Unstable HW

Hardware Mods For the MK808.
Hemiyoda
Posts: 4
Joined: Sat Dec 22, 2012 5:47 pm

Unstable HW

Postby Hemiyoda » Sat Dec 22, 2012 7:23 pm

Hello,

My MK808 worked like a charm for 4days (maybe 8hours total run time) but then it started to act up. Did the usual as others have done, i.e. new powersupply (eventhough I got a 2A unit), flashed the device to newer firmware. No go, still bombs (freezes) after 5-10minutes.

So I disassembled the device, looking for bad solders with a microscope, badly placed components etc. I even x-rayed the BGA:s ( I work for an EMS, we manufacture industrial electronics ). All looks good. (not perfect, but should work). The device doesn't really get hot, maybe 35-40C. I see 0-7W on a 230V watt-meter. I experimented a bit with freeze spray, it does indeed work stable if I cool it with freeze spray. Why did it work perfectly without tricks the first 8hours?

I find the RK3066 datasheet brief. Find some recommended operation conditions (voltages). I start probing the outputs of the buck regulators (4 in total ( marked AB2QN )).
I can't find the Internal Digital Logic 1V to max 1.2V. The lowest voltages I find are 1.38V and 1.40V.
- Have I measured in the right spots?
- Has the device been built with wrong resistor values in the feedback network for the regulators resulting in ~1.4V which has slowly led to its destruction?
I have changed the values of the feedback resistors so I have 1.2V now but it is still unstable.. Guess the CPU is toast now if the core voltage has been cranked to 1.4V..

Pictures attached for the ones interested.

//Hemiyoda
MK808_1.1_1026.jpg

recommendopcondRK3066.png
You do not have the required permissions to view the files attached to this post.

Hemiyoda
Posts: 4
Joined: Sat Dec 22, 2012 5:47 pm

Re: Unstable HW

Postby Hemiyoda » Sun Dec 23, 2012 10:32 am

Another picture. I have removed (and substituted w/94kohm) 1 of the 2 FB/ADJ resistors on both regs. Mine were 130kohm. ( Still unstable though ) Wish I could run memtest86 on this thing. :)
You do not have the required permissions to view the files attached to this post.

marblema
Posts: 4
Joined: Mon Jan 21, 2013 5:03 am

Re: Unstable HW

Postby marblema » Thu Feb 28, 2013 5:16 am

Did you try a better heatsink as you mentioned it will be stable if you cool it down?

And maybe you can ssh to the underlying Linux to check OS logs, like dmesg?

--Marble

1branchonthevine
Posts: 4
Joined: Thu Dec 20, 2012 12:20 pm

Re: Unstable HW

Postby 1branchonthevine » Tue Apr 02, 2013 4:19 pm

You sound like an Android guy, try this with your phone too! Download "current widget" from google play, then compare how much current your phone is using with each of the chargers you have lying around the house. I have a 2.1A charger for my phone, and when I compare the current draw between it and the OEM HTC 1A charger, they both still only put out 680mA! Then I tried some cheap cables I bough off ebay, and I got only 60-200mA! Likely the cable is the culprit. Also, the longer the cable, the noisier. Look for a high current, ferrite core filtered cable, and this should do the trick. I have yet to find one, so maybe make it yourself with a cable and connector kit. Good luck!

ayaan
Posts: 16
Joined: Wed Mar 27, 2013 2:57 pm

Re: Unstable HW

Postby ayaan » Thu Apr 04, 2013 2:08 am

Perhaps the contact between the heatsink and the CPU is not so good. Heatsink should be much hotter than 35-40C, IMHO. Maybe heatsink not too hot, but the processor is overheating, because the lack of heat transfer. IMHO, as an offer.

You should look at the heatsink and processor connection. It can be seen from the side. On one of my devices heatsink skewed and with the gap between the processor and heatsink. I have no experience removing the heatsink, so, I made ​​a holes for better cooling. The device does not stop now.
two MK808 in use


Return to “Hardware Mods”

Who is online

Users browsing this forum: No registered users and 1 guest