I have just finished putting back together a f300hz which had the main issue of a dead transistor assembly. I replace the part from a donor Tissot. Having confirmed the watch was running, I proceeded to service it and the put it back together. I focussed on the movement and was very careful not to interfere with the two levers that drive the movement from the tuning fork. (Not sure what these are called). The watch seemed fine although I don’t have a method of timing the watch other than visually. ( am pretty sure my timegrapher is not going to cut it!)

I timed the watch for an hour and it seems to gain about a minute+. I left if for about 13 hours and it is running around 15 minutes fast. I then decided to give it a stopwatch test, as the variance appeared to be large enough to detect it this way. Sure enough, testing via a stopwatch with a lap timer showed a significant gain with a 6 minute test completing in 5 minutes no 51 seconds. (See attached images, which included lap times by eye (the 5th one was definitely slow due to me losing concentration), allowing for reaction times, it looks pretty consistent.

My understanding of this movement is that the timing adjustment is via two dials at the foot of the using fork but, from what I have read, each increment is only a second, which is not going to be anything like enough and, regardless, this variance suggests something seriously wrong.



I checked the battery and it seems to be the correct one from what I have read is correct, a Renata 344. One more thing to note is that I replaced both electronic units from the donor.



So I am now a bit stuck. Any advice or pointers to where I can find additional information would be very much appreciated.

 

The's a adjusting screw for the corrector plate on the side of the oscillator (top) plate. This is where the non-moving pawl is fixed to. You can adjust that so it's running correct. The problem here is that the pawl isn't having the correct presure agains the index wheel, so it it will jump some teeth or double index. When you turn the screw, you will have several points where the speed is faster than normal. Just a small adjustment should be enough.
Idealy, you should check the whole voltage range of the battery, 1.05 V to 1.65 V to make sure is doesn't double index when the battery is fresh or stop before the battery is depleted.
Take a look at the service manual: https://watchmaker.hu/wp-content/uploads/2017/12/ESA Cal.209162 Repair Manual.pdf
You can use an old battery and a fresh battery in place of a variable power supply, just measure the voltage to make sure it's not below 1 V.
You'll need good light and a loupe with strong mangnification so you can observe the index wheel when you adjust. If this doesn't work, you need to re-adjust both pawls using the gauge that's on the top plate in place of the index wheel. There's a _very_ high risk of messing up the pawls so don't do this unless you have a microscope and very steady hands!

 

A couple additional links that you might find helpful:
1. ESA 9162 Manual (similar to above, but better quality photos): https://myretrowatches.co.uk/wp-content/uploads/2020/09/ESA_9162.pdf
2. Phasing Accutrons for Silver Oxide Cells (see the F300 related comments): http://knob.planet.ee/kirjandus/manuals/bulova/accphs.pdf

 

Surely a much better copy of the service manual. When it comes to phasing or adjusting indexing, there's no point going above 1.65 V. A modern silver oxide battery will never have higher voltage. I usually adjust from 1.65 V down to 0.9 V to make sure it runs well when the battery is empty.

 

Thanks for the detailed reply!
I looked at both pawls referencing them against the technical guide images and they appear to be correct. I don't see any slipping and they seem to be flat (i.e. the pressure is not so high that they are bowing) I will take another look though, based on your comments. I do have a microscope and will be using that, rather than a loupe (which I tend to avoid, unless I am using a jeweling tool or staking set). The battery is new but it might be worth checking as it could be a problem. My issue here would be that I would expect low battery voltage to result in time loss rather than gain.
I've looked at the service guide and a couple of things are worrying. One of the statements in the manual is that time variances over 8 seconds per day are not covered and the watch should be sent back to Omega. I am wondering if you have an opinion on this statement (the bit about time adjustment limitations, not the bit about returning the watch to Omega!) The other problem is that there are access points to test voltage and resistance of the circuit but there are no adjustments. I am concerned that the replacement circuit I got from the Tissot has a different transistor to the old one and the gate is switching faster as a result.

 

Thanks for this. I already have a copy of the guide but I'll check to see if the version you reference is a better copy. The second link looks interesting I will definitely check that out, thanks!

 

I just checked and that is a better copy than the one I have XD. I'm interested in your comments about phasing and adjusting. I need to have a good read of that link as I don't currently understand your reply

 

This video was invaluable for me to service my 214 Accutron. I use a microscope to aid in properly adjusting the pawls. Those are tiny and the adjustment critical in a properly functioning Accutron.

 

It's not how it's working. The tuning fork will always resonate at the same frequency, no matter the battery voltage. This is given by the length of the tuning fork. You can adjust this slighly with the weights on the end. If the pawls have the correct pressure, the index wheel will advance one tooth pr. oscillation. If the pressure is not correct, it will sometime advance two (or more?) teeth and then it goes too fast. If there's dirt on the index wheel teeth, it may jump a tooth also.
When the battery voltage gets lower, the amplitude of the oscillation will be lower and at some point, it's too low to advance the index wheel and it stops.

The coils are just mainaining the oscillation of the tuning fork. The transistor side has two coils where one is connected the base of the transistor. The magnet on the tuning fork will generate a voltage over this coil and open the transistor. This in turn will energize the other coils and give the tuning fork a gentle push to maintain the oscillation. If it oscillates (or hums), the coils are just fine so leave those alone and look at the index wheel and/or the pawls.
If you look at the index wheel in the microscope and turn the screw, you will see what I mean with the speed changes.

 

To add to @ketiljo excellent response.
The motion of the tuning fork causes the index to move back and forth (double-headed arrow on the diagram below). When the voltage increases, the amplitude of the tuning fork increases. This might cause the index jewel to land further away than the edge of a tooth and end up on a tooth too far away. This causes the watch to run fast.

 

You need to know if the slow rate is caused by the tuning fork vibrating at lower than 300Hz, or by slipping of the index teeth. I would adjust the index jewels only if I am sure the fork is vibrating at right frequency. Also, the fork is magnetic, and if a small metal piece is stuck to the fork, the frequency will be off.