Bulova 17AH regulation

[Guy Williams]

I need some helpful hints adjusting a Bulova 17AH. I have the watch beat error down to 0.5 msec but I need to get the face-up and stem-up rates much closer. Face-up is running about -5 s/d stem-up is running +33 s/d. The regulator pins are tightly closed but not touching. What can I do to get the rates closer? The regulator adjustment is centered and the watch runs nice straight plots.

I am not familiar with what the normal adjustment positions are for a good PW. I did have a Hamilton 992B that was adjusted 8 positions. I assume this means 5 positions and three temps. Since the Bulova was Swiss made it is marked 'unadjusted.'

Thank you for looking and I hope to hear you all.

Guy

 

[sderek]

Have you demagnetized it? Checked that the hairspring is perfectly centered between the regulator pins? This is best done with no power applied to the train.
You may find you'll have to replace the balance staff and/or balance jewels to get something better than what you have. As is it, you're probably got it running as accurately as, or perhaps even better than when it left the factory.

 

[Guy Williams]

Thanks! I am never one to do more than necessary. The watch is demagnetized, this if the first operation at my work station. I will make the unwound check you suggest. I got enough hours in this gem already. I am ready to call it good.
Guy

 

[doug sinclair]

Was the balance wheel checked for poise? Maybe a balance pivot a bit bent? Have you cleaned it?

 

[sderek]

Have you demagnetized it? Checked that the hairspring is perfectly centered between the regulator pins? This is best done with no power applied to the train.
You may find you'll have to replace the balance staff and/or balance jewels to get something better than what you have. As is it, you're probably got it running as accurately as, or perhaps even better than when it left the factory.

Doug brought up some good points. I gave my advice assuming you're already serviced the watch and checked the poise. Does it keep time to about +33 seconds in any pendant position (stem up, stem down, stem left, and stem right)?

 

[Jim Haney]

Guy,
I moved your question to the Watch Repair forum for better exposure. It is also a Swiss watch so it could have been listed in the European Forum for general discussion.
Thanks.

 

[psfred]

There are three things that come to mind here:

Poise (as noted -- if the balance is heavy on one side, Pendant Up can be very slow or very fast, depending on where the balance is heavy). If this is the case, the pendant right/pendant left positions will show wide variation AND the beat will be off in at least one position as the balance won't be swinging equally in both directions due to the heavy spot.

Hairspring location between the pins -- if the hairspring droops in the pendant up positions, it may not spend equal time on the pins. This is difficult to see, but if it "flys" in one direction while resting on the opposite pin in the other, the watch will run slow, and if it stays on on pin all the time pendant up, it will run fast. The distance between the pins makes a difference here -- closer = faster, farther = slower.

Excessive friction in the pendant up position in the balance jewels. Check for a chip or crack in one hole jewel, or grunge. The balance swing will also be much less if this is the case, obvious to the eye and also on the timing machine.

I'm sure there are other things (a pallet problem -- might check the escapment setup) or a locking problem that has much more effect vertical than DU. a loose dial causing drag in the pendant up position, etc, but the first three are what I would check first.

Since it's an unadjusted watch, it may have always been that far out, in which case you must make sure it stays vertical all the time to keep good time. There's a reason watch stands were invented (and there was a hook above each berth on the Orient Express in a velvet padded niche to hang your watch at night!).

Peter

 

[Guy Williams]

Hi Doug,

Good to hear form you. The watch is clean and demagnetized. Everyone talks about poise so I guess I will get THE tool. I have balance forceps but they are not sensitive enough.
I like the Orient Express hanging peg remark. Could be I have it as good as it gets. The watch has been running over 24 hours and still shows 160 degrees amplitude (started at 275'ish) and the isochronism is about 12 sec so far. I will check the at-rest hair spring position in the regulating pins when it runs down completely; it has a fresh spring.

Best,
Guy

 

[doug sinclair]

I didn't ask if it was "clean", I asked if you cleaned it. I often find that some folks call a watch clean if they don't see dirt when they look at the movement. I mean no varnish on the jewels, and all fresh, appropriate lubricants. My late father had a truing caliper to which he soldered about a 1/2" section of small, round file. He often told me that he could poise a wheel as well by putting the wheel into the truing caliper loose, and rubbing the file with the heel of his tweezer. If there is a heavy side, that will find it!

 

[Guy Williams]

I did clean the watch. Most watches I work on haven't seen service for many years. Any watch I receive is inspected under high magnification for just the sort of problems you discuss. I lubed the watch with four modern lubricants. I have read about the method your father used and it depends on the author as to efficacy. My guess is you go with what you have. I will try your dad's method and thank you for the reminder.
This watch was in pretty rough shape when I received and I happy to have gotten as far as I have. There is a question raised in this thread about the factory spec for the movement.
I work on modern watches too and where I can find specifications and I can easily meet or exceed them. My happiest times are working the occasional chronometer or top grade movement. There is not much to do but clean, lube and touch up the timing. These instruments are within a second or two in all positions.

 

[sderek]

Hi Doug, Good to hear form you. The watch is clean and demagnetized. Everyone talks about poise so I guess I will get THE tool. I have balance forceps but they are not sensitive enough. I like the Orient Express hanging peg remark. Could be I have it as good as it gets. The watch has been running over 24 hours and still shows 160 degrees amplitude (started at 275'ish) and the isochronism is about 12 sec so far. I will check the at-rest hair spring position in the regulating pins when it runs down completely; it has a fresh spring. Best, Guy

Before you take it apart to check the poise, it might be wise to just check the rate in all the pendant positions (crown up, crown down, crown left, and crown right). If the rate is very close in all positions, you can be assured it is poised. That's if you decide you need to take the effort.

 

[Guy Williams]

I have some measurements for you: PU -55, PD -126, PR -119, PL -119, FU -111, FD -124. At this time the pins are very lose on the hairspring. I will make the effort it looks like a poise problem. Again the traces, amplitudes and beat error look good.
If you sense there may be another problem please let me know.
Thank you.
Guy

 

[psfred]

I'm interested in what you find, as I have a watch that does almost exactly the same thing -- 60 sec/day or more difference between DU/DD and PU. Runs fast pendant up, too!

In my case, I'm going to be doing some work on the regulator pins eventually, they are not straight (someone bent on at some point to move them closer together, so there is a huge difference in contact time depending on where the hairspring is located).

I had decided that I still had a hairspring problem -- it got distorted as I worked on the watch and wasn't exactly right to start with -- but if you do actually have a poise problem I'll have to see what I can do with mine!

I assume you have checked the hairspring and it expands and contracts properly, not to one side, as that will have the effect of putting the balance out of poise in any position that enhances the lopsided expansion. If the hairspring goes off center, the balance will be out of poise from the weight of the hairspring sagging!

Peter

 

[sderek]

I have some measurements for you: PU -55, PD -126, PR -119, PL -119, FU -111, FD -124. At this time the pins are very lose on the hairspring. I will make the effort it looks like a poise problem. Again the traces, amplitudes and beat error look good.
If you sense there may be another problem please let me know.
Thank you.
Guy

Were these measurements taken with a full wind applied to the mainspring?

 

[Guy Williams]

Hi Peter,
I have put this project off until the weekend. I did work on the hairspring to get it centered, breathing correctly and centered between the regulator pins. I will strip the balance wheel an check poise to see where I am. This will be the first I have aggressively gone after this type of problem. The pros do a poise check as a matter course. As I said in an earlier post the import marking is 'unadjusted' and I am beginning to believe it. The watch has three dates scratched inside the back so who knows what went on?
I will post my conclusions.

Best, Guy
Guy