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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Repair Tips for a Laptop

Posted under Hacks, Repair on December 4th, 2022 by

When ICs & PCBs became smaller and smaller, thermal management became a big deal in circuit design. It’s one aspect that heavily impacts the lifetime of the product you are designing. The reliability of a product drops in an inverse-squared fashion as temperature increases.

Last week my laptop was showing the classic Windows Blue screen of death intermittently. Initially, I thought it was a Windows software issue, but a bit of snooping around made me realise the processor cores were heating up. This is a common problem with laptops as it ages. What usually happens is that the thermal compound which is used to transfer heat from the processor to the heatsink dries up and its thermal resistance increases drastically.

Thermal resistance, as the name implies, is the amount of hindrance a part provides for heat dissipation. It is measured in Kelvin per Watt. What it means is that, for 1 Watt of power passing through the device, how much will that part heat up on the Kelvin scale. A larger number means it is pretty bad at conducting heat. All processors will be connected to a heatsink for heat management. These two are 2 solid surfaces that won’t have flush mating surfaces. The thermal compound is the key element that facilitates this gap-filling and helps in the efficient transfer of heat. In the PC build domain, there are tons of info online on which thermal compounds you must use, so I won’t go into details about that. In the end, it mostly boils down to a factor mentioned as thermal conductivity. Larger the conductivity, the better the heat transfer. It’s measured in Watts/Kelvin. When buying thermal compounds, pick the larger one in your budget.

Back to the laptop heating problem. Well, the solution to the problem is fairly simple. You need to dissemble the laptop and remove the heatsink. Thoroughly clean the old thermal paste with isopropyl alcohol, then apply the new thermal compound and put everything back. I saw all my CPU cores running at approx 10°C cooler after I changed the thermal compound and no more crashes. If you are having performance issues, this may be something you can try.

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