Introduction: Cordless Hack Makes Portable Record Player More Portable
A few years ago I got a cool little portable record player for xmas. It’s great for hauling around the house and listening to records, the only problem is that you need somewhere to plug it in. With the weather here in Wisconsin becoming less Hoth-like, I wanted to take the music outside, so I decided to make the player battery-powered.
- Portable Record Player
- Rechargeable USB battery pack
- Heat shrink tubing (or electrical tape)
- Double-sided tape (or hot glue, etc.)
- Phillips Screwdriver
- Wire cutter
- Wire stripper
- Soldering iron
- Drill (optional)
Normally for this sort of project I would hot-glue a battery to the box and call it a day, but because I like the design of the player I wanted to preserve the original appearance and functionality as much as possible. Also I’m not the only one who uses it, so if I could make the change without changing anything externally (including how the power cord works) that would be ideal.
Step 1: The Record Player
This record player is sold under the brand “Innovative Technology”, but I’ve seen very similar players sold under other brands. The price seems to range between $50.00 - $100.00 with some slight variation in features. If you’re buying a player with the express interest of running it off battery power, you probably want to avoid extra features like USB, Bluetooth, etc. as these are likely to use more power and reduce battery life.
The first step is to identify what the power supply requirements are. This might be printed next to the power jack on the player or on the brick of the power cord. If not, you’ll need a voltmeter to measure the voltage directly.
If your player needs 5 volts DC, read on. If it needs anything other than 5 volts DC, the rest of these instructions won’t do you much good. You can certainly do this with a player that has different voltage requirements, but you’ll need to select a battery and charging circuit yourself, and if you can do that, you probably don’t need these instructions :)
The 5 volt supply is key, because that happens to be the same voltage as USB which means we can use an inexpensive USB battery pack to do most of the hard work of adding rechargeable power to the player. These battery packs have also become very inexpensive in the last year or so which keeps the cost of this modification down.
Step 2: The Battery
The battery I chose was selected because it was the cheapest one I had on-hand. I picked this up for about 15 USD over a year ago, I’m sure you can do better today. What’s important when selecting a battery is choosing one which has a separate jack for input and output, and one that can power a device while charging. Sometimes they include a USB cord which saves you the trouble of having to buy the one we’ll be cutting-up later.
The power-while-charging feature is important, because we’re going to wire the battery into the record player in such a way that it will always be receiving power from the battery’s output jack. If you want to listen to records with the player plugged in the wall when the battery is dead, you’ll need this feature.
I’ve never seen this capability described on the packaging so the only way I can recommend confirming it is to test it yourself.
Start by discharging the battery and then plugging a USB-powered device into the output side. Next plug the input side in to a charger and see if the device you plugged in starts getting power while the battery is charging.
Step 3: Disassembly
Time to open the player and see what we’re dealing with. In my case this was a simple matter of removing four phillips-head screws and lifting up a board that the turntable and controls are mounted to. It was snug, so I had to get a flat-head screwdriver and pry it up a little. Depending on your player, there may be more to this.
Once the board is loose lift it carefully because there will be wires connecting the parts on the board to parts mounted in the case (power jack, outputs, speakers, etc.). These wires connect to a circuit board using removable connectors that you’ll need to un-plug before you can completely remove the board.
Grasp the connector (not the wires) and gently pull each connector from the board (you may need to rock them back-and-forth slightly to loosen them up). Patience and care here are important, it’s the one place where a mistake can turn this into a much longer project (or a broken record player if you manage to break the board).
Once the connectors are loose you can carefully set the board aside.
Step 4: Prepare the USB Cable
Next we’re going to cut the USB cable. Exactly where you cut this will depend on where you want the battery mounted. I cut mine in the middle because it was long enough that either end would still reach just about anywhere inside the box.
Now that you’ve cut the USB cable you might notice that it contains four wires. Two of these wires carry the 5VDC the record player needs, but we’ll need to use a voltmeter to know which two. First you need to remove some of the sheath from the cable and strip the individual wires.
Start with the end of the USB cable that plugs into the output jack on the battery. If there is a black wire in the cable, connect the negative probe of your voltmeter; if not, select one at random to start with. Being careful to prevent the stripped wires from touching each-other, plug this end of the USB cable into the battery. Using the positive probe of your meter, touch each of the remaining three wires in turn and observe the measurement. When you see 5 volts, you have found the power leads. Make a note of the colors of the wires attached to the probes.
- If you see 5 volts on the meter, mark the color of the wire connected to the positive probe as +5VDC in your notes
- If you see negative 5 volts, reverse the probes and test again
- If you don’t see 5 volts, try selecting a different color to connect to the meter’s negative test probe and try again. If you repeat this 4 times and still see no voltage, make sure the battery is charged by testing it with a known-good device.
Once you know which color is +5VDC and which is negative you’re ready to wire-in the battery. You can trim the non-power leads of the USB cable or simply tape them up. I don’t know that there is any harm in simply leaving them exposed, but you don’t want to accidentally solder them into the circuit later so best to do something with them.
Once you have this end taken care of, repeat the process of removing the sheathing and stripping wires on with the other end of the USB cable.
Step 5: Wiring
Now we’re ready to connect the USB cable to the record player’s power leads. Take care not to get your wires crossed ? Take a look at the attached diagram to see how things will look when we're all done.
Looking into the empty case, you should see a pair of wires coming from the power jack, typically a red and a black wire. This is where we’re going to insert the battery.
Start by cutting this lead. Exactly where you cut it will depend on where you want to mount the battery and the length of the USB cable you’ll be using. In my case I decided to mount the battery to the left side of the box, so I cut the lead closer to the power jack.
Next you'll connect the end of the USB cable that plugs into the battery's INPUT jack. Solder the +5VDC wire of the USB cable to the RED wire on the INPUT side of the record player’s power cable (the part that leads to the power jack in the box). If you’re using heat shrink tubing to insulate the connection, be sure to put it on the wires before soldering.
Next solder the NEGATIVE wire of the USB cable to the BLACK power supply wire. Once the solder cools, insulate the connection using electricians tape or heat shrink tubing (if you’re fancy).
Repeat these steps with the OUTPUT end of the USB cable and the remaining power supply cable from the record player.
When you’re done you should be able to connect the USB cable connected to the record player’s power jack to the INPUT jack of your battery, and connect the other piece of USB cable to the OUTPUT jack on your battery. Finally, connect the remaining length of power cable (the one connected to the OUTPUT jack of the battery) to the record player’s circuit board.
To test the charging side of the circuit, connect the record player’s power supply to the power input jack and plug it into the wall. The battery should begin to charge. Next, connect the remaining power lead (the one connected to the battery’s OUTPUT jack) to the record player’s circuit board. You should now be able to turn on the record player and see it’s power light illuminate. If not, remove the power cord and double-check your connections.
Step 6: Charging Indicator (optional)
One problem with my record player is that the power jack is a bit flakey and doesn’t always connect right. This wasn’t a big deal when it was connected directly to the electronics because I could turn the record player on and wiggle the power plug until the power light came on. However, with the battery in the circuit the only way to know if power is flowing through the jack is by looking at the battery’s charging light. This works great, however I can’t see this light when the record player is re-assembled.
The best option would be to modify the battery so the charging indicator could be relocated to the control panel of the record player, but since I don’t want to modify the battery electronics (yet), I opted for something simpler. I simply drilled a small hole in the board containing the turntable above where the battery will be mounted. This allows light from the battery’s charging indicator to shine through when the battery is charging. It’s not easy to see, but it’s enough that I can tell when the power cord needs jiggling.
In the long run I’d like to do something more elegant, perhaps put an LED in the hole and wire it back to the battery’s charging indicator circuit but for now this does the trick.
Step 7: Reassembly
If everything in the previous step checks-out, you’re ready to put everything back together. You may want to temporarily reconnect the remaining wires between the case and the circuit board and try playing a record before putting everything back together just to make sure everything is correct.
Before closing up the case, you’ll want to secure the battery so it doesn’t move around when transporting the player. I used some strong double-sided tape to secure the battery to the bottom and side of the box, this makes the battery removable without requiring modifications to the case. A more sophisticated arrangement may be necessary depending on the size or weight of the battery. The important part is to make sure the battery stays put, and doesn’t interfere with the mechanisms of the turntable or cause contact with the electronics.
Once the battery is secured (as well as any errant wires) and the remaining wires are connected, slide the board containing the turntable and controls back into place and replace the screws that fasten it into the box.
Step 8: Wrapping Up
Initial testing with a partially-charged battery were positive. There doesn’t seem to be any performance problems when running on battery power (no speed issues, no volume limitations, etc.) and switching between AC and battery power is seamless. In addition, playback speed seems more stable now than it did using AC power, perhaps the battery is capable of delivering more amps for demanding moments in the music than the inexpensive wall-wart power supply?
With a fully-charged battery, I was able to play almost 8 LP’s (~360 minutes) of music at medium volume before the battery was exhausted.
I thought the first thing I’d need to do is upgrade the battery to something with a larger capacity, or perhaps something with a voltage regulator that could deliver more peak amps, but so far the cheap battery I’m using seems to have good runtime and meets the needs of playing the records I have at the volumes I desire. The beauty of this implementation is that should more capacity be needed, a larger battery can simply be plugged-in with no re-wiring.
A more sophisticated charge indicator would be nice, both in terms of indicating charging status and available capacity. It would be fun to expose this on the player’s control panel in a way that respects the overall design of the player, although it’s hard to imagine how to do that without making the entire project significantly more complicated. Solar charging might be nice to have, although leaving a record player in the sun is generally considered a bad idea. One thing that might make sense is to replace the barrel-style power connector with a USB jack and get rid of the power brick. This would allow charging from a lot more sources, and would also solve the unreliable connection of the stock jack.