ON-OFF Volume Control Found Broken In SONASHI USB-8 Band Radio-SRR89
This radio was brought by a new customer (a super senior citizen living close by), recommended by one of my regulars. The complaint was that the on/off switch was intermittently working. I opened the set and was surprised to see that it was very clean inside!
Let us have a look at the inside of this 8 band radio with USB & Bluetooth connections and see how it used a single chip board with an internal rechargeable battery:
I checked the on/off-volume switch and found that it had developed a crack of the case and it was not making proper contacts. I removed it, which came out in pieces and fetched a replacement later in the day. The single chip used in this radio was KT0936MB9, datasheet and video of this wonderful single chip can be found with the following links:
https://maximradio.altervista.org/kt0936m/KT0936m_b9_v2.2-english.pdf
Let us have a closer look of the IC with extract of the block diagram and pin out details, just for the sake of information:
The datasheet runs to around 44 pages with detailed information of the internal constructions and external connections required! I replaced the volume control with on/off switch (I am deliberately avoiding the use of ‘cum’ not to cause irritation to one of our eminent expert readers! (LOL) Lubricated the controls and switches and allowed the radio to work for several hours before fixing the back cover.
I did not replace the dead battery as it had only a very cheap replacement available in the market which would not even last for a few months. I informed the customer about it and he too said that it was not required. As it was not leaking or showed any tendency to leak, I left it there itself instead of removing it and finding ways for proper disposal. Here let us have a look at the broken volume control and the replacement made, to conclude this article:
For a change, no capacitors required replacement, I had to do retouch of a few dry solder joints though.
Mission accomplished and satisfaction of tiny nature got collected as usual!
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
December 13, 2025 at 8:35 pm
I tried to avoid reading the word that is a well known slang term for an activity I will not mention here which you deliberately tried to avoid but failed dear Parasuraman (lol). Although this potentially offensive explicit slang related term now may have attracted certain other readers.
The term "super senior citizen" was new to me, meaning a person that is 80 years or older. If it is a man he is now SuperMan (lol).
Parasuraman S
December 13, 2025 at 11:44 pm
Ha! Ha! I almost laughed my guts out! The pun was intended just for the sake of some fun, dear Albert! No offence meant! Yes, Super Senior Citizen means people of age of 80+. I think he was around 85! Definitely a Superman, as rightly put by you! Many thanks for your involved expert comments!
Philip
December 14, 2025 at 12:02 am
Thanks for the informative article, Engineer Parasuraman
Parasuraman S
December 14, 2025 at 8:44 am
Many thanks!
Mark J
December 14, 2025 at 9:11 am
Parasuraman great job. I always enjoy your radio repair articles.
Parasuraman S
December 14, 2025 at 3:30 pm
Many thanks, dear Mark!
Imoudu.O
December 15, 2025 at 4:42 am
I guess audio circuit is included in the single ic,thanks
Parasuraman S
December 15, 2025 at 8:07 pm
No, dear! There was an eight-pin audio amp IC. But all bands of radio were handled with a single chip IC.
MP
December 16, 2025 at 5:08 pm
In connectoin with what Imoudu asked, and in relation to the IC schematic, what possibly could the AOUT pin be for ?
Parasuraman S
December 18, 2025 at 8:27 pm
That is to be given as input to the amp ic.
MP
December 17, 2025 at 5:26 am
By any chance could the eight-pin audio amp IC you are referring to, be the 2822 IC. It made fault-finding a walk in the park. Vcc was oftenly a direct B+ feed to its power input pin (no regulator between). Speaker was also mostly, very simply linked to the 2822 IC pins. There was also the SMD version. They were easy to troubleshoot and easy to remove, just as they were easily available for easy replacement, for one to make easy money. What fantasy !
Parasuraman S
December 18, 2025 at 8:28 pm
Yes, I think it was 2822. Many thanks for your comments and inputs!
Yogesh Panchal
December 17, 2025 at 6:56 pm
Good Job! Sir
Parasuraman S
December 18, 2025 at 8:29 pm
Thanks, Yogesh Bai!