Friday, 9 November 2018

Its not all Telephones you know!

Tuesday 6th November

By now most people will hopefully have seen the H&S Video which has been made required viewing by our Director of Safety, Chris Webb. In it he reminds everyone that all electrical tools which are used on GWSR property MUST be Pat tested and listed whether they are owned by the Railway or the property of an individual volunteer. Consequently we arranged that all of the mains powered tools which we may use in connection with telephone maintenance or installation would be brought in and tested. This particularly applies to our items such as portable power supplies, oscilloscopes and even simple things like soldering irons. Paul and I also tested the odd items often forgotten and found hiding in Locking Rooms like odd extension leads.

Meanwhile  Kevern was upstairs in Winchcombe Box contemplating mod's to the concentrator unit.
Later it was decided that the mod's could be done more easily and properly at his home workshop rather than balanced on the excellently painted shelf in Winchcombe Box. Oh wouldnt it be nice to have a clean Electrical Bench with good lighting to do this sort of fiddly jobs, Perhaps its getting nearer?.

After Lunch Paul and I went off to Toddington to look again at a Concentrator phone up by the Bridge which was worrying us and causing the signalman to get a false calling signal from time to time. This particular one is not often used but to us its still important that it works, you never know when it will be needed
 The line tested ok but the capacitor was only responding slowly to the standard ballistic test ie was leaky. Just old age I should think, I learnt long ago not to try changing components involving soldering on top of lineside cabinets. Since this is a non running week we will prepare another 706CB from stock and change it next week.

Incidentally next week is "Keverns Course". He promises to fully explain the circuit design constraints  within these concentrators. In the Mk1 and Mk2 units it was easy to be just loop Calling but as soon as we got Gotherington working to Cheltenham, we could see a design problem emerging. A lot of re-thinking around the design of the Box to Box circuits was needed .
Because they are bi -directional they are DC calling rather than the normal Loop calling of the standard SPT's and the ring current supply has to be automatically inhibited to avoid damaging the distant detection circuit. Should be an interesting session. He tells me that he will be using the newly completed box which is destined for Broadway as a training centrepiece.

Sorry its a bit wordy but hopefully some pics next week

Mike S

1 comment:

  1. Mike, if you connect the curly wire to the thing a me bob and dial 7 onto the exchange back circuit through the whatjamacallit does the phone ring in keverns workshop? Sorry mate but the above lost me, don't get me wrong but we do like the blog, just this one had us wondering what language from Star Treck was being spoken! Thanks for the update though.
    Paul & Marion.