Teardown of Akash Tablet

Posted under DIY, Hacks, Repair, Teardown on December 18th, 2022 by

Found this old tablet lying around in our labs. It’s an old Akash tablet (2013 Model). It was designed and manufactured by the Indian company DataWind. It was a $50 tablet launched by the Indian Govt to provide low-cost tablets to students in order to increase access to educational resources and improve learning outcomes. IIT Bombay procured around 100k tablets for distribution across the country.

Coming to the internals and specs. It’s a capacitive 7-inch screen tablet with a front-facing VGA camera. The main processor is an Allwinner A13 SoC (ARM Cortex-A8 1GHz) which runs Android 4. It has a nifty Power Management IC in AXP209, which has 2 DC-DC converters and 5 adjustable LDOs and can support Lithium battery charging upto 1.8A. The I2C interface connects it to the main processor. The device supports WiFi connectivity with a prebuilt Realtek module, RTL8188CTV. It has a pair of 256MB RAM modules(256X8DDR3-WT, I think from HMD). This model seems to have a NAND Flash memory(MT29F32G08CBACA) of 32GB from Micron with a possibility of extending it to 64GB which remains unsoldered on PCB. SSD2532QN6 is the capacitive touch panel controller.

Well, the device is almost 10yrs old, I tried to turn it ON and it doesn’t turn ON without external power plugged in. Seems the battery is in deep discharge(2500mAh capacity) and the protection circuit is preventing charging it up even when I desoldered and tried to charge it separately. I have to remove the protection and bring it to a level then do the normal charge. There is no bulging or anything so I think the battery is fine but as always there is a risk with deeply discharged cells.

Overall the Akash project was an ambitious exercise but the hardware wasn’t upto the mark with a lot of complaints of overheating, boot crashes, software glitches, older specs etc. It never truly reached its potential of being a game-changer for students before the smartphone wave hit the country.

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Audio-Technica Headphone Teardown

Posted under Educational, Hacks, Repair, Teardown on October 2nd, 2022 by

One of my daily driver Audio Technica wired headphones was acting up. Opened it up and it was a simple fix. Nothing much to write home about. Found a loose wire which was fixed by adding a bit more solder and reattaching it. Works well now. The Internals of any wired headphones are mostly the same. They contain a driver/speaker on both ear lobes and are driven via extremely thin wires. The diameter of the driver here is 36mm. Nothing too fancy.

Now how do headphones actually work? The headphone dynamic driver consists of three major parts: A permanent magnet, a voice coil(electromagnet) and a diaphragm. When an audio signal(electric waveform) is fed into the voice coil, it gets attracted/repelled by the static magnetic field. These coils are usually glued onto a thin diaphragm which moves back and forth to displace the air. This creates the sound you hear from the headphones. This concept of a driver hasn’t changed in over 100 years. In the olden days, they used to have metallic diaphragms(Different from the plastic ones we have now) and strong electromagnets driven by the signal. The thicker diaphragms will need more power to move but the basic principle remains the same.

Headphones can have driver sizes from 20mm – 50mm. The driver sizes just mention the diameter of the static magnet. Marketing folks of companies have a field day trying to make you believe that the bigger driver diameter means better headphones. That’s not the case(Think earphones. They have driver sizes of 8mm-10mm). Bigger drivers mean that it can potentially displace more air. ie) It can produce more sound or can be louder. This doesn’t necessarily translate to an overall better quality sound. The sound quality of headphones is determined by the driver along with with the diaphragm quality and even the padding used in the headphones. It’s an overall system property. All of these determine the range of sound frequencies your headphone can faithfully reproduce in your ear.

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