449
Item nr.
Failed Stereo project.
Production | The Netherlands, 2017. |
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Bands | FM. |
Cabinet | Plastic. |
Power | AC 230V. |
Documents | Plan. |
Obtained | 1/2017 from Scrap parts. |
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Condition | 5. |
Disposed | Scrapped 1/2017. |
In the side of the master speaker I sawed an opening and mounted the 747D unit. I added an L7805 voltage stabilizer to supply 5V to the unit, from the buffer elco of the amplifier. My idead for the final unit was that it could be used in Mono mode (just the Master) or Stereo (with the slave also connected). This worked more or less OK, I immediately got sound from the speakers and I could use the remote control, and play radio and MP3 files as well. Problem was that the pulsed current drain from the FM/MP3 unit caused a heavy noise in the amplifier! That this was really power induced I could verify by turning the amplifier volume control to zero: a nasty humming beep sound could still be heard.
When I tried to fix this with some extra elco's and tested with an external power supply, the 747D suddenly went black and broke down completely. After this failure, the processor chip immediately runs very hot after applying power.
And this was the second unit dying on my workbench within a week! A few days earlier I had tried to built one into my Sloper set, and that one also broke down while I tried to fix some problems. My conclusion to date is that these units are not very robust. A follow up project must have better power supply, perhaps even completely separate from the analogue parts of the project.
After failure of this project, I reworked the remains into a little micro amplifier, which was subsequently used by my offspring with BNS E12 speakers (60W).
A few years later, I did some more projects with Bluetooth sets and then they were very successful.