Respected Prof. Mujumdar,
Actually the working circuit diagram of the SMPS of Ragini Digital Tanpura is not available.
The Ragini designers have changed the circuit almost 13 times within last 2 years.
So I don’t know if at all the circuit will be any of use to you…
Since your tanpura is working on 12V adapter, I will suggest you to continue with it as much as possible.
Because the company has such a monopoly in the product that they change the thing quite randomly that you can not continue with its pace.
Rest assured, please continue with your beautiful modification.
I will also include your modification details in my next article on Ragini Digital Tanpura on my website.

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Actually we have offices in Mumbai, and also in other cities. But we operate all other branches only during summer vacations.
Currently we are the natives of Nagpur, currently operating at Akola.
Hope my advice will be beneficial to you…!
All the best…!
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Dr Vidyasagar Ji thank for replying
In my case Ragini digital tanpura having soft touch button to increase and decrease the volume and for power it have separate soft touch button when power on the tanpura initial only we can hear a very very low click noise from speaker for friction of second there after no sound and wher powering off the same click sound come from speaker for friction of second so please guide on this problem for this model
Thanks and regards
Sunil Amin
7028474734

The solution to your problem is quite simple.
Open the lid of the tanpura and remove the variable resistor which works as volume and on/off button.
Connect DMM in Ohm mode, across any two adjacent terminals of variable resistor.
Now rotate the variable resistor, you will see that its resistance does not vary smoothly.
Check the value of the variable resistor at its back side.
Purchase new one and connect it inside the tanpura.

Is your problem solved with my suggestions? Please share your experience!

I have already tried with a couple of Ragini Digital tanpura to break the filler material around the microcontroller circuit inside the Tanpura. I also tried it with two types of mild acids H2SO4 and HCl.
I did it as follows, but cannot guarantee that it will surely work.
1. First I disconnected the microcontroller circuit from the main board.
2. Then I dipped that block into dilute HCl for one night i.e. about 12 hours.
3. During next morning, I took it out, wiped with moist cloth.
4. Then using a ball pen hammer, I mildly hit the stone like block, it cracked and then slowly and patiently I was able to remove the cover.
5. But to my surprise, the microcontroller board is pre programmed.
6. And since we don’t have its program, I tried different combinations with my programming skill, but no luck.
So if you have patience enough, try it, else, leave it – this is my genuine and experienced suggestion.
Now a days, the such instruments are not repairable. They are use and throw type.

IF you are listening to hissing sound only, there are two possible symptoms.
1. The volume control button is faulty, replace it.
2. EPROM is not generating the preprogrammed swara sounds.

Yes. 21.46V is very high voltage. Actually the circuit runs only on 9V maximum.

Sure.
Wish you all the best…!
But I think that will be a waste of time.
But you can try it for yourself.
Awaiting eagerly for any positive result.

Sorry! The EPROM R -616-532-220 is manufactured and programmed by Ragini Digital company itself and its technical details are the sole discretion of the company. I already, many times, tried to contact them regarding this and they said that they don’t provide any spare parts of their instruments.
So the only thing, that you can do is to purchase a new instrument and forget this one…!
What else can I say! I, myself, thrown away about 4 such instruments and suggested my clients to purchase new one!

As per the symptoms you are explaining, I think that there must be some internal problem related to the sealed circuit that is the EPROM circuit of the device.
If it is really related to EPROM, then we can’t do anything at all since that part of the entire circuit is sealed and cannot be repaired.
I actually never worked on that section of the device. Sorry!