Accutron watch not vibrating

[jcoffin1981]

__ I am sorry for double posting this, but I put it in the wrong section originally.

I have had a lot of fun learning how these watches work. I have taken a few of these from the dead and got them working again. I was hoping somebody who is experienced with these watches could give me their opinion...

I have a 2180 cal. watch which was stopping and starting. I completely disassembled it, lubricated, cleaned, and reassembled it. The fork now is not vibrating. Somebody who knows their stuff said that a coil may have gone bad in the process. I barely handled them so while this is possible I think it's unlikely. The only issue I can see is that the hack lever keeps popping up when the spring engages. I have some spares so I am going to try replacing the fork and the hack lever.

Perhaps someone knows a common reason for this to happen? Perhaps an area where a mechanical blockage is common or an unintended short in the circuit. I do have the Accutron test set and although the microamperes read high, there is no break in the circuit. I think that it reads high because the fork is not vibrating. Maybe the wrong spacer was used... I dunno.

[lysanderxiii]

Did you check resistance?

The fact operation was intermittent before, makes me think it is the coil.

[jcoffin1981]

It never stopped humming, it was only the rotation of the second hand that stopped. A slight tap and it would start again. This led me to believe that it was a mechanical/lubrication problem problem and was an easy fix. Apparently not.

Lysanderxii, how do I check resistance? This test set does not have that function. I don't have a lot of experience in electronics.

[glenns]

The circuit for the 218 (and 214's, and 224's) is a very basic, if not primitive one. It consists of a transistor (PNP), capacitor, resistor, sense coil and your two main coils.
That's it. Nothing more. Troubleshooting, therefore, is a piece of cake.
Check resistance across the collector of the transistor to its base. This check checks resistance through both main coils. Resistance should be less than 2K ohms. If it is, then you do not have an open in your circuit (in other words, your L1 and L2 coils are good).



The transistor is the round thing labeled, "NPN". the base of the transistor is the wire coming into it from the LEFT. The collector of the transistor is the wire sticking out from ABOVE. A continuity (resistance) check between the two should show resistance in the neighborhood of 2-4K ohms or so. Anything significantly higher and you caused an open in your main coil(s) somewhere; but since you claim to have handled it gently, I doubt this is so.

Check to make sure you have all of your wires to the circuit soldered down correctly.

[jcoffin1981]

Glenns, this is very helpful! Thank you soo much!! I need to find a multimeter that can check this measurement. Will any cheap chinese one work, or do I need to buy a certain model or be within a certain specification? Is it possible some can actually damage the delicate coils? I don't expect you to do my homework, but maybe you can direct me towards a suitable tester. I'm learning as I go along.

Also, what would the appropriate resistance be across the cell coil? Thanks.

[glenns]

Glenns, this is very helpful! Thank you soo much!! I need to find a multimeter that can check this measurement. Will any cheap chinese one work, or do I need to buy a certain model or be within a certain specification? Is it possible some can actually damage the delicate coils? I don't expect you to do my homework, but maybe you can direct me towards a suitable tester. I'm learning as I go along.

Also, what would the appropriate resistance be across the cell coil? Thanks.

There's a comprehensive tester made expressly for Bulova for this movement, but if you think about it, this circuit is nothing more than a transistor amplifier, and a very basic one at that.

Things that can go wrong with the circuit are the same things that go wrong with any transistorized circuit. You said everything was fine and dandy before you commenced your cleaning, then, with everything reassembled, the circuit failed. You also said you took care in the reassembly, Therefore, your problem must be a disconnection somewhere in this simple circuit.
Any ohmmeter will work fine in finding this disconnection; a cheapo unit from Radio Shack is really all that's needed in finding your open.

Facts about transistors: Transistors conduct current in one direction only, and in the direction of current, expect a drop of 600 ohms. The transistor in question is an NPN, which means you apply the POSITIVE lead to the collector and emitter, with the NEGATIVE lead at the transistor's base (refer to my previous discussion on what I mean by a transistor's "base", "collector," and "emitter."). If you look at your movt, the base of the transistor is the tiny wire that's connected to the resistor. And the resistor is that cylindrical thingy with the four stripes on it (one stripe should be silver).

Do NOT! expect your transistor to be at fault; it most likely isn't. However, this information I'm writing to you serves as a basis for checking resistance throughout the whole circuit, keeping in mind what values you should expect to find when checking continuity across the transistor leads.

Make your checks with the battery removed. If you short the battery terminal, expect a lower resistance level from emitter to collector; if you do not short the terminal, your resistance check will be around 2M ohm, keeping in mind your positive probe is on the emitter; negative on the collector.

Coils: If you just want to check the condition of your coils (D1 and D2), connect your multimeter up to the POSITIVE battery terminal and the other test lead to the COLLECTOR of the transistor. Resistance should be under 5Kohms.

[jcoffin1981]

Using the Accutron test set at the positive terminal and the cell strap, the uAmperes are off the chart, so the circuit is not open. Testing the component coil the needle jumps all the way to the right. Maybe the components are weak or partially open? I'm trying to use the multimeter to test resistance of the coil and it's components, but I'm not getting consistent readings. When I figure out how to test it properly and get a consistent reading I will report back. I need to learn more about the electronics of this. I am not a an electrical engineer, and I have no background in this.

Thank you Glenns. I need to learn the exact points to test.

[jcoffin1981]

Okay, so testing from the positive battery terminal and the collector, I am getting a reading of 0.00. I don't really understand. Some numbers flash for a split second, and then it settles at 0.00.

[jcoffin1981]

Okay, so testing from the NEGATIVE terminal I can get ohm readings. I have several movements, and for the coils that work, the cell coil is testing 5.5K and the component coil is testing 4.4. I can also test both of them together and I get just over 10k. It took some tinkering and some practice, but I can now troubleshoot much more easily.

Thank you everyone for your help :)

[jcoffin1981]

I have since fixed this watch. I thought that I would give an update. I actually used the wrong screw in place of the yoke screw. It went through the movement plate and touched the fork which impeded the vibration. I wasted sooo many hours figuring this out. I will post a pic of the finished watch tomorrow.