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New 17Mar2025, updated 22Mar2025. This note is in group Technology and My e-fun notes (electronics fun).

This note describes a hack which makes it possible to use a single cable with a USB-C connector in both ends and a USB-C power to charge the soundmaster IR65000SW radio. It would also go as a tip of how to approach similar problems.

Disclaimer

Don’t even attempt to do this if you don’t have a ton of experience with electronics modifications. For this reason you won’t need a detailed description since you’ll just know. The fact that it worked for me doesn’t guarantee anything for you. You would need your own experience to ensure that it will work for you. Be careful! Measure around before applying any power.

Maybe there is a newer version of the radio where this modification is not needed. I don’t know whether soundmaster has fixed this in a HW upgrade. I haven’t asked them. In that case they could have sent me a replacement connector board. This would have saved me the visually appearing downgrade..

You can also just use the USB-C (in the radio) → USB-A cable, then an USB-A → USB-C (for the charger) adapter (or cable) to solve the problem if you (like me) do want the option of a USB-C charger. The latter seems to contain the required resistors. Test this before you attempt my hack since it may save your radio!

Intro

For my radio it would only work if the cable has a USB-A connector at the charger end. The radio itself has a USB-C connector. The designers must have forgotten to add the required resistor(s) to make a USB-C source actually apply the 5V. That is, provided they were thinking that a USB-C power supply should be possible to use. If not, I guess they didn’t really «forget» anything as such. Even if using a USB-C connector in the radio indicates to me that a USB-C power should be possible. The USB-C standard requires a resistor for each up- and downstream power direction.

To apply higher voltages requires the USB-C charger to communicate with the radio over the wires intended for this. Inferring from the fact that it needed a USB-A at the charger end I don’t think this communication is done here. Plus the original text label «DC IN 5V» also implies this. Plus, for 5V it’s not needed. But I haven’t scoped it.

The radio draws max. 1A @5V. The red charging indicator in the radio changes to green when the battery is fully charged. Nice!

To fix the problem I simply added an Adafruit ID:4090 breakout board, see Adafruit USB Type C Breakout Board – Downstream Connection. It’s got the required resistors that tells the USB-C charger to deliver 5V at max 1.5A.

This radio is at soundmaster’s page as at Portable WLAN-internet/DAB+/FM-radio with Bluetooth®, rechargeable Li-Ion battery. I like it a lot, and its SW has even been updated from time to time. The last update I have is from Jun2024 (SW 20240617.1446). My «radio version» is 202207.0.1535.

But I was increasingly frustrated with not being able to use a cable with USB-C connector in both ends. The resistor I think they forgot to mount I have found no way to solder onto the original internal board since the USB-C connector’s wiring is by and large hidden between the connector and the board. This goes for CC1 and CC2 which are the wires I’d need. So I found no other solution than to add a connector instead. It was easy to test the concept before I started with the painful work. I electrically inserted the breakout board in an external cable and then used a USB-C charger. The charging indicator lit up as expected.

Here are some pages to read yourself up on this, to understand what soundmaster didn’t do and you don’t have to do either:

1. USB-C (Wikipedia)
2. Designing with USB-C: Lessons Learned (Apr 5, 2021 • matthew)
3. ALL ABOUT USB-C: RESISTORS AND EMARKERS (by Arya Voronova January 4, 2023)
4. Why do some USB C cables not work for certain devices? Is there a «right» kind of USB C cable to buy? (by Cease_Cows_, Dec2022)

But then, just using a ready made breakout board with the 5.1k (or other values) resistors is perfect!

I opened the radio and disconnected the wires and cleaned the connectors for old silicon or glue. I then carefully cut out the battery from the department (it was also glued). But this was after I had decided to fasten the breakout board onto the same battery compartment’s wall. I used 2.5 mm metal screws. But before that I had to make hole in the radio box itself. Since the USB-C connector does not protrude from the board I had to make the hole way «too large» to get the rather bulky USB-C connector’s «electronics box» safely sitting in place. The large hole was necessary.

(Thinking about it a second time while I write this I probably could have filed away the material that’s on the side of the connector and then made the connector protrude and then made a hole exactly the size of the original! Blush..) (Thinking about it a third time: that would have removed the fastening holes. It is perhaps more important with a sturdy mounting than a nice opening. Unblush..) (But there are other breakout boards).

I then soldered two wires from the breakout board to the original USB-C board. Plus and GND.

I then used silicon to fasten the battery and connectors again. Plus the «air» in the radio of my big opening I also filled with silicon. This also protects the radio from being filled with dust. (When the silicon has hardened it’s not as shiny as on the photo. And using a black marker pen or matte black paint on the silicon after a day or two probably is a good idea.)

Now I can use any cable in the new connector. USB-C ↔ USB-C or USB-C ↔ USB-A. Or even better: I don’t have to carry a USB-A charger or adapter for this only reason.

But there is not much use for two connectors, so I just masked the original with some tape. However, if I use a USB-C to USB-A adapter in the original connector (and USB-C or USB-A ended cable in the new) I can actually use the old USB-C connector for an extra USB-A (but not USB-C) output.

Again, don’t do this if you are not confident that you are 100% up to it! Don’t ever rely on luck!