Restoring a GPO 332 Bakelite Telephone

I've previously restored several old Bakelite GPO 300 series telephones and had a couple of people ask me to document how I go about it. I'm pretty bad at taking before / after photos as I tend to just dive in and dismantle the things before even considering taking a photo, so this time around I tried to get some photos before, during and after the restoration. I still got ahead of myself at times so the photos aren't quite in chronological order but I've tried to go back and fill in the gaps.

I aquired this phone from a seller on Facebook Market place along with a 232 Telephone and CB 935 Switchboard ( More info on those another day ). It was in reasonable condition but could do with some love to bring it back to its former glory.

The telephone, pre-restoration

 

 

Warning

GPO 300 series telephone were manufactured from ~1937 when we knew less about the dangers of certain chemicals and materials. The electronic components are known to have contained Polychlorinated Biphenyls (PCBs). Bakelite is made up of  Formaldehyde and Phenol, and according to some sources may contain asbestos - this is widely disputed, as asbestos would have been more expensive than the alternative celluslose based filler, but the possibility exists that the components were made in the same factory as other components that were using asbestos, so the inclusion or contamination can't be ruled out.

 

These materials are unlikely to be of any risk when the telephone is in normal use, but dismantling, cleaning and polishing the telephone may disturb something. Do your own research and risk assesment, and consider working on the phone in a well ventilated area with gloves and a mask.

 

Required Items

I'll probably forget to list something here, but you'll need the following items to restore a phone from start to finish:

• A GPO 332 Telephone
  
• Assorted flat head screwdrivers
• Small Torx screwdriver or allen key... about 1-2mm wide
  
• Needle Nose Pliers
• Adjustable spanner, or spanners in BA imperial sizes
• Basic digital oscilloscope
• 2x 1N4001 diodes
• 1x 3-3.3K 1/2W resistor
• Heatshrink / Insulation Tape
  
• Heatgun / Hair Dryer
  
• Soldering Iron / Solder
  
• Rags / Cloths / Sponges / Microfibre cloths. All the cloths. 
  
• Biological Washing Liquid for clothes
  
• White Spirit
• Greygate Paste Polishing No. 5
• Novus Plastic Polishes 2 & 3
• Bees Wax Polish
• Replacement dial label and cover
  
• Line cord with BT style plug if the phone isn't fitted with one.

 

Before photos

When I picked up the phone it was a little grimey, the dial was sticking and the curly cord had lost its curl, but it was otherwise complete. 

 

Disassembly

 

Phone Body

To disassemble the phone body you'll need to flip it upside down and access it from the bottom. I usually place it on a cloth or something soft to avoid scraping the Bakelite.

 

Firstly, undo the screw in each corner. You don't need to unscrew the feet in the rubber legs. The bottom plate should then just lift out.

Base of the phone, with screws highlighted

Next, remove the dial. Its secured with a small screw between the two bells. It's a little awkward to get out.

Posistion of dial securing screw

You should then be able to twist the dial body anti-clock wise to remove it. It's a bayonet type arrangement and only needs twisting 20-30° to remove it.

 

With the dial removed, take a photo of the wires connected to the back and unscrew them. Put the screws back in the spring-set so they don't go missing. Also screw the dial retention screw back into the dial for now.

 

Telephone body with handset removed

 

Flip the telephone upside down again and unscrew the 3 screws the secure the chassis in the body. Note, one is hidden by the large capacitor on the right:

Telephone with base removed with chassis screws highlighted

You can then lift carefully lift the chassis out from the phone which will reveal the gravity hookswitches. Undo the securing nuts, pull the hookswitches out from the top side and then put the nut back on for safe keeping:

Inside of telephone body with hookswitch securing nuts

With the case stripped, you can remove the handset and line cords from the screw terminals. Remove the wires from the screw terminals, making sure not to lose any of the screws, cupped washers or links. Undo the knots that secure the cords to the chassis - they tend to be tied in granny knots and have sat there for decades so they can be difficult to undo. I use something like a paper clip to slip between the knots and work them loose.

Telephone chassis showing original wiring

 

Handset

Disassembling the handset is fairly straight forward. The ear piece / reciever should just twist off with minimal force. If it doesn't I've found heating it up with a hair dryer will usually loosen it off. Bakelite is quite heat resistant so don't be afraid to give it some heat.

 

The mouth piece / transmitter cap is a bayonet style fitting and needs something inserting into the small hole at the top and with a small amount of pressure the cap should easily twist off in (anti-clockwise). I tend to use a small Torx screwdriver to insert into the hole.

With the caps removed, the transmitter will likely fall out or can simply be lifted out of the handset, leaving with you with something like this:

Handset with mouth and ear pieces removed

The reciever diaphragm (Yellow in the photo, but yours might be black) can be removed by carefully sliding it off. With the diaphragm and transmitter removed you'll end up with something like this:

Handset with diaphragm and transmitter removed

Remove the two screws that secure the reciever to the handset and put them somewhere safe. The handset cord wiring varies between cord types. The newer PVC cords tend to just have White and Green insulated wires and a metal cable grip thats connected to the red cable internally. Some PVC cords, and plaited cotton cords will have a red wire and a fabric loop that hooks around a cleat inside the handset. Take some pictures to help with re-assembly and undo the screws and middle pin, then remove the cord. I tend to reinsert the screws after disassembly to keep them safe.

Cleaning and Polishing

Once the phone has been stripped its time to give it a good clean. Unless its previously been restored it'll like have a film of dirt, grime and grease covering it.

First of all I give the body and handset pieces a bath in some hot water with Biological Washing liquid (The type used for clothes). Use a sponge to get rid of the dirt, but make sure you don't use it on your plates after.

Telephone going for a swim

 

Telephone, post-swim

Let the bakelite parts dry throughly before polishing. I  tend to use an electric polisher for this stage, but you should be able to get away with doing it by hand with a lot of elbow grease. I use Novus plastic polish, but you could also use Greygate Polish No. 5 or T-Cut / Brasso - anything thats mildy abrasive. You don't want to over do it, as in theory you might polish off the shiny outer layer and go down to the filler.

Polishes and heavy machinary

Post-polish you should end up with something like the photo below. Note in this example the Bakelite still has a somewhat mottled or flecked appearance. This is the underlying filler and unfortunatly this phone was like this when I aquired it. No amount of polishing will get rid of it.

Post-polish

Don't forget to also give the drawer front and small piece that secures the cords on the base of the phone. They may be made from Cellulose Accetate which is more delicate than Bakelite, so try giving them a gentle clean with soap and water before polishing. If they need it, you can use some Novus #2 Fine scratch remover to bring back their shine.

Next I like to cover the bakelite parts in a bees wax furniture polish and buff them to a shine. It's not always necessary, but it can help add a bit of shine to dulled bakelite:

Wax on, Was off. Telephone post-wax.

 

 

And the final result after everythings polished, waxed and buffed. By no means a minter but significantly better than before. Ignore the handset cord, I might have got carried away...

 

Polished phone body and handset, looking more like a phone

Whilst you still have the polish out, give the hookswitches a polish with Paste Polishing No.5  They're plated, so don't over do it or you'll go down to the brass underneath.

 

Restoring the curly cord 

The phone came with a PVC curly cord that had lost some of its curl and looked a bit worn out. Fortunatly they can usually be restored to their former glory or if you're looking for a more original look you can buy high quality replacement plaited cords. It's worth noting if you wish to use a plaited cord you'll need to check the handset has the cleat for attaching the cord to. See Sam Hallas's excellent website for photos of the various ways of fitting the handset cords.

Andy Cooper has an excellent video on fixing PVC curly cords. I've used his method on several curly cords and they always turn out great. The Tl;Dr is to drop it in warm soapy water for a while, give it a good wipe down with a cloth to remove any dirt, and then curl the cord backwards against its natural spiral to tighten up the curls.

Here's mine after washing and re-curling it:

Re-curled curly cord

 

Restoring the dial

Due to their size and being useful independently I've documented the cleaning and adjustment of a No.12 dial ( The dial originally fitted to the 332) in other blog posts:

• Cleaning the dial
• Adjusting the dial

If your phone has a different dial you might have to look elsewhere, or get in touch and I'll see if I can do another post for a different style dial.

Converting for use on a modern line

A standard GPO 332 that hasn't been altered since its original installation will need some adjustments to bring it more inline with modern standards. It's worth noting that the line you're attaching it to will need to support pulse dialing. Adapters exist, but thats out of the scopt of this post.

 

You will need:

• 3 - 3.3K resistor (1/2W)
  
• 2x 1N4001 Diodes
• Heatshrink or Insulation Tape
• Soldering Iron / Solder
• Heatgun / Hair Dryer
  

 

No. 205 Rectifier

Newer 746 telephones were fitted with with a "No. 205 Rectifier" across the receiver terminals to surpress any loud clicks that might occur when dialling or activating the hookswitch. You can create your own with 2x 1N4001 Diodes and some heat shrink or insulation tape.

Place the 2 diodes back to back, so the polarity of each is facing in the opposite direction, and twist the legs of one around the other. You only half a turn to keep them in place.

Replacement Rectifier 205 with leads twisted together

Solder each of the joints. The leads on my diodes are quite thick so I had to hold the iron on the leads for some time to get a good solder joint.

Replacement Rectifier 205 with leads soldered

Once soldered, trim the leads:

Replacement Rectifier 205 with leads trimmed

Add some heatshrink or insulation tape:

Replacement Rectifier 205 enclosed in heatshrink

Bell Coil Resistor

Modern phone lines expect a "high impedance" bell or ringer. To increase the impedance of the bell in a 300 series, we add a 3 - 3.3K 1/2 watt resistor in series. Add a bit of heatshrink or insulation tape to the main body of the resistor.

Orange, Orange, Black, Brown, Brown - 3.3K 

Wiring

With the components prepared you can now re-wire the phone. Remove any straps from the terminals, leaving a strap between T1 - T2 and T8 - T9 ( If they're not there already, use one of the straps you just removed to replace them )

Use the diagram below to help you get the line and handset cords wired up, and the resistor and rectifier in posistion. Once the cords are connected, secure them to the chassis again by tieing the strings around the chassis pillars. You want the end of line cords secured fairly closely to the chassis to avoid them being pulled out of the body and revealing the wires.

Wiring Diagram

 

Reassembly

 Body

Once re-wired you can put the chassis back in the body and do up the 3 screws that secure it in place. Double check there's no risk of shorts and that the resistor doesn't foul the bell clapper. You can bend the components and terminals a little if you need to move them out of the way of something.

Chassis back in the telephone body

 

With the chassis installed, flip the telephone upright and re-attach the dial using the photo you took as a guide. (You took a photo, right?) Mine looks like the photo below:

Re-wired dial

Once the dial is re-wired, remove the dial securing screw and insert the dial back into the phone body. To do this you angle the Number 5 posistion downwards, offer the dial up to the hole and line up the two mounts to the slots in the body. Once in posistion you can give the dial a firm push and it should slot back into posistion. Finally, twist the dial clockwise into posistion and re-insert the dial securing screw from below.

Assuming you've got everything right that completes the work on the body, so you can re-attach the based and secure it with the four screws.

Handset

To reconnect the handset, remove the screws that secure the wires and insert the handset cord into the hole in the base of the handset. Use the photos you took when you dismantled it as a guide to re-wiring it. Mine looks like this:

Handset with PVC cord fitted

With the wires re-fitted, place the transmitter back into the handset, carefully aligning the pin so it slots into the hole in the back, and then replace the bakelite mouth piece, then twist it clockwise to secure it. If it's loose or rattles, it can help to gently bend the metal tabs that secure the mouthpiece to the handset.

Screw the reciever back in place, and slide the diaphragm over the top. Make sure its lined up and screw the bakelite earpiece back on.

 

End Result

After scrubbing, polishing, oiling and adjusting you should be able to stand back and admire your handy work. I'm pretty happy with this one, it's not in mint condition but only needed a line cord, a dial label and a bit of love to make it look great again.

 

Finished Telephone 1

Finished Telephone 2