Luch 3055 A Russian oddity...

[Alastair]

This is an oddball machine, an Electric style balance-wheel watch--With a Quartz crystal and the associated drive circuit.

This one was dead--no run. Balance staff intact, moving freely.

The way it works-A chip based crystal-oscillator derives a  square-wave that feeds a pair of transistors that drives the coil set--At the right time. One transistor is switched by the other depending on what position the balance is-Referenced by a feedback winding, which then turns on to supply the coil set with the drive pulse....

I'm not sure the actual frequency of the quartz crystal.... Some of these early quartz watches had weird crystal frequencies

This one had good coils but still no life with new cell. Voltages seemed as they should be. I used an oscilloscope to check the oscillator--not much use, I think it was damping out the quartz too much. What it did show was I had a nice strong square wave signal at around a volt p-p. 

This dissappeared under some nasty white paint on the circuit board, into which also lead the tracks from the coils. Nothing to loose--I removed the circuit board--Which involves removing many small screws, then dissolved the white crud with some acetone. I used a fine artists paintbrush to apply the acetone. It dissolved pretty easily and showed two tiny transistors mounted on brass tags soldered to board with two very fine gold wires coming from each. One had come away from the brass tag--It had cleaved along the silicon itself!  I can only think it had been damaged by some external force.

I determined that the type was an NPN transistor, so removed the two and using a little logic and a schematic I found on the Web, I installed two BC848  SOT23 transistors. (If I ever need to do another of these--I would use a smaller package than a SOT23 as soldering these in was a real pain!

It worked! The watch ran. It now has a mechanical issue. The 'escapement doesnt seem to work correctly. pallets on one bank-pin from centre line, the wheel moves one tooth going to other bank pin, again it advances a tooth--But when pallets move back, the wheel does also. (doesnt always, but often) Ive cleaned the movement,--but TBH I dont 'Do' Mechanical watches--Tuning forks are my thing... I got this thing because of its oddity--A quartz osc controlling a balance--Outrageous-- gotta get me one of those! hence the trouble....

I'm guessing either the wheel or the pallets, but how to check? I cant find any diagrams that show this type of escapement--so have no idea whats the problem. Any ideas--or even a service instruction (yeah right LOL)

 

[HectorLooi]

Good to have you back. You seemed to have gone MIA for a couple of years.

I haven't worked on a Luch before but I've done quite a few Timex quartz. 

It could be just dried lubricants on the mechanical side. If you remove the balance wheel and move the pallet fork manually, does the escape wheel move in one direction only of does it slide back sometimes?

On some of the Timexes, there is a small permanent magnet on the bottom plate that pulls the pallet fork and holds it in the fully banked position until the impulse jewel returns and swings it to the other side. The magnet gives it the "snap" action that is similar to mechanical watches. I've come across a few where the magnet is so weak that there isn't any snap action and the wheel just swings back and forth, like you described.

I suspect that some watchmaker must have run the movement through a demagnetizer previously. I did manage to revive one by rubbing a small, powerful neodymium magnet on the magnet to remagnetize it.

[everyonesdesign]

These watches are peculiar indeed, but I've heard they're very finicky when it comes to adjustments.

Here's some good articles (in Russian) containing the electric circuit diagram and the mechanical parts diagram for Luch 3045/3055 (I'm not an expert, not sure how big the differences are between those movements; layouts look differently, but I think the principal schema is similar):

• http://ussr-watch.com/luch-3045-mezhdu-mehanikoy-i-kvartsem/
• https://chronometrica.ru/luch-3055-movement/

Let me know if you need help with translations.

Apparently, Luch were not the first ones to implement such an oddity, there's Junghans Electronic 600 movement based on the same principle, which was probably copied by the Soviet engineers.

I wasn't able to find a catalogue picture of Luch 3055 watch, but here'a photo from a 1974 catalogue, proudly advertising a watch with Luch 3045 movement (± 20 seconds per day, battery lasting 12 months).

TIL: it seems that Hamilton was the first manufacturer employing this principle of passing energy to the balance? https://www.safonagastrocrono.club/slava-114-chn-a-brief-history-of-electric-watches-in-the-soviet-union/ 

I'll also try to look up any mentions of this type of movements in my watch repair books, I think I might have seen it mentioned somewhere.

Also might be useful: this article (in Spanish) contains some nice schemas showing the anatomy of Luch 3055: https://www.safonagastrocrono.club/luch-3055/

> I'm not sure the actual frequency of the quartz crystal.... Some of these early quartz watches had weird crystal frequencies

According to some sources I found on Google quartz resonator "РВЧ-72" used in Luch 3055 has a frequency of 32768 Hz 

[Alastair]

Ah--wow, thanks! thats all great info!

As I recall, there was a strange V shaped thing attached to the pallets underside (that look like ordinary Swiss Lever style)--Maybe there is a magnetic thing there. Will pull the thing down again and see....

[Alastair]

Well, I did pull this apart again and yes it did have a tiny magnet under the pallets. This turned out to be fine and does give it a significant 'draw' The 'run to banking' seems the same both sides for the pallets.

During reassembly however I managed to bugger up the coil, whilst trying to slide those daft shims under it!

The fault of the escape wheel moving backwards remains however when even the slightest load is presented to the train, (which is completely free otherwise) The centre seconds brake-spring cannot be fitted or the escapement 'balks' The ratchet above the escapement doesnt seem to do much either, apart from stop the movement all together, when adjusted to just touch the ratchet wheel. All academic at the moment till I find a new coil for this thing...

Any good suppliers of Soviet equipment and parts around?

[everyonesdesign]

Hm, unfortunately, no good suggestions from me apart from sourcing a donor from eBay and hoping that the parts you need are working. I think it'll be hard to find parts for this particular movement separately since it was manufactured for only a relatively short time span.

Edited August 4, 2023 by everyonesdesign
typo

[Alastair]

Allegedly, it was made for 7 years, many thousands were made as a cheaper alternative to --proper quartz...

Maybe I'll get lucky!

[HectorLooi]

There are a few non runners on eBay at the moment. 

So tempting.... but I'm still looking for a Seiko Elnix or Citizen Cosmotron.