Kern quartz - an older model?

[AndyDWA]

My wife found this Kern Quartz anniversary-style clock at a secondhand shop a few weeks back. It wasn't working but she bought it for the standard-size glass dome.

We're not really into the quartz models although this becomes number five that we have operating, three of which were picked up for their glass domes but happened to work after a bit of prodding.

Most of the quartz models I see look cheap, even from a distance. There's something about the shiny plastic and the simplistic pendulums that gives them away. But this one is different. The pendulum looks like the real thing - it even has the fast-slow adjuster disc (though I haven't tried it to see if it turns, or adjusts the pendulum, but it can't serve much purpose given the pendulum is purely decorative). From the front, the clock looks convincingly like a wind-up model. As with almost all quartz clocks, it looks like a cheap toy from the back but the plastic body does hide some clever engineering.

The movement is based around an electronic coil and a hairspring balance which can be adjusted via a screw, somewhat like the real thing on other clocks. I don't know the first thing about electronics, so can't tell you much more than the circuit board has just two components, plus the coil.

The pendulum hangs on a suspension wire housed in a top and bottom block and which carries a single-tine "fork" driven by a plastic star wheel. One part which has me fascinated is the bi-directional cork-screw type thread below the coil, that "pulses" the movement by advancing a gear one tooth at a time as it oscillates. I guess it's like an escapement except it pushes teeth, rather than releasing them.

The negative battery terminal was corroded so I MacGyver'd up a replacement and after some messing around and cleaning other parts, it started to tick. Minutes later, the pendulum was swinging just like the real thing.

The clock base has levelling feet and a locking suspension cup. It attracts a magnet, so I assume it's brass over steel. I'm not sure how much polishing it will take but if I can get a shine on it, this will probably be something I'd consider selling to help fund the next "real" clock. I'll need to choose a decent plastic dome for it though.

The clock is quite a bit heavier than other quartz models we have, and I'm guessing it might be a fairly early example. If anyone can guesstimate an age, I'd appreciate the info.

 

[etmb61]

Hi Andy,

This isn't a quartz clock at all. This clock uses a transistor circuit to provide the impulse for the balance wheel. The balance frequency provides the time keeping. The magnets on the balance induce a current into the coils which turns on the transistor, producing a stronger magnetic field in the coil to repel the magnets.

Electronic ATO clocks use the same principle.

A quartz clock uses the crystal frequency to drive a stepper motor for time keeping.

The pendulum is just for looks, but you still need to adjust it to get it rotating properly.

Eric

 

[Tinker Dwight]

Hi Andy,


The pendulum is just for looks, but you still need to adjust it to get it rotating properly.

Eric

Just to be clear, the pendulum on this clock is also for
looks, like a quartz clock. This is a balance wheel electronic
clock.
If the picture you are showing is the balance wheel captured
in mid swing, things are OK. If it is stopped, the balance wheel
is out of beat and needs the hair springs collet adjusted.
With the battery out, the magnet should be right over the coil,
not the counter weight as in the picture.
This clock was made in the 70's when transistors were
available but CMOS integrated circuits for clocks had not
yet been made. Once the CMOS circuits became available,
they started making quartz clocks. The first ones used
4.194304MHz crystals but quickly changed to use the cheaper
32.768KHz tuning fork crystals used in watches.
The transistor used on this is a germanium transistor that
have, for most all applications, been replaced by silicon transistors.
Germanium transistors are known to fail quicker then
silicon because of the method used to create the base/emitter
junction, that is more of a glob of indium melted to the side.
If the transistor has failed they can be had but most all are
NOS ( new old stock ). Some of them are bad from the shelf
so it is a crap shoot. Another source is small table clocks that
often have the same basic ATO circuit, such as some of the
Phinney Walker clocks, labeled "Transistor".
Ops, more than I intended post.
Tinker Dwight

 

[AndyDWA]

Thanks. I have a tendency to refer to all battery clocks as "quartz". I'll have to stop doing that.

I did lower the "fork" a bit as it was only just being caught by the star wheel and the pendulum rotated less than 1/4 turn. It's now doing more than 1.5 rotations and the clock is keeping perfect time so far.

Thanks for the approximate age Tinker.

 

[AndyDWA]

Is it correct to call this an electronic clock, or electric clock?

Also, Tinker, I forgot to mention the photo was mid-swing. The magnets rest correctly. The only thing I'm not sure of at this stage is how to start the clock when inserting a new battery.

With the whole back removed, I can give the balance wheel a small push and it goes from there. But without a push, it just seems to sit there. There is a start-stop lever and the back, but I'm not sure it achieves much. It's not part of any circuit so I assume it just rests against the balance wheel to stop it. Does this mean it should be stopped to move the clock?

I'm now thinking I might keep this one. It's just mechanical enough to hold my interest.

 

[Tinker Dwight]

On similar clocks, I just pick up the clock and
give it a twist. The balance wheel will the take off.
I do have one that has a kicker lever but I don't
use it.
You could call it electronic or these are often called
transistor clocks. These are based on ATO mechanisms
and sometimes called ATO clocks.
There is a piece of aluminum sticking up from the
left that hangs into the balance wheel.
It looks to be not doing anything but actually has a
purpose. These clocks often run with so little loss that
the balance wheel will over swing if allowed to.
They actually work to slow the balance wheel down.
They also help to compensate for differences in friction
of the movement. If the movement adds more drag,
they don't need to absorb as much energy.
The drag is caused by what if often called Farady or
Eddy currents as the magnet swings by the aluminum
piece.
Also, do not oil the movement. It should run fine dry.
The most I ever do is put a thin film of oil on the pivots
while assembling to help stop corrosion. I use a lintless
wipe with a little oil on it.
Not enough that one can see.
The balance wheel may need cleaning. I unpin the hair spring
and remove it from the regulator arm. Then you can loosen
the bottom bearing cup. I then clean the cups with a bushing
stick and some brakeclean.
Other then that, the clock should run for years as long as the batteries
don't leak. If they do leak, immediately neutralize with white vinegar
( assuming you'd use alkaline cells ).
I should note that these can be very accurate clocks, as long
as they are kept in a constant temperature. I have
one movement made by Seiko that I've had running for
two months and is still less then 1 minute off.
You do have to spend some time adjusting them though.
Tinker Dwight

 

[etmb61]

Andy,

It should start on its own when the battery is inserted, but if not, you could lock the pendulum and give the entire clock a slight twist along the axis of the balance wheel.

Eric

 

[AndyDWA]

Thanks. I did wonder about that bit of metal sticking into the balance wheel. I still don't exactly understand what it does, but it's good to know it's doing something useful. Electronics was never my thing, and it's been a long time since I used my high school physics.

A quick shake makes sense for starting.

This was the second battery clock I got going this weekend. The first was a Haller quartz (it really is a quartz), with a plastic "rake" arrangement for rotating the pendulum. I should have taken a photo of the internals.

I have another one which looks like it should go but won't. This one is also an actual quartz, and I can measure pulses on a multi-meter (first time I've ever done that). I got it to "tick" for a very short time, and now it's refusing again. I'll post it in the electric forum tomorrow to see if I can get it going.

These will keep me entertained until I can get my hands on another wind-up. And at least they offer an opportunity to learn something new.

Thanks again.

 

[Tinker Dwight]

More of a single rotate of about 90 degrees, vertically, not a shake.
You can just grab it by the final and rotate your wrist.
You don't need to lock the pendulum. These clocks will not
self start, because they need the motion of the magnet though
the coil to turn on the transistor. No motion, no current.
Tinker Dwight

 

[kirxklox]

Opinion - 270 to 360 would be optimum for rotation. The more work it does, the shorter its battery life.

 

[Tinker Dwight]

Actually, the faster it swings, past the coils, the stronger the current flow.
It is kind of contrary to normal thinking.
My 90 degrees twist was just to start the clock. The balance wheel normally does 360+
degrees total swing. If less something is wrong.
Tinker Dwight

 

[kirxklox]

I was talking about the Pendulum and star wheel. I believe he said it is now rotating 540 degrees?

 

[Tinker Dwight]

I don't think that would be a problem. It is not part of the clocks timing.
Smaller swings would indicate less efficient drive.
Tinker Dwight

 

[AndyDWA]

The only problem I can foresee with a larger rotation is the pressure applied against the rotation of the star wheel on the return of the "fork". The clock is running a bit slow and this may be a cause as the star wheel noticeably slows at this time.

I can raise the fork a little to reduce the back-pressure on the wheel and reduce pendulum rotation to something a little more normal.

 

[kirxklox]

Yepper.

One area I am wondering about is the escapement. I can not tell how it maintains a positive force on the Minute hand.

 

[AndyDWA]

I know more about genuine 400 day clocks than any other type of clock - and I've only just scratched the surface of 400 day clocks.

But, if you mean what I think you mean, then there is a small worm-gear-like device below the balance wheel. This has two angled openings ("scoops") in the "thread" - one pointing clockwise and one counter-clockwise.

As it rotates one way, the bottom scoop picks up a tooth on the nylon gear and pushes it upward. As it rotates back again, the upper scoop pushes the tooth further, leaving the next tooth positioned for the process to repeat. The flat part of the thread ensures the tooth is locked until the next scoop arrives. (As I recall).

It's a joy to watch.

 

[Tinker Dwight]

Do a google for Sully escapement.
Tinker Dwight

 

[Tinker Dwight]

As for the pendulum swing, there are two reasons
for large swing.
One is that the star wheel is pushing harder ( not desired ).
The other is that it is being pushed closer to resonance of
the pendulum ( desired ).
I believe such a large regular swing would indicate the
second.
Tinker Dwight

 

[AndyDWA]

Thanks Tinker. I tried all sorts of searches but it's difficult when you don't know much about clocks in general. This link simplifies it.

I now have to agree on the larger swing. I raised the fork a tiny bit and the swing was small and erratic whereas, with a lower fork, it settled nicely into a ~600 degree rotation.

I also discovered that the star wheel is a light friction fit so, although it stalls a little when the pendulum reverses and presses it, the movement doesn't stall with it.

Unfortunately the suspension spring broke while I was messing with it so I'll have to fish out a regular one and see if it will run with that.

 

[kirxklox]

Use as light a one as you have, and you still may need to thin!

The resonance frequency should approximate the same as the rotation of the star wheel per minute. (Slightly less ?)

The resonance frequency does not change from 90 degrees to 600 degrees rotation. It still operates as a Torsion Pendulum.

 

[Tinker Dwight]

The pendulums frequency is adjustable on this clock.
It might be useful to adjust the fork to miss and see what
frequency it is naturally.
Tinker Dwight

 

[AndyDWA]

I found a remnant suspension spring from a mechanical clock and thinned it down - a lot. I had to judge by feel as I have no tools for that sort of thing.

It's all going again now - so far. I've had to judge the fork height by just watching and seeing how the pendulum behaves. It seems happiest when it's doing at least 1.5 rotations. Much less than this and it becomes erratic.

While I was messing around I decided to polish up the base, so it looks even better now. For a battery clock, this one has been a bit of fun.

 

[kirxklox]

Tool to thin Suspension springs, 2 ice-cream sticks with pieces of Sandpaper glued to one side of each (400 grit). I would not use emery cloth because of the material it is made from.

To decrease the rotation you change the Height of the crutch (Fork) and the position of the Star Wheel has to be adjusted. Timing pulse of the Star Wheel is critical when changing Degree of rotation.

Glad to hear you had a suspension spring you could use.

 

[AndyDWA]

Thanks Sam, that's pretty much the method I used. Although I had to go a little heavier on the sandpaper initially to get the job done faster.

It's now doing two full turns which seems a bit too much as the flag ("fork") is "pinging" off the star wheel under pressure.

Adjusting the flag is frustratingly more difficult than a genuine fork and a fraction of a mm makes quite a difference in how much the star wheel grabs it.

Anyway, I polished it up yesterday and now it looks like someone cares about it. I definitely think these could fool the average enthusiast at first glance.

The only problem is, we bought this for the glass dome to use on one of our standard mechanicals - so now I need to find a nice, clean dome dome for this one again. For now, it has to make do with a cracked and scratched plastic dome.