Need advice on fixing a stuck shutterspeed/asa dial...

My Canon F1 (old model F1n) has been sitting around doing nothing for a couple of years, and it is time to use a bit.... However....

Before I load film I go through the camera functions to make sure everything is ok, everything checks out except the slow shutter speeds and the self timer are a little slow and hesitant (common with old cameras in disuse). A few minutes of exercise and everything is back in shape.

The next day right before I go to use the camera I find a problem, something is now wrong with the ASA/shutter speed selector!

I can no longer select below 100 on the ASA dial and I can not turn the shutter speed dial at all...

Further inspection reveals that as I increase the asa up to 3200 I am able to move the shutterspeed dial, but not past 15!

Anyone have any ideas as to what is causing this?

really have no idea but THIS may help?

Thanks.... I guess maybe it is time to dig into it....

I was hoping for a way to get it working without resorting to disassembely especially since I don't really know what im doing...

obviously the asa and shutter speed dial send input to the meter needle, although I assume it is a electrical linkage rather than a mechanical one. (but I don't really know) I only have the standard prism for the (old) F1 I'm fairly certain there are no mechanical linkages between my prism and the camera.

I wonder if there are separate timers for the shutter at slow speeds and another for high? and yet another for the self timer? or are they a single timing mechanism?

As for taking the top plate off to "have a look", I might just end up doing this. I would start with the dial itself first. I have done such surgeries on Minolta's and Nikon's but not without pretty good documentation on how to do it. There doesn't seem to be much in the way of DIY repair available on the net for the F1. In the case of the other brands it was very important ti set the asa and shutter at a specific value prior to removing the dial (the repair manual did not comment on this)...