As per this thread, I have two old bakelite phones which are in good physical condition and currently in service as the primary telephones on each of my ADSL connections. These are standard telephones made for the Postmaster General's Department by AWA and STC.

My problem at the moment is that no matter how still the curly cord is, there is a crackling noise in the background. I know there is a condenser in the phones near the bell motor. Could this be the cause, and if so, is there a modern condenser it can be replaced with?

Everything else works fine, including the dials which I have cleaned until everything shines. The phone lines themselves are less than 1km from the exchange and are in very good order.

Do they have the old style carbon granule microphones in them? As I recall, the carbon granules when compacted can "fry" causing crackling and also attenuation/muffling of your voice. I used to give the mouthpiece a couple of good hand taps to break up the granules.

Hmmm, I will try that tomorrow and see what happens.

Taking the mike out of circuit is probably the fastest test.

Loose connection causing 90% of the interference on the wall phone. I'll see how things go next time I get a call on it.

Crackling handsets can be caused by carbon mike inserts, handset cords & loose connections. Handsets cords in 400 series phones can be a problem, especially in the spot where the cord enters the handset..Electronic replacement microphone inserts are available to suit 200/300 and 700 series phones:- www.antiquetelephones.co.uk Although 400 & 700 series handsets are of a similar shape there are some differences in where the mike insert sits. So a 700 series type electronic insert may not fit in a 400 series handset. A 200/300 series electronic insert will fit in a 400 series handset but will need to be packed to stop it from moving around.

The crackling has halved since I tightened the microphone connections. I might try a cord from a spare telephone and see how that goes. I have a few spare sets that I've wrecked for dials and the bits of bakelite that chip and crack, etc.

Report on progress to come.

The crackling has halved since I tightened the microphone connections.

I'd also try taking the mike temporarily out of circuit and see what, if any, effect that has on the problem.