Minidisc Deck Auto Track Mark

For MDS JE530 - MDS JB920 - MDS JB930 - MDS JB940 - MDS JB980 and many others....player


Version Française

The problem :

If like me, you want to record music (or wathever) from the radio or another source when you are away or sleeping, you will end up with a MD with one very long track (up to 320 minutes in MDLP 4) which is not very convenient !

The solution :

Almost every Sony Minidisc deck allows you to add a track mark while you are recording something by pushing the REC button. What we will do is simulate electronically the push of the record button at a user defined interval. So when a 80 minutes MD is recorded in LP4, you will have 107 tracks if you (like me) choose a delay of 3 minutes, wich will allow you to skip songs or adverts you don't like when you will play the minidisc...

I did this project on my Mini Disc Recorder MDS JB940

I record from Solar Radio on my Humax 5100 satellite receiver on Astra 2 every night

What do you need ?

Very basic electronic knowledge, a screwdriver, a soldering iron, etc...

The theory

The 555 ic sends a pulse (approx. 0.5 sec) at a user-definable period (I used 3 minutes for mine) to the reed relay wich acts just like a switch. We will connect the output of the reed relay to the pins of the record button inside of the deck, on the PCB circuit.

Let's make it !

You can maybe take 5 Volts inside your deck to avoid building a regulated power supply but I did not tried this for obvious reasons.

Example of a power supply


T1 Transformer, 110 or 240 vac primary, 12 to 6.3vac Secondary
BR1 Bridge Rectifier 0.5 Amp
C1 Capacitor, 1000 uF @ 16 vdc
C2 Capacitor, .01 uF
IC1 Integrated Voltage Regulator, LM7805

My auto track mark circuit 


IC1 : 555 (CMOS Version)
RLY1 : VR05R051 'A or Equivalent 5 Volts Reed Relay
C1 : 100µF C2 : 47µF C3 : 100n C4 : 10p all 16V
D1 & D2 : 1N4148 or 1N914
R1 : 22K R2 & R3 : 1M R4 : Trim 500K All 1/4 watt or more
A little piece of perfored board

More info about the 555 IC here, there and the data sheet in .pdf  (128 K)
More info about the VR05R051 'A Reed Relay here    
Where do I solder the two wires inside my deck ?

Open your deck (remember this could void your warranty!)
 and look for the keyboard/display pcb just on the back of the record button.

You will find very easily the two pins of the record button, just solder properly the two wires, find a way out for them and close your deck again.

Here is an example on the MDS JB920 PCB

Some photos of my MDS JB940 :



You can experiment with different value of C1 and the 3 resistors R2+R3+R4 for longer or shorter delay.

To get a 3 minutes delay, experiment with the value of the R4 trimmer.

Also, there are programs that will calculate the delay for you (Windows), dowload one of them here

You can put the circuit in the Timer case if it is big enough or in a plastic box.

It is best to take the main power at the same source as the deck so they wake up togeheter !

Due to the 555 design, the first pulse will take longer than the following one. For a delay of 3.00 minutes, the first track is 4.50 minutes.

The accuracy of the circuit at startup is about 1 or 2 seconds maximum for a 3 minutes delay but after about half an hour, you get a stable 3.00 minutes delay.

You can put a switch between the relay and the record button for non timer usage.

For automatic operation with my Sharp Optonica Timer (from 1981 !), I put the 1 wire of the output relay via the Outlet "A" ON/OFF switch (bottom left on the photo below) which is a double inverter (6 poles) with one side not connected. So I connected the wire from the relay (it doesn't matter wich one of the two !) to that unused side of the inverter and when I switch the deck ON manually the MDS JB940 by pushing the Timer button "Outlet A", the deck will not receive the pulse from the relay (for normal operation) . If the deck is switched ON by the timer, the Outlet A swtch is not pushed and then the inverter will pass the contact between the relay and the record button for Auto Track Mark.

I also put a on/off switch at the back of the Timer to allow me to force the pulse to pass even if I switched manually the Outlet A switch.

Of course, it all depends of the Timer you use !

Let's just hope that Sony will include this function in their future deck, like they just did on their MZ-N10

Sharp Optonica timer with the Auto Track Mark inside :


I hope I did not make any mistake on this page !

Do all this at your own risk but don't worry, I've got e-mails from all over the world telling me this circuit work great !

I've done my best to make all this as clear as possible but if you have any questions...


Last modified : 12 may 2004
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