Restoration

If your payphone has been in service for any length of time before it was removed, then undoubtedly, it will be suffering from some of the following;

Corrosion to the metal casing and/or Internal components
Scratched / Chipped / Smashed LCD window
Scratched / Cracked handset
Faulty Handset switch
Faulty Follow-On-Call (FOC) button
Faulty (Blocked) Sensors

This list isn't exhaustive, but it hopefully describes the most common problems associated with a second-hand CT54. Luckily, the Payphone is entirely modular and it is relatively easy to repair or replace any components that may have failed.

Corrosion

The CT54 has very little in the way of a corrosion protection built into its design. There are no sealing grommets or gaskets to protect against the ingress of moisture and as a result, corrosion seems to be a common occurrence. Typically, the front edge of the black casing where it joins the Stainless steel body is the worst affected area for rust. More often than not, the black powder coating has flaked off leaving the bare steel beneath exposed, which over time rusts.

It is relatively easy to restore the case back to its former glory though.

1) Lift the Payphone mechanism off its hinges and carefully put it to one side.

2) Using a heat gun or blow lamp along with a wire brush, remove the old black paintwork on the outside and strip the case back to bare metal.

3) Using some emery paper, rub down the case to remove any blemishes/rust spots etc. before preparing the case with grey etch primer.

4) Prime the case with etching primer. This is sprayed on and usually dries in 20 minutes or so. It may take a few layers of primer, lightly sanded down between coats to achieve a reasonable finish.

5) Finally, finish the case with either Matt or Satin Black car spray paint. I used Halfords Satin black on my CT54 which looks to be a close match to the interior paintwork but ultimately this comes down to personal preference. Powder coating would similarly provide an authentic finish to the case.

LCD Window

In most cases, the window that protects the LCD screen will have either suffered at the idle hands of someone's keys or coins and will either be significantly scratched or worse, shattered or cracked. Again, replacing the screen is very cheap and easy and provides a nice face-lift to a tired looking CT54. A replacement window can be purchased off eBay for as little as £2.50. The window is simply a piece of acrylic plastic measuring 50mm x 70mm x 6mm thick and a number of vendors sell custom-cut pieces if you provide them with dimensions. The edges of the window are un-polished.

To replace the window, perform the following steps;

Typical scratched LCD window perspex

Carefully unplug the 20-way ribbon connector from the rear of the LCD PCB by pushing the 2 lugs outwards and removing the IDC connector.
Remove the 3 nuts that hold the LCD PCB in place and store the nuts and associated nylon washers safely.
Gently remove the LCD PCB by lifting it off its 3 mounting posts and store it somewhere safe. (Try not to place the LCD PCB screen-side down since it is liable to get scratched or damaged and only hold it via the edges of the PCB).
Remove the 3 additional nylon washers off the mounting posts.
Now remove the 4 slotted round nuts that hold the metal mounting plate in place. These may well be rusted and require a short soak with some penetrating fluid before they can be removed. Either use some long nosed pliers OR a pair of small mole-grips to loosen each of the nuts.
Remote the metal mounting plate. If your payphone still has the coin-chute attached, the technique here is to ensure the plate is lifted off the mounting post underneath the coin-chute, last. Concentrate on lifting the plate off the 3 other posts first and once it is just clear of these, rotate the plate downwards towards the bottom of the payphone whilst tilting the top of the plate inwards towards the front of the payphone. It should then be possible to lift the plate off the remaining mounting post under the coin chute.
Remove the old perspex window and discard. There is sometimes a rubber gasket that sits between the screen and the casing - be careful not to lose or damage this if you do have one.
Clean the metal work and the gasket (if present) with a cloth and re-install the gasket before fitting your new screen window. The window simply sits in the recess of the casing and may require a little light sanding on its edges if it is too large to sit flush in the recess.
Re-fit the mounting plate, nuts, washers & LCD PCB in the reverse order, making sure not to over-tighten the nuts holding the PCB in place. If these are over-tightened, it may place stress on the screen or crack the PCB.
Finally, re-fit the 20-way ribbon cable IDC connector and close the 2 retaining lugs until they click shut.

LCD Display

The LCD display itself can deteriorate over time and this manifests itself with parts of the display becoming un-readable. A couple of examples are shown below. I don't think there's much that can be done to restore these back to normal though. The LCD assemblies are manufactured by Nan Ya Plastics Corporation and are mounted onto a custom made PCB.

Faulty LCD screen

Keypad

The Revisions A and B payphone are equipped with different keypads to the Revision C model, shown below.

Revision A and B keypad

Revision C keypad

The Revision A and B variants are equipped with a low-budget rubber membrane style keypad made by Devlin Electronics of Basingstoke. A common fault is for some of the more often used keys (e.g. 0) to become gradually more un-responsive due to contamination on the PCB. This can be rectified relatively easily by carefully dismantling the keypad unit and cleaning both the PCB tracks and the pads on the underside of the membrane with Isopropyl Alcohol.

In order to dismantle the keypad, using a sharp craft knife, carefully cut off the tops of the 6 heat-stake posts (1 in each corner + 2 in the middle of the PCB). Then the PCB will pop out of the plastic housing using a knife to carefully prize the 2 apart. Be careful on the corners since the mounting post holes are close to the edge of the PCB and it is easy to crack the PCB if you use too much force.

If, after cleaning, the keypad still doesn't respond, then the conductive pads on the underside of the membrane may require re-coating with conductive paint. This can be purchased on-line in small bottles. The paint is applied thinly using an applicator brush and allowed to dry for 12 to 24 hours before re-assembling the keypad and putting back into service.

Dismantled Keypad

Before

After cleaning

The keypad on the Revision C model appears to be more robust and I'm assuming this is why a lot of the CT54 Payphones are fitted with these. The Keypad is manufactured by Advanced Input Systems in the USA and has additional buttons to control Volume as well as to provide access to Email and SMS services.

The wiring harness for the Revision C keypad also differs from the Revision A/B keypads and the two are not inter-changeable without the necessary software version being loaded.

Revision 'C' - Keypad wiring

Handset Switch

If your CT54 fails to recognise the handset has been taken off-hook, then potentially, the microswitch has failed. This can easily be checked with a multi-meter or continuity tester between terminals 1 and 2. If the switch has failed, replacement is a simple job. The switch is made by the Swiss company SAIA-Burgess, model XGH10-81 but if you can't find this exact model, other variants will also fit. The key thing to check is the width of the spade terminals on the switch. The original switch has lugs that are 4.8mm wide and not the larger, more commonly found, 6.3mm lugs. If you can't find one with the smaller lugs, then it is possible to simply file down the connectors with a hand file to reduce the width down to the correct size. A replacement switch costs in the order of £5 or £6.

Handset microswitch

Note: The CT54 needs a connection to a working phone line in order for it to recognise when the handset has been taken off-hook. Without a phone line connection, the display will constantly alternate between "BT PAYPHONES" and "TO CALL LIFT HANDSET" even when the handset is off-hook. So if the handset microswitch passes the continuity test, then this might be the reason the CT54 isn't recognising the off-hook condition.

To replace the handset microswitch, follow these steps.

Carefully remove the two spade connectors from the switch. The wires are relatively thin and liable to break if pulled, so only put force on the metal connector itself.
Remove the two retaining bolts holding the metal handset switch assembly in place.

(The handset switch assembly consists of a metal frame with a clip-on roller arm, 3 x plastic insulating sheets, the micro switch and a spacer. These are all sandwiched together and held in place by the 2 retaining screws. Once the screws are removed, this assembly can be lifted out and dismantled.)

Insert the replacement switch, again sandwiched between 2 sheets of insulating plastic , then the spacer and finally the remaining insulating sheet. Make sure all the holes are lined up before inserting the 2 retaining bolts.
Mount the whole assembly back into the payphone and tighten up the two retaining bolts.
Finally, re-connect the two spade terminals to the 2 outermost terminals (1 & 2) on the micro switch and test to make sure everything is working.

Follow on Call (FOC) Switch

Follow On Call switch

The FOC button is a standard keyboard switch, more commonly found on older microcomputers such as the BBC Micro and Apple Macintosh Plus. The switch is manufactured by SMK and is one of their J-M0404 series key switches, also known as a Vintage Linear Type 4 (short stem, upright variant). This can also be picked up on-line for around £3.

The switch body is only clipped-shut, so it is possible to open up the switch and if it's broken, a repair may be possible. If it isn't then replacement with a second-hand one is relatively easy and only require some basic soldering skills.

Switches

There are 4 switches monitored by the CT54 Payphone;

Door: Switch to monitor whether the Payphone door is Open or Closed.
Vault: Microswitch contained in the Upper right corner of the coin vault.
Handset: Detects whether the telephone handset is connected or not.
Sensor5: Detects the presence of "Sensor 5", located in the coin tube.

Connections for the Door, Vault and Sensor5 are via the 10pin connector J6, located in the bottom right corner of the Interface PCB.

Door

It's not entirely clear whether this switch physically exists in the CT54 or if provision has simply been made in the firmware to cater for the potential future inclusion of a door switch. I seem to recall the earlier CT24 Payphone had a Light sensor (LDR) located in the middle of the main PCB and it was presumably this that was used to detect if the Payphone door was open or not. There does not appear to be any such equivalent on the CT54. Moreover, it appears that the Door contacts that connect to J6 on the Interface board aren't looped together by Sensor5 so the Door switch reports as being open all the time (see below).

Vault

Within the top right corner of the coin vault is a small microswitch that closes when a Container Cash No. 12 has been inserted into the vault housing. This microswitch shorts pins 5&6 together of the J6 connector to signal that the cash container is inserted and the vault door closed. Ordinarily, wiring of the vault switch is via a 2-way 0.062" molex connector wired via Sensor5. If however, Sensor5 is missing from your Payphone, simply wire the Sensor5 connector as follows;

Sensor5 (J6) wiring

Coin vault microswitch

Coin Vault Switch

In order to detect both the presence of a cashbox and the vault door being closed, a miniature Saia-Burgess V4T7Y miniature microswitch is mounted in the upper right of the coin vault and wired back to the Molex connector of Sensor5 (or directly back to J6 on the interface PCB). The switch is attached to the coin vault case via 2 small screws and is usually enclosed in a piece of heat shrink tubing to provide some protection to the switch contacts.

The closest replacement for this switch would appear to be the Saia-Burgess V4NCT7-Y1.

Coin vault microswitch

Handset

This switch isn't a physical switch as such but simply detects a loop on pins 1&6 of the Handset plug (J2) on the Interface board.

Sensor5

This is discussed in more detail below, but indicates whether the Payphone has detected the presence or not of Sensor5 , located in the coin tube.

Sensors

The CT54 has a total of 5 Infra-Red (IR) sensors in total that all need to be "Clear" in order for the Payphone to accept cash calls. The 5 sensors are as follows;

Entry(1): Located inside the Coin Validator assembly
Top(2): Mounted within the Scanway unit
Bottom(3): Mounted within the Scanway unit
Shute(4): Mounted within the Scanway unit
Sensor(5): Inside the square tube connecting the Payphone & coin vault underneath.

Sensor 5

It is not common to find this sensor with an old CT54 since I guess when the Payphone is removed from service, only the Payphone itself is recovered and the coin vault assembly and the connecting coin "tube" (containing the sensor) are recovered separately. The good news though, it's a simple job to make a "fake" Sensor 5 in order to fool the Payphone into thinking it's clear.

You'll need a 3mm Infra-Red LED emitter and a 3mm Infra-Red Receiver LED. Wire the receiver across pins 7-8 and the emitter across pins 9-10 (see diagram above) taking care of the polarity of each LED. Also, strap pins 3-4 together. This will cause the LED emitter to start pulsing at a rate of around 1 flash per second. (This can be checked using a camera on your smartphone). Once the Emitter and Receiver are aligned with one another, the status of Sensor(5) in the Test menu should change from being BLOCKED to CLEAR. If all is working, slide the LED's into either end of a drinking straw or a piece of heat shrink tubing, so that the lens of each LED is facing each other, then run some longer wires back to the correct terminals on J6.

The purpose of this sensor is to detect for blockages within the coin tube and I am assuming this is also used to detect when the coin vault is full. Coins would start to back-up the tube, thereby blocking Sensor5. So what is Sensor5? Simply put, it comprises an Infra-Red emitter and receiver LED that are aligned with one another such that as coins drop down from the Payphone to the coin vault, they momentarily interrupt this beam.

Should Sensor5 report being in a "Blocked" condition and there are no visible blockages, then it's more than likely the IR LEDs need cleaning to remove any dirt or dust that may have accumulated and preventing the IR beam from reaching the receiver. This can be achieved by using a cotton bud dipped in some Isopropyl alcohol to clean the lens of both LED's in the sensor.

Sensor5 Wiring

There is an additional 2-pin Molex connector below J6, labelled as J7. This connector is a replica of Pins 9 and 10 on J6 and is a suitable testing point to check for the presence of a pulsed-output voltage using a multi-meter or for connecting a standard 3mm Red LED for visual testing purposes.

J7 connector

Locks

The Payphone and Cashbox locks should be regularly cleaned and lubricated with a good quality cleaner. The cashbox lock is manufactured by dormakaba who also sell a lock cleaning aerosol that lubricates, cleans and inhibits corrosion.

Recessed Keypad Paintwork

The keypad buttons and the graphic underneath the keypad, are highlighted in blue paint, which tends to get worn away over time. The nearest match to the existing paint that I've found is Humbrol Midnight Blue (No. 15), Gloss enamel. Using a small paintbrush, dab in the paint to the recessed artwork and buttons where it has worn away. The most effective method I've found is to then carefully scrape off any excess paint using a piece of card and then wait for the paint to completely dry overnight. Using an oven hob scraper tool, remove the surface paint which should leave the recessed paintwork intact. An alternative approach is to wait for the paint to flash-off and wipe off the excess with a cloth and some white spirit. However, since the recesses are so shallow, I found it invariably removes all of the paint work completely.

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