Diagnostic help needed: Bulova 242 Quartz Mechanical

[PastorChris]

I recently picked up a late 1970's Bulova Accutron Deep Sea 19810 "devil diver" with the Caliber 242 movement. It is a very impressive movement in terms of its modular design and I would love to see it running again. 

I have taken apart the movement, cleaned the mechanicals and put it back together with everything running smoothly when manually manipulated. 

I installed a fresh battery and the stepper motor will click twice in one direction, not enough to move the seconds hand, and then reverse direction for a couple of clicks. This goes back and forth a bit then stops. 

Just to be sure I removed the hacking lever and checked the mechanicals and cannot find any fault. So I am guessing this is a problem with the stepper motor.

I would appreciate hearing if:

a. Does anyone have any further ideas about what might be wrong/ what I might try

b. Does anyone have a 242 movement or stepper motor that they would sell me for this project?

I have searched the web for a motor and cannot find one in stock, but that is not much of a surprise.

Thanks in advance.

 

[Graziano]

Hi there, here is the manual for the movement in case you need it. Apparently the movement was made by Citizen and assembled in Switzerland for Bulova. 

Graziano 

242.pdf

[HectorLooi]

Hi Pastor, long time no see. Welcome back. 

What an interesting movement. I've never seen one before. I do not see the driver circuit for the stepper motor. Is it under the name plate?

The fact that the motor is capable of twitching is a sign that the motor might be ok. If you can test the electrical resistance across the tracks of the stepper motor, you can confirm this. 

I would suspect that it's the driver circuit at fault. I don't see any pcb for the 2423.10 on ebay at the moment.

Good luck.

I just trawled eBay and found that there are 2423.11 pcbs. I'm not sure if it's compatible with a 2423.10.

https://www.ebay.com/itm/265162608779?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=BbEol4SXTyy&sssrc=2349624&ssuid=v36TsHWBSw-&widget_ver=artemis&media=COPY

[Kalanag]

The movement has no sensor to find out whether the train moves or not. The only way is sensing the stepper current. Could be that the pcb feels to much current drawn by the stepper. To be sure that there is not to much drag in the train I would try to operate the stepper without wheels (or with just one wheel).

Edited June 2, 2022 by Kalanag

[ChrisRobinson]

There could be something jamming the motor?  They do tend to attract any steel particle or shaving, so you might have to remove it and inspect carefully.  I agree that if it's moving at all, the motor might actually be OK.

[PastorChris]

Good advice here and it is much appreciated. Thanks to @Graziano's PDF file I have ordered the proper tool to remove the 5 spoke drive wheel so I can check to see how the stepper motor works on it's own, according to @Kalanag. Thanks also to @HectorLooiand @ChrisRobinsonfor their suggestions. I will continue testing along those lines and report back.

[JohnR725]

On 6/1/2022 at 6:22 PM, HectorLooi said:

The fact that the motor is capable of twitching is a sign that the motor might be ok.

yes twitching seems nice but stepping would be better.  the problem is the stepping motors go bad and then they no longer step.

On 6/1/2022 at 6:22 PM, HectorLooi said:

I do not see the driver circuit for the stepper motor. Is it under the name plate?

it's hiding on the bottom side of the circuit board its there is just hiding.

On 6/1/2022 at 11:39 PM, Kalanag said:

o be sure that there is not to much drag in the train I would try to operate the stepper without wheels (or with just one wheel).

yes that's one of the standard tests to verify the stepping motor remove the wheel that it drives put a felt pen Mark works on the gear and see if it rotates.

Then ideally on a quartz watch you should have a variable voltage power supply and a meter capable of measuring microamps. Then the lubrication on these watch is really critical. Originally they felt that no lubrication was required because it's just step paying and there's no load and that didn't work. Then they went the lubrication but that can have issues I would go with quartz watch oil which is really really liked.

 

[HectorLooi]

But before going off to buy a replacement stepper motor or pcb, it would be best to follow protocol and use a quartz watch tester to check for a pulse and use the "line free" function to spin the gear train. Sometimes dried up lubricants can gum up a movement enough to stop it.

SG$ 35.16  38%OFF | QD-20 Watch Maintenance Tool Quartz Movement Tester Made in China Watch Movement Tester Can Measure the Battery
https://a.aliexpress.com/_mtjhhPU

[Kalanag]

7 hours ago, HectorLooi said:

But before going off to buy a replacement stepper motor or pcb, it would be best to follow protocol and use a quartz watch tester to check for a pulse and use the "line free" function to spin the gear train. Sometimes dried up lubricants can gum up a movement enough to stop it.

SG$ 35.16  38%OFF | QD-20 Watch Maintenance Tool Quartz Movement Tester Made in China Watch Movement Tester Can Measure the Battery
https://a.aliexpress.com/_mtjhhPU

Does this cheap tester offer the „line free“ function?

[JohnR725]

19 minutes ago, Kalanag said:

Does this cheap tester offer the „line free“ function?

if you look at the website that selling it seems to have all sorts of nifty features in fact way too many features for the price? It be really nice if somebody would do a review.

here is a video of an older version still looks really impressive for the price though. Although it still doesn't do or have a variable voltage power supply or any way to measure microamps things that I like to do when testing quartz watches

https://youtu.be/VBnZk8Ly8gk

it's amazing what you'll find on YouTube. This quite a few videos on the older style here is one showing the newer one and it almost seems just too good to be true.

https://youtu.be/j8958_MV8eI

 

 

[Kalanag]

1 hour ago, JohnR725 said:

…it's amazing what you'll find on YouTube. This quite a few videos on the older style here is one showing the newer one and it almost seems just too good to be true.

https://youtu.be/j8958_MV8eI

Thanks for the link!

It seems to me that the „line free“ function is realiced by a alternating magnetic field which is also used to demagnetice mechanical watches. For me it‘s a „brute force attack“ to the quartz movement for just testing the gear train. It is not suitable for testing the stepper with its electronic driver circuit.

Edit:

To prove my claim of „brute force“ I took a cheap quartz movement with just a seconds hand attached and put it on my demagnetizer

https://youtube.com/shorts/TlOY6hkFYgE?feature=share

Edited June 4, 2022 by Kalanag

[HectorLooi]

3 hours ago, Kalanag said:

Does this cheap tester offer the „line free“ function?

Yes it does. It also has a "timing error" function where it measures 12 pulses then gives the daily deviation error.

[Kalanag]

36 minutes ago, HectorLooi said:

Yes it does. It also has a "timing error" function where it measures 12 pulses then gives the daily deviation error.

Forgive me if I‘m not impressed to much about this tool. The „time error“ function is just as good (or bad) as the internal quartz time base and the „line free“ function can be performed by any basic demagneticers imho. Nevertheless price vs. function seems to be o.k..

[PastorChris]

Well I ended up finding a working watch that I bought for parts. It turned out it was indeed the stepper motor with the other components working fine. Not a big surprise but I sure like this watch!  
 

 

[Pheme]

Great divers watch version, but horrible bracelet. I’d replace it with a silicone divers strap.

I have the same movement in a gold pocket watch from 1978 (N8 on inside case back). It runs for a while, then the second hand stops or just vibrates. It will restart if you slam it against a tabletop. Probably also a defective stepper motor.

Did you have to solder in the replacement stepper?

[JohnR725]

4 hours ago, Pheme said:

It will restart if you slam it against a tabletop.

you usually don't hear the word slam associated with watch repair interesting technique.. Probably not recommended though best not to do that with mechanical watches.

 

4 hours ago, Pheme said:

Probably also a defective stepper motor.

hard to tell with your diagnostic method as to whether it's a stepping motor or not..  Sounds more like a watch in desperate need of servicing because the oils can go bad with time and that's a problem.

4 hours ago, Pheme said:

Did you have to solder in the replacement stepper?

somewhere up above you can download the PDF of the service manual I snipped out one of the images for you I circled the stepping motor. You have to disassemble the watch but the stepping motor comes out as a unit.. A very long time ago they were available for purchase but not anymore you to find another one that's functioning

[HectorLooi]

I came across a replacement motor from Cas-Ker recently but it's a little pricey to just buy and try.

https://www.jewelerssupplies.com/accutron-242-step-motor-20-510-900.005.11.html

 

I wrote about my adventures with a Bulova 242 last year. I just bought an untested 242 movement off eBay and am praying hard that it works.

You might find it useful.

Apparently, this twitching problem is quite common with the 242 stepper motor. I haven't really looked into the cause. 

[LittleWatchShop]

I am wearing the RR approved version (I believe same movement but different case).  I love the accuset feature.  A bit of a gimmick as viewed from 2023, but still clever for its time.

I have two of these watches.  Would have been able to help you, but you found a solution!!

Nice case!!

[JohnR725]

5 hours ago, HectorLooi said:

I came across a replacement motor from Cas-Ker recently but it's a little pricey to just buy and try.

nice find and if this is what it would take to get the watch to run isn't really that expensive. Of course if you have to add in a circuit board then it will get more expensive which is why testing is nice proper testing. To figure out what the problem may or may not be as opposed to jumping to conclusions. Which of course is the problem with electric watches you need a electric watch testing equipment amongst all the other stuff we have to have.

[LittleWatchShop]

2 minutes ago, JohnR725 said:

amongst all the other stuff we have to have.

It is never enough!!!

[JohnR725]

1 hour ago, LittleWatchShop said:

It is never enough!!!

it's why I try really hard not to look at eBay. Because there's always something that I'm sure I need. So this means now I exert a lot of energy to try to avoid any place that has the resemblance of wanting to take my money and sell me something.

[HectorLooi]

Just a quick update. The untested movement arrived on Friday. It was all in pieces, packed in a double envelope. I heaved a big sigh when I saw it as it didn't look good. But it only cost me $2.75 and $30 in postage. 

I cleaned up the motor and fitted it in my movement. Powered it up. Bigger sigh.  

It was only twitching. I swapped the circuit boards and prayed hard. But alas.... only twitching.

Then I did what @JohnR725 said he did years ago. I peeled off the transparent plastic sticker on the bottom of the motor, squirted in lighter fluid because I didn't have freon. Blasted it dry with compressed air, then fitted it in my movement again.

Miracle!  It works!

I left it running on my bench and will check on it tomorrow. It's already past 1am here in Singapore. 

Wish me luck, guys!