Restored A Broken Amplispeaker And A Chinese Doll
Strange are the complaints that we, technicians get, and the gadgets/devices as well as the reasons for failures are also multifarious! Following are two such cases, brought by an Ayurveda Doctor (a recent acquaintance):
Case (1) : KDM Amplispeaker: The set fell down accidentally causing the charging port to rip off and the PCB getting dislodged. Let us have a look at this before proceeding further:
On opening the box, I found that the PCB had got dislodged, the cabinet was broken in a few places and the port was just holding on to its body on a remaining tiny solder contact. I just took it out and tried to fetch a replacement as the mouth was out of shape.
But I never got an exact replacement. So, I used a nose player and straightened the mouth portion to the extent possible, then connected a wire to the plus portion as the track was also torn. I used a helping hand to keep the PCB and solder the port in its place. Following pictures would help us understand it better:
Then fixed the PCB back in its position, and allowed the battery to get charged. The battery as well as the speaker was wired to the PCB through connectors and it was therefore easy to remove the board and carry out the repair.
When I played the gadget afterwards on USB, it played well. So, fixed the covers and kept it aside for collection by the customer.
Case (2) : Chinese Doll: This is a Chinese doll which shakes its hand when switched on and remains like that until switched off. It was brought to me with the complaint that the battery was getting drained soon and sometimes it works and sometimes it won’t. I opened the fixing screws and noticed battery had leaked to a certain extent.
The battery provides the power to a PCB on which a pasted IC is found. A coil sits on the other side of the PCB. The swinging arm is fixed with a bolt on a plastic screw, at the end of which is a permanent magnet square stone. The length of the plastic screw can be adjusted to bring the magnet close enough to the coil. When it is switched on, there is a pulse generated by the IC on the coil, making it an electromagnet. It then dispels the permanent magnet causing a swing. But it is balanced in such a way that it returns to its original position, but again dispelled by the electromagnetic field. The swinging movement reaches its peak on forward and backward movement because of the weight in the axle. It is a very smart way of applying electro-mechanical knowledge and I really appreciate the Chinese Guys’ brain! The following pictures give you closer look of the PCB and coil, which are an extract from the video that I took.
What did I do to solve the problem? I cleaned the battery leaks. Then retouched the solder points of the battery and connecting wires. That’s all! Fixed the doll back and tried. The doll worked very well and customer reported after taking delivery that it was working better than how it was when bought! Well, Chinese guys do help technicians like us to get laurels in this way! Don’t they? (LOL).
Missions accomplished causing a population increase in the collection bag! (LOL)
This article was prepared for you by Parasuraman Subramanian from India. He is 74 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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Albert van Bemmelen
May 11, 2024 at 4:46 pm
The swinging arm with the permanent magnet close the coil exactly looks like how my cheap but perfectly working QUARTZ clock with pendulum clock mechanism and Big Ben Chime works!
Parasuraman S
May 12, 2024 at 10:52 am
Ha! Ha! But we have to appreciate the electro-mechanism designed so perfectly! Should we not?
Yogesh Panchal
May 11, 2024 at 6:06 pm
Another Good fix!Sir
Parasuraman S
May 12, 2024 at 10:52 am
Many thanks, dear Yogesh!
Waleed Rishmawi
May 12, 2024 at 12:47 pm
I enjoyed your repair reports and a well done job on both. Thanks for sharing and many blessings to you my friend
Parasuraman S
May 12, 2024 at 3:54 pm
Many thanks for your continued encouraging words, dear friend! Crave to meet you once, provided the providence provides the opportunity!