is a platform. Connect the bench PSU with 4mm plugs and this would be a powerful solution and you would have a good PSU for any other work. etc.

I think I would try this - maybe?

Tom
 

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Interested in building a machine myself. Can you tell me what th 2x115 volt primary voltage means. I mean I know the transformer works on 115 volts..but why is it twice that amount of voltage? The secondary meaning it has two separate 6 volt terminals? Thanks in advance!
 

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Interested in building a machine myself. Can you tell me what th 2x115 volt primary voltage means. I mean I know the transformer works on 115 volts..but why is it twice that amount of voltage? The secondary meaning it has two separate 6 volt terminals? Thanks in advance!
The OP is in the UK, where we have proper mains voltages. Using 2x115v primaries in series gives the appropriate 230v input.
Dave
 

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Man..You folks can really get a shock off of that much voltage. I'm not sure what type I would need here in the USA using 115 volt transformer. Is there a minimum VA that is allowed?
 

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