A while ago I could buy a Junghans Chrono Vox S cheaply because it was “a bit noisy”. This was a gross understatement as every minute it produced a terrifying screeching sound.
After opening the case it was clear I was not the first one in there. Someone had drilled four (!!!) holes in the motor in order to add oil. And as this did not work he/she gave up and did not even bother to seal the holes, so it was still leaking oil. Oh joy!
To examine the issue I opened up the motor. My “tapping on the rim of the case” trick did not work, but using a knife I was still able to slowly wedge the lid out, albeit with a little damage.
Holding the now naked mechanism in the field of the coil I could test what was going on. One of the gears had developed quite some lateral play and under load (typically every minute) it moved sideways and came in touch with a gear it was not supposed to. This caused the screeching noise.
At this point I had not much hope on a successful repair, but with nothing to loose I decided to go where I had not gone before and open up the gearbox. This works much the same as opening up a Copal gearbox, only smaller: drill out the three rivets just until you are able to lift the plate. To protect the vulnerable rotor while doing that work I made a temporary stand out of a piece of wood.
Now the worn out pivot point was clearly visible. I then did a bit of reading on the internet to learn how “real” clockmakers solve this issue. They apply a technique called “rebushing” which means drilling out a larger hole where the pivot hole was and pressing in a new brass bushing. A suitable bushing I found on AliExpress: https://www.aliexpress.com/item/3305...d=4rBCqbE0z3JW
I then increased the hole size using a drill and needle files. This is painstakingly slow and precise job as you need to make the hole with the exact correct size and position. In the end I got a bit impatient and thus ended up with a loose fit. Used a little epoxy glue to correct that mistake.
Final steps: reassembling, lubricating and sealing up the holes in the case with epoxy glue.
The motor has been running fine and silently for about a week now!
And I learned a new skill (only hope I don't need it too often).
After opening the case it was clear I was not the first one in there. Someone had drilled four (!!!) holes in the motor in order to add oil. And as this did not work he/she gave up and did not even bother to seal the holes, so it was still leaking oil. Oh joy!
To examine the issue I opened up the motor. My “tapping on the rim of the case” trick did not work, but using a knife I was still able to slowly wedge the lid out, albeit with a little damage.
Holding the now naked mechanism in the field of the coil I could test what was going on. One of the gears had developed quite some lateral play and under load (typically every minute) it moved sideways and came in touch with a gear it was not supposed to. This caused the screeching noise.
At this point I had not much hope on a successful repair, but with nothing to loose I decided to go where I had not gone before and open up the gearbox. This works much the same as opening up a Copal gearbox, only smaller: drill out the three rivets just until you are able to lift the plate. To protect the vulnerable rotor while doing that work I made a temporary stand out of a piece of wood.
Now the worn out pivot point was clearly visible. I then did a bit of reading on the internet to learn how “real” clockmakers solve this issue. They apply a technique called “rebushing” which means drilling out a larger hole where the pivot hole was and pressing in a new brass bushing. A suitable bushing I found on AliExpress: https://www.aliexpress.com/item/3305...d=4rBCqbE0z3JW
I then increased the hole size using a drill and needle files. This is painstakingly slow and precise job as you need to make the hole with the exact correct size and position. In the end I got a bit impatient and thus ended up with a loose fit. Used a little epoxy glue to correct that mistake.
Final steps: reassembling, lubricating and sealing up the holes in the case with epoxy glue.
The motor has been running fine and silently for about a week now!
And I learned a new skill (only hope I don't need it too often).
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