How can I deal with a stuck shutter on a Rolleiflex Tessar 3.5 after storage in humid conditions?

1. Not Recommended:

There are ways that you could try and free it without dismantling and without touching it mechanically in any way. I'd guess that once you got it working at all it would improve over a few shutter operations - old lubricant can develop enough 'stiction' with time to overcome static forces but once freed up will usually not stick as solidly. But, it's highly likely that timing and reliability will suffer even if you do free it. See below for the 'perfect' solution.

I'd hope that if you cycle it between bright sunny spot and somewhere cool and if you try to operate the shutter a number of times on each move that after a while the thermal cycling will persuade the forces you apply to unstick it

2. Recommended:

However, as you are fortunate enough to be in Singapore the overwhelmingly best answer is "take it to Steven at "Camera Hospital", Sunshine Plaza, 91 Bencoolen St, Singapore. Phone:+65 6336 0025." The shop is on the outside rear of the Plaza - on the side away from Bencoolen Street - look for a shop with a large number of cameras in the window.

Steven will do as little or as much as you ask, will not charge enough for what he does and will renew your faith in camera repairers generally. Tell him that Russell McMahon from New Zealand recommended him to you. (Steven has repaired a number of cameras for me. My only involvement with him and his business is as a happy customer.)

If you look at the Camera Hospital web page here you may expect to see a large and bustling multiple employee store when you visit.

However, if you visit the Camera Hospital Facebook page here you will get a more accurate impression. A small store, window display jam-packed with heavy metal from days of yore (camera style) and a very small shop and one capable and friendly Steven.

Two apposite tips from his page

• Don't leave your camera and lens in your camera bag, store them in the de humidifier.

• The most inexpensive tip to keeping your camera healthy:
  Don't neglect it! Air it, use it under the sun... It's bought to be used after all ...

You'll find some customer reviews here - only 3 of them, but you'll a good idea of what to expect.