Bingo! Fader replaced, board reassembled and working. I had never attempted this before and was a little trepidatious, thinking I might somehow render the whole assembly ineffective. I bought two items from Radio Shack to assist.
I found the desoldering bulb to be far more effective than the desoldering braid. I worked carefully and it all went surpisingly smoothly, much to my relief. I took no special precautions regarding grounding as I had not checked the forum before proceeding, but everything is OK as far as I can tell.
Many thanks for all the help.
Peter