Fix for a Slow dial on 746 Telephones and 706 Telephones

Vintage 746 telephone and 706 telephone dials are lovely high quality mechanical devices (similar in many ways to antique clocks) however because they are mechanical they can start to run slow over time (usually many years). The instructions below explain how to clean/lubricate the speed governor in these antique telephones to fix a slow running dial.

Please note, a slow running rotary dial can cause problems dialling out if you are with some of the smaller telephone providers that use there own telephone exchange equipment such as TalkTalk (this is a very common problem).

To Access the Vintage Phone Dial Mechanism

1) Place a piece of sticky tape over the clear centre dial cover and pull if off quickly to safely remove the clear plastic centre dial cover.

This process is shown in the picture below:

2) Remove the paper label and then carefully unscrew the screw in the centre of the telephone dial, to remove the clear plastic (with a flat blade screwdriver).

3) Remove the small wire retaining clip from the vintage telephone dial, this is easily removed with your fingers (see the picture below)

4) Lift out the 746 telephone number plate backing out using a piece of sticky tape (as shown below).

5) The inside of the vintage dial will look very similar to the photograph below. However although the inside parts will be the same shape they may well be different colours and materials. This is because some parts of the vintage telephone dial mechanism may be plastic, others may be brass (especially in the older 1960's vintage 706 Telephones).

6) Then apply a small amount of thin "watchmaker’s oil" onto a cotton bud and use the cotton bud to clean out the dial governor cap. NEVER use WD40 as this will cause the dial to fail in a few months, its one of the worst thing you can use on these iconic vintage telephone dials.

IMPORTANT: Cleaning the telephone governor is far more important than lubricating, so make sure you are very patient and remove all the grime before lubricating.

Note: If you have access to a fully evaporating cleaning solvents (such as alcohol) clean out the telephone dial governor cap first before lubricating with watchmakers oil, again use a cotton bud for this. This extra step will ensure your vintage rotary telephone dial will remain at the correct speed for much longer than just lubricating by itself.

7) Move the cotton bud from side to side to get to the complete insides of the cup (see above and below).

8) Then replace the telephone Number dial backing (see below).

9) Replace the small wire retaining clip (see below).

10) Replace the clear plastic finger dial and centre screw and tighten the screw (see below).


11) Test that the vintage telephone dial rotates OK (to make sure the procedure has worked) and then finally replace the paper label and push fit the plastic centre cover. Then test the dial again.



All should now be OK with the vintage telephone dial. A simple repair on the UK's nostalgic 746 Telephone.

This process should work at least 70% of the time. However, if this procedure does not solve your telephone dial speed problem you may have to contact a vintage GPO telephone restorer for help or advice. Good antique telephone restorers should also have access to complex rotary telephone dial testing and speed / ratio calibration equipment.

When you buy any refurbished vintage 746 telephones most good telephone restorers should have already cleaned/lubricated and calibrated the dial so that they will work on all telephone lines, even from different providers with less forgiving telephone exchange equipment such as TalkTalk etc.

Once this task has been completed the telephone dial should give good reliable service for many years to come.

21A Microphone Replacements

The British 1960's 706 and 1970's/80's 746 telephones were made to last. I believe they were the last UK telephones that were designed so that they could be serviced and maintained for many years, not just replaced and thrown away.

The only weakness of these vintage telephones was the carbon granule microphone (transmitter inset No 16) used inside the telephone mouthpiece. These old carbon granule microphones degraded over time, resulting in crackling and noise that usually gets worse as the telephone conversation goes on. Looking at the photograph below the carbon granule microphone is on the left with a silver top and black base.

BT realised this weakness and started fitting electronic (electret) microphones in the early 1980's. These modern microphones were called "Microphone Insets No 21A". They significantly improved the sound quality experienced by the person at the far end of the telephone call as well as being far more reliable. The red microphone on the right in the picture above is a 21A microphone.

Collectors of old telephones will often pay a premium for these "Transmitter Inset No 21A" so that they can replace the old carbon granule microphones in their vintage 746 telephones, in turn bringing the speech quality up to modern standards, and improving reliability.

Original 21A microphones are hard to find in good condition. Of the few available spare 21A microphones in circulation many have suffered from moisture seeping into the circuitry, which results in a faint hum or buzz during the call which can be very annoying on a long telephone call.

To overcome this shortage of good quality 21A microphones several enterprising British telephone restorers have introduced a brand new equivalent electret microphone.

These new electret microphones were originally designed and made outside of the UK as replacements for the carbon granule microphones used in old American 500 series telephones. These 500 series antique telephones were the American cousins of our British 700 series telephones. However because the American microphones were physically smaller than the UK counterparts these new microphones have been augmented with a British designed and manufactured front/top so that they now fit snugly into 700 series telephones.

The photograph below show the front/top of these new microphones (on the right) as compared with the original 21A microphone on the left.

As you can see from the rear photographs below the new microphone (on the right) has a smaller diameter, however the British manufactured front/top prevents the microphone from rattling around.

The procedure below explains how to fit these replacement microphones using only a small flat bladed screwdriver (takes about 5 mins).


Step 1: Unscrew the mouthpiece cover.

Step 2: Remove the old carbon granule microphone.

Step 3: Unscrew the two microphone terminals and gently remove the two spade connectors.

Step 4: Pull out the metal retaining ring (be careful these are sometimes sharp).

Step 5: Attach the two wire to the modern electret replacement microphone. It does not matter which way round you attach them as they are not polarity sensitive.

Step 6: Fit the new microphone into the mouthpiece as shown in the two photographs below.

Step 7: replace the screw on mouthpiece. Sometimes it is necessary to be firm with the last screw turn as the microphones have a crimp up area to make them a snug fit.

Your vintage/retro telephone should now have as good if not better speech quality than a modern land line telephone.

Fix for 332 earpiece quite problem

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).

Safely Removing a Bakelite Mouthpiece

To safely remove the mouthpiece from a British Bakelite telephone handset (Type 164) used on both 200 series and 300 series Bakelite telephones, follow the following instructions.



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).

My Hobby (first post)

As a hobby I restore and renovate old British antique phones. I have a range of these vintage / antique phones, primarily GPO (General Post Office) phones dating from the 1920's to the 1970's. I limit myself so that I only collect genuine British Telephones. I have sympathetically converted these old phones so that they will still function properly when connected to a modern BT telephone exchange line. I do not believe the conversion of these Bakelite GPO Telephones diminishes their value, because I do not remove any of the original components, I just service and adjust them and only add a small number of electrical components that can be easily removed later if needed. I also have my own antique telephone Facebook site at Old Antique & Vintage Telephones . I also convert and restore these old telephones for other people.