06-06-2013, 09:55 PM
Folks,
Went to the local auction last night and picked up a Schatz ATO clock for £2 (not working).
These clocks followed on from the clumsy and unreliable 400 day mechanical clocks. They used the same baseplate, frame, dial and dome as the earlier, mechanical models. Perhaps they 'used up' the surplus stock of parts as far as possible.
The Schatz 400 day mechanical clocks are common, unreliable (in my opinion) and do not keep accurate time. They suffer damage if moved quickly or knocked and the key was often lost as it was only used once-a-year. I have several of these mechanical clocks and it is hard to get any of them to run for a year, let alone 400 days.
The early electronic version comprises of two separate assemblies powered by the same 1.5V battery ('C' cell). The clock is a two-transistor ATO movement which is not self-starting. It is a fairly accurate timekeeper once adjusted properly.
The rotating, 4-ball pendulum is for decorative purposes only and is not used for time keeping. This assembly is also a two-transistor circuit connected around a pair of coils. The pendulum has a pair of permanent magents fixed to it which pass either side of the coil assembly. One coil is a sensing or trigger coil; the other is a driven coil which is switched on as the trigger coil is energised, the resulting current generates a magnetic field which repels the pendulum to keep it moving.
So what was wrong with this clock? As usual, a rotten battery had turned the negative terminal into an insulator. Cleaning with a brass wire brush on a 'Dremel' restored the connection and 1.5V could now be measured on the clock and pendulum pcbs. However, the clock would not run, so I check and found one transistor was short circuit b-e. These early silicon types were not particularly reliable, especially if the battery had been inserted the wrong-way round at some time. The transistor was changed for a modern type and the clock ran well, keeping good time too.
The pendulum unit would not turn properly and upon closer examination, one of the permanent magnets had become detached and was sticking to the other magnet. I've seen this before and think the 50+ year old glue is no match for the attraction of two magnets close together and that which is least-stuck jumps across the gap and stick to the other magnet. I removed both magnets and used Araldite (yes, you can still get it - just!) to fix them back into their correct positions, remembering to fix one magnet and let it harden before doing the same with the other one, to avoid a repeat perfomance of the original fault.
Ok, all done and the unit was reassembled and tested on the bench. This particular design accurately mimics the original pendulum movement with a period of several seconds. Other makes are rubbish and the pendulum goes flying round like a kid's toy.
The pendulum unit worked fine on its own, but slowed down and stopped when the weighty pendulum itself was fitted. I dismantled it again and cleaned and polished the bearing surfaces, but it still stopped after 10-20 seconds. It seems there is a lack of power and more energy needs to be sent through the repulsion coil. A capacitor is discharged through the transistor and coil, so perhaps this has lost some microfarads over the years. Unfortunately, all the circuits are similar, but slightly different so I will have to trace out the connections around the pcb and make a drawing. The output transistor may have become leaky or lost gain so I will have a look at this too.
I suppose the point I am trying to make is that there is little interest in these clocks because they do not 'wind-up'. I have only ever seen around 3-4 of these clocks compared to several hundred mechanical clocks from the same era. Ok, they aren't everyones' cup-of-tea, but to be honest, I've spent many hours trying to get the mechanical type working again..... all for another couple of months before it packs up again.
I've posted some pictures of the bit as and pieces in case anyone is interested and will post one of the completed clock once i've solved the pendulum problem.
The first two pictures are the ATO clock movement. Notice the pair of coils under the balance wheel and my nice new shiny transistor.
The third picture is the pcb as removed from the pendulum assemby. You can see the double windings of the coil - one red winding and one green winding.
The fourth picture shows the dismantled pendulum assembly.
The fifth picture shows the repaired rotor with the magnets fixed in the correct positions. The coil in picture three passes between the magnets as the rotor moves.
I hope that helps should anyone decide to buy on of these clocks. You will need some basic clock repair skills as hairsprings and balance wheels are involved.
Thanks for reading.
Went to the local auction last night and picked up a Schatz ATO clock for £2 (not working).
These clocks followed on from the clumsy and unreliable 400 day mechanical clocks. They used the same baseplate, frame, dial and dome as the earlier, mechanical models. Perhaps they 'used up' the surplus stock of parts as far as possible.
The Schatz 400 day mechanical clocks are common, unreliable (in my opinion) and do not keep accurate time. They suffer damage if moved quickly or knocked and the key was often lost as it was only used once-a-year. I have several of these mechanical clocks and it is hard to get any of them to run for a year, let alone 400 days.
The early electronic version comprises of two separate assemblies powered by the same 1.5V battery ('C' cell). The clock is a two-transistor ATO movement which is not self-starting. It is a fairly accurate timekeeper once adjusted properly.
The rotating, 4-ball pendulum is for decorative purposes only and is not used for time keeping. This assembly is also a two-transistor circuit connected around a pair of coils. The pendulum has a pair of permanent magents fixed to it which pass either side of the coil assembly. One coil is a sensing or trigger coil; the other is a driven coil which is switched on as the trigger coil is energised, the resulting current generates a magnetic field which repels the pendulum to keep it moving.
So what was wrong with this clock? As usual, a rotten battery had turned the negative terminal into an insulator. Cleaning with a brass wire brush on a 'Dremel' restored the connection and 1.5V could now be measured on the clock and pendulum pcbs. However, the clock would not run, so I check and found one transistor was short circuit b-e. These early silicon types were not particularly reliable, especially if the battery had been inserted the wrong-way round at some time. The transistor was changed for a modern type and the clock ran well, keeping good time too.
The pendulum unit would not turn properly and upon closer examination, one of the permanent magnets had become detached and was sticking to the other magnet. I've seen this before and think the 50+ year old glue is no match for the attraction of two magnets close together and that which is least-stuck jumps across the gap and stick to the other magnet. I removed both magnets and used Araldite (yes, you can still get it - just!) to fix them back into their correct positions, remembering to fix one magnet and let it harden before doing the same with the other one, to avoid a repeat perfomance of the original fault.
Ok, all done and the unit was reassembled and tested on the bench. This particular design accurately mimics the original pendulum movement with a period of several seconds. Other makes are rubbish and the pendulum goes flying round like a kid's toy.
The pendulum unit worked fine on its own, but slowed down and stopped when the weighty pendulum itself was fitted. I dismantled it again and cleaned and polished the bearing surfaces, but it still stopped after 10-20 seconds. It seems there is a lack of power and more energy needs to be sent through the repulsion coil. A capacitor is discharged through the transistor and coil, so perhaps this has lost some microfarads over the years. Unfortunately, all the circuits are similar, but slightly different so I will have to trace out the connections around the pcb and make a drawing. The output transistor may have become leaky or lost gain so I will have a look at this too.
I suppose the point I am trying to make is that there is little interest in these clocks because they do not 'wind-up'. I have only ever seen around 3-4 of these clocks compared to several hundred mechanical clocks from the same era. Ok, they aren't everyones' cup-of-tea, but to be honest, I've spent many hours trying to get the mechanical type working again..... all for another couple of months before it packs up again.
I've posted some pictures of the bit as and pieces in case anyone is interested and will post one of the completed clock once i've solved the pendulum problem.
The first two pictures are the ATO clock movement. Notice the pair of coils under the balance wheel and my nice new shiny transistor.
The third picture is the pcb as removed from the pendulum assemby. You can see the double windings of the coil - one red winding and one green winding.
The fourth picture shows the dismantled pendulum assembly.
The fifth picture shows the repaired rotor with the magnets fixed in the correct positions. The coil in picture three passes between the magnets as the rotor moves.
I hope that helps should anyone decide to buy on of these clocks. You will need some basic clock repair skills as hairsprings and balance wheels are involved.
Thanks for reading.
