By Larry Klein*

SIMPLE FIX: The Fusible Link

This clock fix is pretty straightforward, but you have to have steady
hands. 99 times out of 100 the problem with these clocks is that the fusible link has burned out and it needs to be reconnected. This is of course only true with the electro-mechanical clocks, not the quartz ones - if the quartz ones go, you might as well toss `em.

The fusible link will blow EVERY TIME if you connect the clock backwards, EVEN FOR AN INSTANT, so don't do that. The POSITIVE (+) connection is the one coming out the center of the back, the NEGATIVE (-) is to the chassis of the clock. That positive power is on ALL THE TIME, so if you really want to be sure, pull the clock fuse until all the connections are, well, connected.

If connecting it backward wasn't your problem, it's probably really better to take the whole thing apart and clean it than to just fix the fusible link, cos odds are that the clock being dirty caused the link to blow. That's not a job for the faint of heart, though, so the first part here is just for fixing the fusible link.

To fix the link, take the back off the clock - it's held on by three nuts, one of which is probably inside a small gray plastic case - a "factory seal" - if the clock has not been molested before now. Just grab the plastic around the nut with a small pliers and squeeze it - the top will pop off and you can see the nut inside. I just crack those things off and toss them.

With the cover off, you can see the mechanical works, in the midst of which will be an electrical coil - look for copper windings. That coil is the electromagnet that winds the clock when it runs down - the spring in it is good for about 5 minutes, then a set of contacts closes and energizes the coil, which pulls the spring back again. At this point you can figure out which part turns to wind the clock, and you can turn it a little and see if the clock starts to run. If it doesn't start on it's own just by winding it, then it really needs a cleaning and the fusible link fix alone isn't going to work.

Assuming it starts on it's own, and the fusible link is just busted  on one end of the electrical coil, there is a little finger of metal that is supposed to be held by a rivet onto the chassis of the clock. You can probably still see the remains of the rivet, and see where the finger of metal belongs. This "rivet" is actually made of a low-temperature solder, so that if for whatever reason the contacts energizing the coil don't immediately open (clock is stuck, etc.), the "rivet" melts and the power to the coil is cut off. This is preferable to starting a fire in your dashboard!

What I do is, rather than try to re-solder the connection (the solder is so ridiculously low-temperature that it just runs everywhere if you try it with a normal iron), I pull out the remains of the rivet and carefully re-form it into a new rivet by mashing it this way and that with a jeweler's pliers. It's not as difficult as it sounds - except for it being TINY (the head is about 2.5 mm across), it's just like straightening a nail. When I have the rivet shaped, I simply put the finger of metal back were it belongs (you have to hold it there - it's spring-loaded to pull away), line up the holes (you'll know them when you see them) and put the rivet through the holes. Then gently mash the point down into a headed rivet again, so it doesn't fall out. The electrical connection is restored! You might clean the electrical contacts for good measure with alcohol (they get pretty sooty, which is what gunkifies the clock in the first place), and put the whole thing back together. If you're considering oiling it, I just use a light oil (like gun oil) and only lubricate the shafts of the BIG gears, not the little oscillating balance wheel; it's jeweled and lubing it just gunks it up. Use oil VERY sparingly - like applied with a toothpick.

If you decide take the clock apart to give it a real cleaning, be prepared to maybe STILL have it not work afterward. It's so delicate that my success rate (and I have some experience) is about 70%. A well-known and S6R-friendly store owner gave me 5 clocks to do for him, and including the 3 or 4 I had laying around, I was able to - just barely - give him back 5 perfect ones. Like the one in my car (which has been working perfectly for two years now), they worked great when I was done with them.

The following is not for the faint of heart, weak of eye, or unsteady of hand:

Taking the Clock Apart

The first thing you must do, and this is an ABSOLUTE must, is look at the clock carefully, figuring out how it works and what is connected to what. If you start to take it apart without understanding where everything goes and why, then getting it back together again will be NO pic-a-nic. Diagram if you have to. Understand that the larger gears are closer to the power source (the spring, not the electrical connection) and the power in transferred from there through smaller and smaller gears leading down to the escape wheel (the plastic gear with the funny teeth), balance wheel (the wheel that oscillates back and forth) and fulcrum (rides the funny teeth on the escape wheel and goes back and forth across the balance wheel).

It sounds really complicated, but there are only 3 gears in the time train of the clock. The time train connects the power source to the power release - the balance wheel, which lets the power out in even increments (the ticking), and thus makes the clock accurate. There are a couple of other gears that gear down the hour hand so that it runs at 1/12th the speed of the minute hand, but those are separate and easy to deal with.

The nuts that hold the back on screw onto shafts that run through the clock from front to back. Remove the setting knob, the screws holding the front on, remove the hands and face, and remember (or better yet, diagram) the arrangement of gears that connect the setting knob shaft to the works. It is a pain to get that back together if you have to figure it out.

After the face is off, you'll see three spring clips that hold the works to the chassis - these have to come off, and they're a b*tch. Don't' lose them - if you bent them up don't worry about it; straighten them so you can use them again.

Next, if you haven't already done so to deal with the fusible link, on each shaft where a nut was holding on the back of the clock there is another nut that was under the cover (sort of a jam nut situation before you took the back off). There are three; removing them will allow you to take the electrical assembly in it's entirety off of the clock.

You can also, at this point, pry off the silver-colored pin that holds
the hand reduction gears together on the other end of the clock. It's
holding one of the brass gears on the front (behind where the face was) on; it just prys off. That will let you take off the hour-hand gear and the transfer gear; to get the minute-hand gear off you'll need to pry up and rotate the bushing that holds one end of the power gear. The power gear is the one that pokes through the top plate and powers these three front gears. The bushing in question has a little plastic tab on it made specifically for grabbing and lifting so you can rotate is and free the minute-hand gear. Don't lose the spring washer under it.

This leaves you with the works in it's bare-bones state - it's pretty easy now to see how it works.

Taking the rest of the clock apart is fairly obvious - the shafts that
hold the plates together are threaded on the ends - just grab the hex at the base of each shaft and turn it.

Obviously, remember where everything goes.

Use alcohol for cleaning - I soaked all the mechanical bits for awhile. I DID NOT SOAK THE ELECTRICAL BITS, and I would recommend against it (but without any real authority). Of course, be very careful of the hairspring - the tiny spring (thickness of a hair) that causes the balance wheel to oscillate. When you take the clock apart, the balance wheel will be held on by nothing but that tiny spring, so be careful. I, as a rule, do not take apart the hairspring or fiddle with the tightness of the balance wheel (the adjustment screw has lock-tite on it, and I leave it) because I don't have instruments or data for getting> that stuff back in tune.

Assembly is the reverse of dismantling - with the following note: the shaft that regulates the speed of the clock (a shaft that rides against a half-moon-shaped plate), does not go in until last - the spring that retains it goes in before it. Position the spring (it looks like a little clip) in the pocket where it resides, then push the setting shaft in until it snaps into place - the spring causes the groove in the shaft to engage the half-moon plate. Also, remember when putting the electrical assembly back in place (on the back of the works) to hold the spring-loaded pall out of the way of the ratchet gear (the pall lets the gear only turn in one direction, so you can wind the clock). You saw how that worked when you wound the clock before you started all this nonsense.

If none of this makes sense, you obviously aren't in the middle of a tear-down, and perhaps you don't want to be.

If you've done everything right, not overdone it with the oil, and haven't damaged any of the itty-bitty critical parts while going through all this nonsense, the clock should run when you manually wind it. Every time. Starting by itself (though sometimes I've had to give it a shake the very first time). When testing it, make sure to let it run> completely down a few times, in addition to connecting it to at least a 2 amp 12v power source to have it self wind.


Hope this has been educational and not too painful. Doing it without diagrams has been a challenge...


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