A common error that occurs with the Sony WM-EX series Walkman is it playing for a few seconds and then shutting down producing four beeps from the headphones. I came across the WM-EX610 and WM-EX 674 cassette players, which did this and investigated the problem thoroughly by opening the players and checking all the subsystems.
This fault gets progressively worse over time until the player does not play at all. When pressing the play button, it tries to play but then sounds four beeps and shuts down. An error code of four beeps can happen for a number of reasons and if you are an electronic engineer, you may be able to trace the fault. The things to consider are the following.
Remove the Rechargeable Battery
These players use a NC-6WM rechargeable battery, which is a very thin square battery. Many call it a “chewing-gum stick” rechargeable battery. If you have left this within the battery compartment and forgotten about it, then it could be the reason for the fault.
Many people forget this battery and power the Walkman through an external AA battery holder provided with the player.
If you use both batteries together, then you can achieve an extended play time, however if the internal rechargeable battery is no longer charging or becomes defective and leaks then obviously the player will not work.
The first thing to do is to try powering the player with a new external AA battery. Obviously using a new AA battery helps to be sure that it is not a power issue.
Check ATS and Tape Switches
Check the “Tape” and “ATS” switches, to make sure they are making good and reliable electrical contact. Sometimes the copper contacts of the switch can corrode and a fine layer of oxide builds on it causing poor contacts. If these contacts intermittently break whilst a tape is playing then the player will shutdown giving four beeps.
Check the soldered connection to the switches on the PCB. Look for dry solder joints at the terminals of the switches. You can also solder a small jumper wire to by-pass the switches. This will help to determine if the fault is with the switch. I had a similar problem on one of my players where the fault was with the switch and a replacement was not available, hence I bypassed it by soldering across the switch contacts.
In addition, check the plastic levers on the “Tape” and “ATS” switches, because sometimes they may bend the wrong way round causing the switch to operate incorrectly. Sometimes they can fall off completely, thereby not closing the switch.
A slipping belt does not have enough torque to pull the tape. This will result in four beeps and shutdown. Usually cleaning the belt of any rubber residue will help the unit to operate fine for a short while; however, it proves that a new belt may be necessary.
It is also possible for dirt and dust to get into the mechanism through the tiny gap in the rotary volume cut-out slot, and as a result, the belt and mechanism may just need cleaning.
Faulty Stepper Motor
Sometimes the stepper motor can lose its pulling power or 'torque'. It simply cannot pull the tape and gives up. Sony no longer keeps stepper motors in stock, as this player is more than 15 years old, hence you will not be able to do much if this component has failed.
There is also a small optical sensor on the PCB component side, which senses the speed of a cogwheel on the mechanism side. This is part of the closed loop servo system connected to the stepper motor IC. If the optical sensor gets dirty or fails then the auto shutdown mechanism will trip. The sensor is a surface-mount device and very small.
Removing the PCB
If it is the stepper motor or the optical sensor that has failed then you will need to remove the whole PCB by removing the solder from several points to separate it from the chassis. It will be difficult and time consuming, however possible for those determined.
As the internal mechanism of the Sony WM-EX610 and Sony WM-EX674 are similar, it may be worth looking at both of my articles in the Vintage Walkman section as I have extensive notes and photographs showing the insides.
Check eBay for Parts
You could perhaps also look on eBay to see if there are any similar models for sale. A working one that is badly scratched and dented sells for a few pounds, and makes a good donor. You just have to swap the outer cases and you will have a working machine in a good condition. However, be careful when buying on eBay as someone else may have repaired theirs in exactly the same way and decided to sell the leftovers.