Bad Adapter Caused Malfunctioning Of Blue Tooth/USB/FM Player
This is a commonly available USB/FM/Blue Tooth player generally bought for fitting as Car Stereos. These are available as separate module as well as fit in a case like this. The box used is similar to those used for Electronic Choke. I bought this one for my testing as it has Blue Tooth too. Though this was giving some problems, I had no time to look into it and managed. When my son brought his Sony Component System, and wanted to have this module fit in the front case of CD Unit, as he did not want it, I removed this unit and fit it there.
Afterwards I bought a new module and fit it in this case and looked for the causes of power supply related problems. I opened the Adapter, which was luckily fit with four screws. I was surprised to see that a 1000mfd/10V capacitor, though the marking on the Adapter showed 12V. See the pictures below:
Just two diodes were found used along with this capacitor, on a centre tap transformer, the former of which was rusted already, though I bought this only a few months back. That’s the kind of quality of this cheap Adaptor. Anyhow, my job was to make it work perfectly and I went ahead with my usual rectification job. I replaced the diodes with new ones, connected 103 (0.01uF) fixed capacitor across the diodes, used a 2200/25V cap, used an SMD 5V regulator and soldered the heat zinc portion on the core, after scraping it clean. Added a 220/25V cap to the 5V output. Applied power and found that the 5V was perfect! Checked in Oscilloscope and found that there was no ripple! The DC was perfect!
As the DC jack was found loose, I replaced it with a better one that would fit tightly on the socket. Powered the Unit and found it to be working very well. I isolated the antenna wire and re-routed it through the top, ensuring that the wire does not come anywhere near the power supply or Audio output sockets. This was to ensure that the antenna is isolated and kept as straight as possible to avoid problems in FM reception. Here are a few pictures.
No, no, I would not forget to say ‘Mission accomplished and satisfaction got added to its ……………………….’ (LOL).
This article was prepared for you by Parasuraman Subramanian from India. He is 70 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous repair article below: