New Watch Rebuild – Stunning 70's Seiko Bullhead – Dual Register Chronograph – OSA Owned – Tons Of Pics

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thor447

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The watch was keeping excellent time (within 5 s/d) with excellent timegrapher traces showing that the escapement (balance/pallet fork/escape wheel) were working very smoothly without any hint of an issue. In all fairness the watch would've probably ran just fine like it was, and no one would ever notice anything, but the timegrapher's amplitude readout clearly showed that there was a fault somewhere stealing power from the watch.

The first thing I did was strip the movement down completely again, re-cleaned everything, and started the process of inspection, again. I found that the center wheel had a bit too much end shake (up and down free play). You need a little bit, but this watch had a bit too much. This was fixed by simply adjusting the depth of the jewel in the center wheel bridge, lessening the amount of available up/down travel that the center wheel has between the upper and lower jewels. Inspecting further I found a damaged lower barrel arbor jewel, where the inside of the lip has a very small chip in it. This will definitely steal power from the watch. When the watch came from the factory, it had a jewel in the lower barrel arbor port, but a steel bushing in the upper port as previously detailed.

As luck would have it when I purchased the barrel arbor jewel kit for the watch it came with both an upper and lower jewel. I only ordered the upper jewel because that's all I should have needed, but when it arrived it had an upper and lower jewel together. This was really great news because I had exactly what I need to make this repair without having to order anything else.

Here's a picture of that damaged jewel. It is very small, and the chip is even smaller, so it was difficult to get a clear pic of it, but I think you can see it well enough. In the 11 o'clock position.

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I can see why I missed it in my initial inspection. I had to remove the 0.5 Barlow lens off of my microscope, effectively doubling it's magnification, and then play with the light source to be able to view this flaw in the old jewel. Thankfully having the part on hand, I removed the old jewel and installed the new one using the same process as previously described when upgrading the other barrel arbor jewel.

After getting this repair completed, I took all of the parts for the watch and fully cleaned them (yet again) and assembled/lubricated everything......yet again.

That fixed the low amplitude issue, and now this thing was running beautifully.

The dial and hands were then installed.

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After testing that the resets all worked correctly, I put a full wind in the watch and let it run in for nearly 48 hours with the chronograph running the entire time. During that time I reassembled the case and installed the new crystal.

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thor447

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After it's run in period I did just a tiny amount of final regulation. Afterwards I installed it into the case.

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Here is the final timegrapher readouts. It now has an excellent amplitude for this movement, with clean trace lines, etc. It's running very well.

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With the watch assembled and running great I installed the NOS bracelet. Here's a photo of the old one next to the new one.

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This watch is a real stunner. It was a real pleasure to work on it, even if it did cause me to pull my hair out a time or two when trying to trace down where the power loss was coming from. Thanks again to the owner for trusting me with it.

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If it wasn't evident by the length and detail of this thread, I am a big vintage Seiko nut. I especially love these 70's era chronographs. I have one really special first year 'Proof' model UFO I've fully rebuilt for myself, and three others on my bench waiting on future repairs & rebuilds, which will one day go into my watch box.

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Technically speaking I only had 3 of these watches a short time ago, but working on this Bullhead really pushed me over the edge on getting one for myself. So while I was rebuilding this one for one of our longtime fellow OSA members, I ordered a really cool old brown/tan Bullhead for myself. It has some mechanical issues. The hammer spring is broken, and the bushing for the minute recording wheel is just flat out missing from the chronograph bridge. Needless to say I got this one for a good deal. All of it is fixable though, and the missing bushing will be upgraded to a jewel. This one is not in the same condition as the one in this thread, so I'm not worried too much about originality. It is going to get the full treatment and will look like it did the day it came out of the factory when all is said and done. I don't know when I'm going to start on it, but it'll probably be sooner rather than later since now I don't have that gorgeous blue/black Bullhead on my bench staring back at me!

Well, this is far and away the longest watch rebuild post I've ever done. I have absolutely no desire to go back and read through it to check for spelling and grammar, so any mistakes on my part in that area will just have to stay that way! My fingers hurt, and I'm about to go enjoy a glass of iced tea and some Star Trek. A good evening to you all!
 
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Perplexed

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If this keeps up, we’ll need to rename the forum to “Oklahoma Shooters and Horological Association” (OSHA) ;)

Fantastic write-up and stunning restoration! My hat is off to you once again for your patience, perseverance, and dedication to such a painstaking and delicate endeavor, Adam.
 

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