Modifying BPL M9903-Two-In-One To House USB Unit In Place Of Tape
This two-in-one of BPL make was brought to me for servicing stating that the sound was intermittent and there were a lot of crackling noises. Working on a set made by BPL, in which I worked for almost 20 years, brought nostalgic memories and I was all in excitement!
As the customer was not interested in the Cassette Tape section to be restored, I suggested adding a USB input in its place, which he readily appreciated and accepted.
As usual, my work began with thorough cleaning after dismantling the whole set.
Replaced all the electrolytic capacitors on both the boards (the amplifier and tuner), and also the volume control.
Since the AC transformer was defective, replaced it with a suitable one and provided a 7808 regulator IC as this set required 7.5V DC.
Fixed a 7805 IC too on the same transformer for providing power supply to the USB module. 7808 was fixed on the side and 7805 on top of the TX (Transformer)
Removed the preamp IC and related components and also the protruding parts of the Tape Mechanism, and also the play wheels, to accommodate the USB Module. Removed the eject door, took it to a shop, where they do cutting of plastic parts for electrical fittings. Requested him to cut the eject door to mount the USB module from the front. He did a professional job, as usual.
Fixed the module on the door, wired its 5V power supply and stereo outputs to the preamp output tracks (Pin holes pierced – see picture below) of the removed IC, M51164AL. As I had routed the power supply through the on/off leaf switch of Tape Mechanism, it made things easy, as the customer can either use its own Tuner or opt for USB/FM pressing any of the Play/FF/REW buttons of the Mechanism, after selecting the function switch to Tape.
Switched on and checked and found the set to be working perfectly. I put all the parts removed for the sake of USB in a cover and taped it inside the Battery Compartment for future use, in case the customer wants to restore the Tape Mechanism. Here are the pictures of set working in USB Mode and the parts replaced (bundled inside a cover) and useful parts stored in the battery compartment:
You will notice from the above picture that the USB module was placed in such a way not to block any of the original symbols of the set! The customer reported that his entire family, especially the grand-children were very happy and amused to use this old set, with new features, which included blue tooth connection to their Android Phones! Satisfaction bag bulged further with one more added to it!
This article was prepared for you by Parasuraman Subramanian from India. He is 69 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.
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