I picked up a F nib Platinum 3776 from a seller on Ebay who didn't really know its history (estate sale).

It hadn't been cleaned in ages and was clogged up with what appeared to be brown ink.

I soaked the feed in soapy water for a while, cleaned the nib, put in a new converter and then it worked quite well. But it has a feed problem I cannot work out how to solve.

It will write for a about a page (A4) and then start to fade and eventually run competely dry. If I then carefully screw the converter down to refill the feed it starts to write again. But after a page or so it goes dry which seems to indicate that the ink is only coming from the nib holder.

I have taken the feed out and soaked in warm soapy water and it appears to be clean. I have even taken dental floss and run it along all the gaps between the fins on the feed. The first few times the floss came out brown indicating it was picking up the old ink but now it comes out blue (the colour of the ink I am using now).

The section looks clear and the converter looks like it's feeding ink okay.

Can't think what else I could look at. Any idea?

Thanks