Photos of Phones and Phonographs (occasionally)

PAX Update


My last progress report on the PAX restoration was over a month ago.  I’ve made some significant progress since then – I just haven’t written about it.  Well, I say that.  I’m keeping a paper diary, I just haven’t managed to update here (mumble mumble busy at work etc etc)


So In the last month I have:

  • Repaired a couple fo damaged heat coils.  I’m pretty sure these aren’t a repairable part, and while my repair works electrically, I’m not sure it would stand up to the lighting strike they’re supposed to protect it from.  Mind you, I’m not planning on having any external plant hanging off this PAX so that’s probably not an issue.
  • I’ve fitted a wooden platform to the base of the PAX, to act as a shelf to hold the batteries, charging equipment and a more accessible connection box for connecting external equipment
  • Installed the batteries, with a removable connector to make it easy to isolate the battery supply if I need to
  • Fully tested all 4 selectors, I’ve identified two of them as having faults on the called subs side of the circuit.  One doesn’t pass ring current on to the called sub, and the other has a ring trip fault.  Neither passes speech.  This is hopefully just more relays to adjust.
  • Desoldered, cleaned up and re-wired a 60 pair “Box Connection” kindly donated by John Bathgate from the DFR
  • Desoldered the old 50 pair cable from the tagstrip at the back of the PAX
  • Mapped out the strapping on the tagstrip.  Which took ages, as there are 500 connections just for the line circuits (and another 50 or so for as-yet-unidentified-stuff)
  • Fanned out, laced, and wired in most of a new 50 pair cable from the box connection to the tagstrip on the pax (I left out the lines with unusual strapping until I understand how they’ve been strapped) – that’s what the photo at the top of the post is of.

I’ve still got a lot of work to go, but I’ve got 30 lines available and ready for phones so far.  I’ve identified 10 line circuits (spread across levels 3 and 5) which are all strapped for various forms of tie line functionality.  This is a bit odd, as from looking at the line circuits only 5 tie lines are fitted.

I really need to get my head around how the tie lines work, but my current working assumption is that it’s currently wired for 5 incoming and 5 outgoing junctions.  There are another 10 lines which have unusual strapping, that I haven’t yet identified (they don’t seem to match anything on the diagram)


That is one page of my strapping map.  There’s another page of it as well.  I’m hoping I can use that, combined with the wiring diagram and a series of train journeys to work out what on earth those last 10 line circuits do!

Oh yes.  And I’m building a PC that I can use to hook my PAX up to the internet.  More news on that when I’ve finished collecting the parts together.

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