How to open Sony Digimatic 8fc-59w gearbox

[Maarten Baijs]

My dad and me are trying to restore a Sony Digimatic 8fc-59w.

The clock isn't working; the motor (Copal II) is spinning, but the gearbox's output shaft cannot rotate the clock mechanism. The clock mechanism seems to be working and can be rotated by hand just fine. We noticed that when the gearbox's output shaft receives a little bit of resistance, it makes a clicking noise and slips. We think a gear in the gearbox is worn. To know for sure, we need to open the gearbox.

We are struggling with how to go about doing this. The output shaft has an oddly shaped "gear" at the end and the shaft at the end has a metal "stopper" keeping us from pulling the “gear” off. Does anyone have some pointers on how to open the gearbox?

greetings,

Maarten and Martin

[Johan de Jong]

Hi Maarten and Martin,

I have a Sony 8fc-59w that is missing the motor so that is not of any help to you (the other way around it is for me, because now at least I now what kind of motor and gear/wheel I need to look for ).

But I do have another Sony with a motor that looks similar but has another odd wheel on the outgoing shaft. The shaft has a flattened end that looks very similar to the shaft in your picture. On my motor I could just pull the plastic gear off. There was no "stopper".

[Maarten Baijs]

Thanks a lot for your input, we managed to open it! As you can see in the picture, one of the gears is worn. We hope we will be able to find a replacement.

Do you know if the gearbox should be greased? There is some black powder inside, could this be very old lubricant?

[Johan de Jong]

Great you got it open!

To further open up the gearbox this post may be helpful: https://www.flipclockfans.com/forum/...box-for-repair
And to replace the gear possibly this post: https://www.flipclockfans.com/forum/...-a-copal-motor

But in your case it is a different gear that is broken. In the photo it looks like only part of the small gear has worn and the rest is still good. So it might be worth a try to cut of the small gear, turn it around and glue it back to the large gear so that the good part is used.

If that fails you will need to find a replacement. You could get one from a donor clock if you have one or buy a new one from kkpmo.com. If you can determine the number of teeth, diameter and thickness you can look it up there. Most likely the gear module is 0.25 but please double check that all the data matches with the broken gear.

That black powder could be the remains of dried out lubricant indeed. The gears need only a light lubrication. Any light oil will do.

[Maarten Baijs]

Great you got it open!

But in your case it is a different gear that is broken. In the photo it looks like only part of the small gear has worn and the rest is still good. So it might be worth a try to cut of the small gear, turn it around and glue it back to the large gear so that the good part is used.

Hi Johan, do you have a suggestion on which glue I can use for glueing the gears together? I tried superglue, but it doesn't seem to bond very well.

[Johan de Jong]

POM is indeed very difficult to bond (https://en.wikipedia.org/wiki/Polyoxymethylene#Bonding). I used superglue or superglue gel and often needed multiple attempts before I could bond them successfully. I think part of that success comes from that after each attempt I scrape of the remaining glue and by doing so roughen up the surface. So I also tried a very fine sandpaper to see if that helps. I don't have enough experience with it to conclude if it really helps, but for certain it did not harm.

[Maarten Baijs]

I'm assuming you are also from the Netherlands? Which brand of glue are you using?

[Johan de Jong]

I live indeed in the Netherlands.
And true to our national habits I just use the cheapest glue I can find .
Both available at Action: Pattex instant glue and Bison super glue gel.