Hello, I don't have in mind the exact image of the filters of PDP11, but in some case the filters are repairable in some way. The hard problem of course is to dismount it. Sometime these are stained iron foil boxes, filled with inductors and capacitors, then some gel insulator, and finally soldered with SnPb. Usually Rifa oil capacitors were used, which will explode after some years.
If you have some mechanical ability, you could try to open the filter case, desoldering it, or cutting on two edges, or removing bolts, etc. I successfully desoldered a filter of a Pro380, after it exploded. It took a couple of good hours to do the work, but now has new capacitors inside, and it seems like new. Andrea
