This is a sad looking Tissot Seastar from 1968. I purchased this watch back in January of this year as it looked like it had some potential for restoration and I could see the previous owner was clearly a “watch guy” as he kept on a Rolex bracelet; I haven’t decided what will become of the Jubilee bracelet yet but for the price, it was a nice toss in.
The watch ran when I received it but it was hard to gauge how well since the crown was missing. I discovered the winding stem was still logged inside the tube though and a bit of digging around in my parts bin uncovered a crown which would fit for testing.
Eager to engage in a more straightforward mechanical watch service after trying my hand at some Accutrons and pin-pallet movements, I popped the caseback off to see what was inside. What a found was a nicely finished Tissot 796 automatic movement which appeared a little grimy but in good shape.
Before extracting the movement from the case, I removed the automatic winding rotor. Since the the rotor spins easily on it’s post (for the purpose of winding the mainspring) it’s usually best to remove the rotor first thing as handing the movement with the rotor attached is a bit like holding onto a wet bar of soap.
To this point I’ve only done one full service (breakdown, clean, reassembly) on an automatic movement, thus I’m careful to take many pictures during disassembly to ensure I get each piece back in its proper place!
One thing to look for when servicing an automatic movement is the amount of wear visible on the rotor edge and inside the caseback. The rotor should spin freely without contacting the caseback or any of the bridges beneath it. A worn bearing will result in excessive play and scuff marks on the caseback or rotor itself. This rotor had a little bit of wear visible on the underside suggesting it may have been coming in contact with the automatic bridge.
Before removing the automatic works and gear train, the calendar works needed to be broken down. I flipped the movement over and removed the dial to reveal the day and date disks.
The day disk lifted away easily to review the calendar bridge.
Disassembly of the calendar works of any watch can be a gut wrenching affair. There is usually no less than two springs which are waiting anxiously for the novice watchmaker to liberate them from their prison. They’ll often take flight, never to be seen again. In this instance I was very careful (and also a bit lucky), the calendar works came away without incident.
I then moved back to the topside of the movement and disassembled the automatic works.
With the automatic works removed, the movement became a recognizable standard Swiss mechanical with the crown and winding wheels on top of the barrel bridge and the gear train beneath.
There were a few surprises be found beneath the barrel bridge however- the first being oil- lots of oil!
Before disassembly I had noted that it was impossible to wind the watch using the crown as the watch was stuck in the setting position. Removing the barrel bridge revealed copious amounts of viscous oil pooled around the setting mechanism. I guess the previous owner had issues setting or winding the watch and blasted oil inside through the stem tube. Perhaps he figured after the crown fell off it was the best form of water protection…
The second thing of interest was how Tissot designed the sweep second mechanism as both the forth wheel and sweep second wheel are driven off the escape wheel. The third wheel and second wheel (center wheel) are located beneath a secondary bridge. I’ve not seen a sweep second watch constructed this way before but I like the design.
With the gear train disassembled it was time to finish up with the keyless works. Here is where the only real problem was discovered as the setting lever was badly mangled. This explains why I couldn’t wind the watch.
The disarticulated movement went off to the cleaning machine and I proceeded to break down the watch case.
The Tissot PR 516 is an interesting beast primarily because of it’s case. Nobody is quite sure why Tissot named the watch 516 but the PR stands for Particularly Rugged or Particularly Robust. The case is milled out of a block of stainless steel and is designed to take a beating. The acrylic crystal is fitted with a tension ring and the caseback is threaded to insure the watertightness expected in a diver’s watch.
I particularly like the crystal design for this model though. The index markers are attached to the tension ring within the crystal. This creates an additional level of depth as the hands float below the index markers and above the sunburst finished dial. Unfortunately replacement crystals with index markers are not available.
I ran the case and caseback through the ultrasonic cleaner and set to work on the crystal with the cordless Dremel and a bit of acrylic polish. The brushed finish of the case was cleaned up with a Scotch-Brite and the sides were polished back to a mirror finish.
Reassembly was fairly uneventful except for the mainspring which is wound the opposite direction of most Swiss mainsprings. The solution to this problem is just to drop the wound mainspring into a washer which has an inside diameter equal to or slightly smaller than the mainspring barrel, then flip the washer over to drop the mainspring into the barrel. The result will be a mainspring wound the proper direction for the barrel arbor.
Before assembling the setting mechanism, I fixed the damage to the setting lever using a flat stake in my K&D staking kit and a few taps from the jeweler’s hammer. The result was a correctly working setting mechanism.
A proper sized Tissot crown was sourced from Cousins and I added a new stem to the order just in case.
Everything had gone swimmingly right up to the point that I tested the calendar setting. For reasons that I’m still trying to understand, the calendar works had seized up resulting in a tooth being knocked off the hour wheel when I turned the hands over midnight. This caused much consternation as the hour wheel for a 796 movement is just about impossible to source. Luckily I was bailed out by OldSwissWatches who had the part in stock. I had to shelve the job for a few weeks while I waited on delivery.
The end result was a beautifully restored Seastar Automatic.
The popularity of this timepiece has proved to be lasting as Tissot has recently begun production of the PR 516 once again. The current rendition doesn’t have the floating dial which I think is a nice touch that gives a bit of depth to the piece. This particular one keeps impeccable time and has aged exceptionally well. I couldn’t be happier with the result.