Wednesday, December 24, 2008
1) Firstly NEVER EVER Spray WD40 or other oil directly into these old dials. The backing to the dial number plate (seen on photographs below) is similar to emulsion paint and is VERY porous. WD40 or other lubricants will soak into this, badly discolouring it and most likely destroying part of the numbers. We see more dials badly damaged by people doing this than any other cause.
2) Using a very small flat bladed screwdriver carefully prise out the metal circlip that holds the paper dial label insert in place (usually covered with a plastic clear label cover).
3) Remove the clear cover and dial lable to expose the centre screw.
4) Next remove the CENTRE screw (and only the centre screw) with a flat bladed screwdriver, and lift it off the chrome finger dial.
5) Carefully remove the larger circlip holding the number plate in position (looks like piano wire). I do this with a compass point, and I think this is the fiddliest part of the procedure.
6) At this point the dial number plate can be lifted out exposing the inner workings of the chrome dial.
7) Notice in the next photograph (below) the back of the dial number plate, which is the porous backing that WD40 or other lubricants will absorb into, and permanently decolour and damage. Be VERY careful not to get any oil near this part.
8) Use a cotton bud to apply (very sparingly) a small amount of watch makers lubricating oil or graphite to the inside of the governor cap (see below).
9) Next use a cotton bud to apply (very sparingly) a small amount of watch makers lubricating oil or graphite to the gear teeth (see picture below).
10) Reassemble the dial in the reverse order.
11) If you have been successful you should be able to dial a “0” and in the time it takes to say (at a steady pace) “one thousand one hundred and one” the dial should return to its rest position.
Thursday, October 09, 2008
An old GPO engineers maintenance trick for fixing the problem of the earpiece being quite on an early Bakelite 332 telephone is as follows:
1) Unscrew the bakelite earpiece (anticlockwise)
2) Slide the metal diaphragm (thin metal disk) sideways off the earpiece magnets (make a note of which way round it is)
3) Make sure the two screws either side of the magnet are tight.
4) Spray the metal diaphragm (both sides) with a small amount of WD40 and wipe off with a piece of paper kitchen towel.
5) Replace the metal diaphragm (the opposite side up to the way it was removed) by sliding it sideways back onto the magnetic coils.
6) Screw the bakelite earpiece back on.
Then try the telephone again and see if this improves the sound (works about 50% of the time).
Sunday, July 20, 2008
1) Carefully insert a fine pointed instrument such as a compass point or probe from a multimeter (as shown below) into the release hole of the bakelite mouthpiece. Be very careful not to damage the bakelite.
2) Applying gentle pressure to the release spring inside the mouthpiece rotate the bakelite mouthpiece anticlockwise by 1/2 an inch (as shown below).
3) At this point the bakelite mouthpiece should just lift clear of the main telephone handset.
4) The carbon granule microphone is now exposed.
5) Replacement of the mouthpiece is simple, just put the bakelite mouthpiece on and rotate it 1/2 clockwise (if adjusted correctly it will lock onto the telephone handset).