Intermittent Problem In MAXIL USB-FM-AMP Model-999 Resolved
This unit was provided by me to my wife, to listen to prayer songs very early in the morning and to play her choice from mobile through Bluetooth. This was having intermittent on/off problems and she wanted me to look into it using her special pass of liberty. I opened the set and cleaned it thoroughly and looked into to find that a 470uF/16V cap was bulged.
The 5.1V Zener also was found leaky. I replaced the caps and Zener, upon which the set worked flawlessly for a prolonged time. As I found that a regulator IC 7805, which had an input of 16V, was getting hot, I provided a 12V cooling fan to cover the area, which included the heat sink of the two Amplifier ICs. For the power supply, I used 7812 regulator which I soldered on to the transformer for heat dissipation and placed the fan on two rods fixed to the heat sink, and wired it.
But I forgot to add one each of 10uF at in and out, along with a 334 and 104 fixed caps, which I might add later, in case of a failure. I have done this in yet another LED TV, circuit of which was got from the web:
The Amp was tested for hours before closing the cover, to play songs sung by my elder son, which were so lovely!
Mission accomplished with special (whenever we do something to our relatives, it is considered as special!) double satisfaction which got entry pass into the collection bag!
The collection bag had a lot of achievements to brag about! (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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Yogesh Panchal
March 23, 2024 at 3:00 pm
Good Job! Sir
Parasuraman S
March 23, 2024 at 7:32 pm
Many thanks!
Albert van Bemmelen
March 23, 2024 at 3:47 pm
Adding those 7812 circuit components is of course a good idea but maybe it was also possible to remove the noisy fan and instead use the 12V regulator output for the 7805V regulator input that this way dissipates 4V times the used current less on power?
Parasuraman S
March 23, 2024 at 7:34 pm
I didn't want to overload the 7812 with the Amp current too! Many thanks for your expert comments!
Albert van Bemmelen
March 23, 2024 at 10:36 pm
Maybe if you use another regulator like the LM317T it easily handles currents up to 1,5A DC.
Parasuraman S
March 24, 2024 at 10:22 pm
Shall try next time! Thanks!
Tayo
March 23, 2024 at 6:06 pm
Adding a fan most certainly prolongs the life of electronics. I find myself adding one ?which i salvage) to many things i want to preserve. Well done Sir!
Interested in looking more into Albert's suggestion. Cant be as simple as adding a fan but it may have its uses in certain situations.
Parasuraman S
March 23, 2024 at 7:35 pm
Yes, dear! Many thanks!
Imoudu.O
March 24, 2024 at 3:19 am
Good repair sir.
Parasuraman S
March 24, 2024 at 10:22 pm
Thanks, dear!