Substitute Electronic On/Off Switch Provided In Sony Radio
This Sony Radio ICF-570 was brought to me by a technician friend of mine, with the complaint that the press to on/off section is not working and as the IC was not available and he wanted me to replace it
with another circuit. Well, such challenges would always evince great interest in hobbyists like us and I started the work right away! As he had already opened the set, cleaned and gave me the screws in a separate packet, that portion was saved!
I removed the IC from the board. The IC number used in this radio was HW9315, but showed BU2305F in the circuit diagram, from the service manual downloaded from the following site:
Since the number was not clear enough, I clicked three snaps using different settings:
Located a good latching circuit from the following site:
Since I was not having IRF7319 IC with me nor was it available locally, I connected two separate mosfets of P Channel and N Channel (Any number would do that would work in low voltages. I forgot to note down the Mosfet numbers), in a bread board and tried. It worked very well! First I tried it giving the power supply itself as the load and connecting a Multimeter at the output. Then replaced it with an LED connecting a current limiting resistor in series. I connected it to the Radio too and it worked.
Having tried and confirmed that the circuit was ok, I ordered for 10 Nos. of IRF7319 to AliExpress, got it delivered within 25 days through post. Soldered ‘octopus’ legs on it, then once again tried it on a breadboard. It worked very well.
I removed all the SMD components from the Board of the Radio and with a lot of study and care, populated that area with regular components, as SMD was not available. The work looked very crude, as my aim was at the result!
Rechecked the connections and gave the power, it worked very well. It is important that we do connect a 10K Resistor and a diode at the output, without which it did not work, because of the capacitive load on the Radio.
Fit the Radio and tried it out several times, with a lot of amusement such as a child will have, when its invention or modification of a toy works well!
Another proud service-cum-project work added to my ever bulging satisfaction list!
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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