Odd Software for Odd Jobs

Adding DC power output to my "boombox"

So, I added an AUX-IN to my old Sony boombox. I can now connect my MiniDisc recorder or iPhone and play my tunes, as well as listening to tapes and CDs … oh, what a time to be alive!

I had been running my MiniDisc recorder off a single 1.5V AA battery but wondered about adding a DC output also to the boombox.

The radio tuner section that I have commandeered for my AUX-IN receives 6V from the main board. The MiniDisc recorder takes 3V from an external supply.

I started by figuring out what type of plug the Sony takes … the "Sony yellow tip barrel connector".

Turns out it's a 0.7mm (inner diameter) x 2.5mm (outer diameter) plug … Jaycar catalogue PP-0503. Also known as the "Nokia plug" apparently. Never knew that!

I'm going to use a 2.1mm plug & socket on the other end. So I made up a short cable.

2017-05-04 21.13.42

The first step was to see how much current the MiniDisc recorder would be drawing. I hooked it up to my lab power supply and gave it 3V … it drew about 300mA maximum (when first spinning up the disc and reading in the 10s of audio for the buffer).

I did muck around with regulators but gave up (I'm not clever enough). It's possible to get a 3V regulator but it needs at least a 3V headroom … with a supply of 6V that might be okay … in an "ideal" world. I didn't have any of those handy or easily available. I do have 3.3V regulators … a LM2936 and LM3940. The LM2936 would've been nice but it can only supply 50mA - not enough. I did fiddle around with an LM317 as well but I could never get it to work.

Besides, regulators are inefficient and I'm not sure how much current I'll be able to draw using the tuner's power rail.

There is a 3.3V rail available for the CD player, but I assumed that it wouldn't be powered if the radio tuner (i.e. AUX-IN) was selected. Maybe it is, dunno.

So I just used a more efficient DC buck converter instead! Simples!

2017-05-04 20.59.45

Stuck 6V in, tuned the trimpot to 3V out.

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And the MiniDisc record is happy!

2017-05-04 21.12.45

Checking the service manual again, I could see that +6V and GND were available here - there's a 0Ω link (JC1) for the +6V and a spot next to capacitor C58 for the GND … these are probably the easiest spots to tap in.

File 5-5-17, 12 25 42

There's no convenient hole like there was for the R + L channels, so I just drilled my own.

File 5-5-17, 12 26 09

Hacking away … new DC power output added to my earlier AUX-IN addition.

Honestly, it'd probably be easier if I just made my own replacement radio tuner board … bonus points. Need to check if I can get a similar flat flex connector.

2017-05-05 10.41.23

New hole drilled for the 2.1mm DC power socket.

2017-05-05 10.47.52

The AUX-IN and DC power sockets mounted.

2017-05-05 10.52.34

Jamming the 6V-to-3V converter in.

2017-05-05 10.58.28

Power out … and audio in!

2017-05-05 11.11.43

Sony never meant for this to happen, but their CDF-S350 is now powering their MZ-NH600 as well as taking audio in from it.

2017-05-05 11.11.52

Drawback - the audio and DC power share ground … so you hear digital noise when the MiniDisc recorder is starting up and when you change the song. This noise is not evident when playing, however, so I'm happy to live with it.

Adding AUX-IN to my "boombox"

We've got an "old" Sony CFD-S350 portable radio/CD/tape player (i.e. a "boombox"). So it doesn't really get much use any more - but if it had an AUX-IN then we could hook our MiniDisc or iPhone … or anything … and still use it.

2017-04-23 05.07.12

Pulling it apart …

2017-04-23 21.13.10

Disconnecting the flat flex connecting the CD unit and button controls from the main controller board

2017-04-23 21.12.22

2017-04-23 21.09.18

Removing the tape unit and speakers to reveal the radio tuner board …

2017-04-23 21.07.43

I still want to play the occasional tape and CD … but I don't really listen to radio, so let's see if there's something there I can use …

2017-04-23 05.07.12-3

(I've noticed that the Japanese use the Icelandic letter Ð instead of just plain D … makes sense as it prevent confusion with the letter O or digit 0!).

So there is a left & right channel coming into the main controller board (and amplifier I assume) that I could connect my AUX-IN to!

This is the radio tuner board with the flat flex connector on the right.

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The IC is a Toshiba TA2149-series … and the data sheet tells me these are the R & L channel outputs:

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Following the trace confirms that they run directly to the flat flex connector with nothing else in the way:

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I found the service manual for the CFD-S350 and noticed that there are two 0Ω resistors being used as links … so I could simply remove them, disconnecting the decoded audio from the radio tuner chip and hook my AUX-IN socket:

2017-04-23 17.39.18

Careful …

2017-04-23 20.50.14

Now hooking in my AUX-IN socket …

2017-04-24 13.08.44

Drilled a hole in the side of the case for the socket and put everything back together:

2017-04-24 17.11.46

2017-04-24 13.11.22

New life/use given to this still-working-fine piece of equipment!

2017-05-03 09.37.35

Bonus point … there's a 2Kbit CAT24WC02 serial EEPROM on the the underside of the main controller board … IC805, top right … that uses the I2C bus. I wonder what's on it … ? Maybe I could use an Arduino to read the contents?

2017-04-24 12.36.10

Replacement Sony MiniDisc remote, part 2

The RM-MZ3R MiniDisc remotes I ordered on eBay arrived today so I got to work pulling one apart to start figuring out how to emulate one so I could have a nice large control box rather than a fiddly little remote.

MD remote2

It's simply a bunch of resistors (and one capacitor), with the audio L/R channels passed through.

MB remote1

The audio uses three wires - ground (brown), left (white), right (red). The controls use two wires - grey (KEY) and yellow (+B). Two remaining wires were cut short and not terminated on the circuit board - these, I assume, are for the display information (the RM-MZ3R doesn't have a display).

The resistor values are:

  • R1 = 1KΩ
  • R2 = 1.3KΩ
  • R3 = 1.3KΩ
  • R4 = 47Ω
  • R5 = 1.5KΩ
  • R6 = 62Ω
  • R7 = 2KΩ
  • R8 = 1.3KΩ
  • R9 = 1.5KΩ
  • R10 = 2KΩ
  • R11 = 2.4KΩ
  • R12 = 2.4KΩ

There are ten switches:

  • S101 = hold switch
  • S102 = reverse, select left
  • S103 = FF, play, select right
  • S104 = pause, CAPS
  • S105 = stop, ENTER
  • S106 = VOL -
  • S107 = VOL +
  • S108 = TMARK
  • S109 = DELETE
  • S110 = EDIT

Various combinations of the resistors lead to the MD unit understanding what command was sent. This is what I'm working on now (yes, I can just find it on the Internet but I learn more this way).

To make it easier, I've removed the wires from the circuit board and replaced them with headers. I've also soldered the tiny wires onto a breadboard in preparation for tinkering with an Arduino. I used a hot glue gun to try to make the wires a bit more robust - let's see!

You can see the two shorter wires on the right - these are for the display information. Should be interesting to figure out how that works.

2016-02-15 20.32.23

I'm almost ready to start tinkering …

MD remote3

Project Idea: Replacement Sony MiniDisc remote

A project idea to exercise the brain - replace the RM-MC38EL remote control on my Sony MiniDisc recorder with a larger unit.

2016-02-01 06.47.07

It would use a larger and easier to read 16x2 LCD and buttons controlled by an Arduino. This will make it more like a component unit and make it easier to use in my workshop than the fiddly little controls it has now.

Sony never made a component HiMD.

The hardest bit will be the plug - either cannibalise a remote or somehow simulate it? Two pins are used to send commands to the MD (different resistance for each command) and the other two for sending data to the remote's display (will need to figure that out!). It does appear easy to acquire Sony RM-MZ3R remotes on eBay, giving me access to a source of the plugs. It would be nice to have just the four-pin plug, leaving the headphone socket free.

I did find a similar project that pre-dates Arduino. In this case it was to allow the use of infra-red remote controls.

Might turn out to be another dead-end ... but it is fun to experiment!