"These headphones are too loose and won't stay put." If that's the case, here are 3 "fixes."
1. If you make too many tuning cycles, the threads will eventually strip inside "Connector B" - the part that holds the rails to the headband with a single large screw. When this happens the headphones will not stay put and won't clamp at the same pressure as when you originally tuned them. This can occur slowly and you may not notice that the SQ is deteriorating. It can happen suddenly and the headphone falls off your head. There's a work-around using a 1 cm length of plastic coated wire tie - the kind used for closing bread bags. Fold it in half and place one end inside the compartment. The other side drapes over the outside at the 6 o'clock position.This works pretty well unless the threads are completely gone.
Connector B with a bread tie
I think it works better to reposition this bread tie 180 degrees so the outside of the tie is on the opposite side of this Connector B. Plastic covered wire ties work better than those covered with paper.
2. I'm working on a super glue fix similar to what works great for re-tapping the cup threads. Connector B's thread compartment, however, is much bigger than the cup thread compartments. Cup thread compartments filled/tamped/ with a paperclip/filled with super glue cure in 24 hours. Then drill them out with a 2mm (1/16") drill bit and the tiny screws will self-tap new threads in the remaining super glue that bonded with the compartment walls and floor. This method must be broken down across 3 or 4 days for Connector B. Fill Connector B's thread compartment by only 1/3 every 24 hours. By 96 hours you can drill with a bit no larger than the stock screw or use a tap and die kit to tap new threads.
I have not tried super glue "activator" that accelerates super glue curing. I'm going to order some from Home Depot Online and give it a try. Filling the compartment with super glue by thirds and using the activator between applications may speed the process up so the "fix" is completed within minutes instead of days.
NOTE: In order for Connector B to properly seat, flush, with the headband receiver, the new threads must be tapped exactly perpendicular to the horizontal plane.
3. You can order a new Connector B at fullcompass.com currently for $5.32 each.
If the link does not work, go the Full Compass web site and search: Fostex 1412000201 CONNECTOR B
OUR PART # 1412000201
Edited by bluemonkeyflyer - 10/22/12 at 5:03am
Connector B is #5 in the list.