mastrmindalliance Posted August 12, 2011 Report Share Posted August 12, 2011 Hi, hoping someone might be able to help with a little bit of knowledge. My 328 with a7750 has recently been back to china. After getting it back I thought I could hear the rotor catching on the movement. I took the caseback off to check the screw. Tight. No problem there. There was a problem though - two of the blued plate screws were loose inside case. These two marked with green arrows: After some research finding where they belong - I went to replace them. As I was screwing the second one in, the movement made a noise and motion that gave me a bit of a startle. A quick two second hi-speed "whir" and a little vibration. I didn't think it was the watch at first. I thought I'd imagined it. So I put the rotor back on and spun it with toothpick to check it spun even, as I always do. Uhoh - maybe I wasn't tripping before - it now has clicky resistance in both directions. A bit more research around the web uncovered similar symptoms with bad reversing wheels allowing the mainspring to unwind. Two unusual things though - it doesn't turn the rotor when I wind the crown - this seemed to a symptom of all the bad reversing wheels I read about. The other strange thing, it's been ticking away happily for about an hour now since it unwound (if thats what it did do). I figure if it unwound it would have no PR left...? So two questions, a statement and apology... Q:Does it sound like the mainspring caused by a bad reversing wheel to you? Q: Could I fix this myself? My skill level is such that I can successfully fix things around the keyless works and little beyond in a 2836 and 2824. I know this is a completely different beast. Statement: this rep is the crappiest build quality of any I have bought. The steel is so soft you have to place it on velvet pillow like the bloody crown jewels so it wont ding. Seriously, if you scratch your [censored] with this thing on, the bracelet will need refinishing and parts have been falling off it, inside and out like a leprotic zombie since the day I got it. it sure is pretty though Apology: sorry for the long post Any help appreciated. Link to comment Share on other sites More sharing options...
FxrAndy Posted August 12, 2011 Report Share Posted August 12, 2011 Check that the spring indicated by my black arrow is sat on the botton gear (ratchet wheel) of the reversing wheel and it has not slipped under it and pushed the reversing wheel out of the jewels the power of the main spring may have been held soley on that ratchet if the other spring (long bar at 11 on you picture) on the main wheel was not engaging propperly, the sownd you heard would have been the main unwinding as the spring came off the ratchet wheel of the reversing wheel Link to comment Share on other sites More sharing options...
mastrmindalliance Posted August 12, 2011 Author Report Share Posted August 12, 2011 Thanks Andy, and I think you're onto it. I think can actually see that little spring clicking on the top wheel through the little hole. Many posts here have put the fear into me about tinkering on a7750s but I'll give it a go. As pretty as the watch is, one thing's for sure, if i break it i'll just part it. This isnt worthy of sending to The Zigmeister. Hope they come out with new version from different maker. Link to comment Share on other sites More sharing options...
Rolexman Posted August 12, 2011 Report Share Posted August 12, 2011 + 1 what Andy said. Try the little spring. But it highly unlikely that the little spring caused the main spring to unwind. Maybe 1/2 a turn but not completely as the click holds the main spring in place (large arm at 11 o'clock). Are you sure the reversing and the reduction wheel are properly seated in the jewels? Could be the 'clicky resistance' comes from the gear teeth not properly engaging. Let us know how it goes. Link to comment Share on other sites More sharing options...
mastrmindalliance Posted August 12, 2011 Author Report Share Posted August 12, 2011 Thanks for the replies guys But it highly unlikely that the little spring caused the main spring to unwind. Maybe 1/2 a turn but not completely as the click holds the main spring in place (large arm at 11 o'clock). that would make sense as it ticked along for about 8 hours after that. Rolexman, everything else appears in order with the naked eye and to someone with no 7750 experience at all. For those who know about 7750s, a quick question before i pull it down... is there anything particularly tricky or unforseen under that plate? Like, this isn't one of those parts that bits fly out from the movement once removed is it? Any general tips or cautionary tales for a first time 7750 tinkering on this side of the movement? Should i be popping dial and hands for this? once again, any insight is much appreciated. Link to comment Share on other sites More sharing options...
Rolexman Posted August 12, 2011 Report Share Posted August 12, 2011 For those who know about 7750s, a quick question before i pull it down... is there anything particularly tricky or unforseen under that plate? Like, this isn't one of those parts that bits fly out from the movement once removed is it? Yes, this bridge is the trickiest bridge of the entire movement. A lot of things have to be taken in to account. First of all the hammer spring needs to be removed. Otherwise all the parts will fly across the room. Besides that you probably have to reposition the tilting pinion, hammer and clutch before placing the bridge back on. If you've never done that before and don't have the right tools, tweezers etc. you will have a hard time getting it back together. Go for it if you have nothing to loose. Otherwise have an watchmaker look at it. Link to comment Share on other sites More sharing options...
mastrmindalliance Posted August 12, 2011 Author Report Share Posted August 12, 2011 Darn it, looks like i've found the problem. The spring mentioned above (the "stop click" spring or part 1428 on the 7750) is bent beyond a right angle). i will try straightening it, but i know it will require a new part. edit; just before i do, i better check that it the a7750 isnt supposed to be bent like this: it's supposed to be perfectly straight isn't it? Link to comment Share on other sites More sharing options...
Rolexman Posted August 12, 2011 Report Share Posted August 12, 2011 The spring is usually a bit bend. Not as much as on your pic though. Link to comment Share on other sites More sharing options...
mastrmindalliance Posted August 12, 2011 Author Report Share Posted August 12, 2011 Yahoo! Fixed and back on the wrist! Thanks for your help FixerAndy and Rolexman. It's always nice to have to have a win the first time you tinker with a new movement and i couldnt have done it without both your insights. I do doubt the longevity though as the spring had be straightened. So its probably 'sprung' now. I'll endeavor to get a replacement and offshore's moebius oil and go back in at some stage. I'll be adding checking bridge screw tightness to my list of todos when i receive a rep from here on in. Thanks once again guys. Edit: thanks again Rolexman, we posted at the same time - i did leave it a little bent Link to comment Share on other sites More sharing options...
Rolexman Posted August 13, 2011 Report Share Posted August 13, 2011 Great job!!! Knew you could do it Link to comment Share on other sites More sharing options...
FxrAndy Posted August 13, 2011 Report Share Posted August 13, 2011 Good news Link to comment Share on other sites More sharing options...
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