Nicholas,
It is possible for you to replace these screws yourself. Here's what you need to do:
First, you will need to remove the black, round ring that has the serial number on it. This can be removed by using a friction wrench. This "wrench" is a round, black rubber tool, which looks like a large rubber cork. You simply press the wrench on the ring, and turn it counter-clockwise. This wrench can be purchased from companies that sell camera repair tools. Or, you can make one yourself. Go to your local hardware store. They sell rubber stoppers in different sizes. Purchase one that is the same size as the ring. You will have to remove some of the rubber in the center of the stopper, due to the curve of the front lens. Once you remove enough of the rubber so that the outer part of the stopper sits flat on the ring, turn the stopper counter-clockwise, and the ring will come off.
Then you will need to remove the front element. This can be done using a spanner wrench.
Once the front element has been removed, you will see 3 holes in the front tube. The 3 screws thread into these holes to hold the front tube on.
Once you replace the screws, you simply put the front element in, and then reinstall the black ring.
David S. Odess
Factory trained Hasselblad technician
28 South Main Street #104
Randolph, MA 02368
(781) 963-1166
