[MTCB Android Head Units Q&A] kaween:
Hi there !

3.8Ohm should not be the reason for breaking the AMP chip. At 2 Ohm, I'd become slightly worried, especially if it would be common rule that most of these RK units have little to no cooling for their internals, and the cooling of the amp chip itself is totally substandard (at leasty on my JY unit).

I do not say this lightly. On ALL android units I've used and tested so far, the backplate of the unit is used as a heatsink for the AMP chip, sometimes even for the internal electronics. And at least the JY I've got here comes with a backplate that "floats away at the lightest breeze" : the more massive the rear heatsink is, the more heat it can actually dissipate. Compared to the heatsinks of the AN21-U or the S150 series, the heatsink of the JY is a joke : the backplate of a typical AN21-U weights about as much as the complete JY unit weights !!

There's NO internal cooling at all in the JY, no air flow, no heat dissipation on the cpu ... it is really a very low-cost design in terms of used material. Again : I like the RK, but in terms of build quality, it's bottom of the barrel. I would not be surprised that lack of heat dissipation of the back of the unit is directly connected to the death of your original Amp chip.

On my unit, I've added a near-silent 12V internal fan : there are enough little holes and ports in the housing of the JY to force an airflow without cutting parts of the units housing. When I measured the surface temperature of the RK3188 chip after 20 minutes, it came back at 61°C, and that's running outside of the car, on my electronics testbench. What kind of temperature this chip would run in a summer-hot car ... can't say, but I promise you it will be a LOT higher. Acoording to specs, the RK3188 has a maximum operating temp of 85°C. I would not surprised that in high temperature enviroments and build in a dashboard which will exclude the possibility for natural heat dissipation, the temperature will reach that value quite easily.

So I installed that fan, which blows an airflow over the SOM board and hits the AMP chip head-on. On my testbench, the heat on the cpu chip goes down to 27°C afterward (JK thermocouple stuck to the cpu's surface).

Why NEAR-silent ? Because I WANT to hear it running if I need to without opening the unit. I could've used a totally silent fan too, but if the unit would fail because of a dead fan because I could not HEAR the fact the internal fan had died .... that would be stupid and yes, it has happened to me. :)

When using the same external amp as I did : a word of warning. The RK JY at least does have an external amp control line, but here -again- the cheap design of the JY is seen in the fact that when the unit is off, this control line is NOT forced to the ground level (0V) but it simply "floats". Meaning : the amp I used needs a control line that forces the remote line to really be pushed to 0V by the headunit; The JY can NOT do that. It will go nicely to 12V when "on" (normale) but "floats" at "off". The amp's remote line itself floats TOO by design : the idea is that you can run the Amp also if you do not have a remote-line control for what reason ever.

As a result, the JY was NOT able to shut down the external amp when the JY is switched off !!

I solved this by using a micro-relais that is commanded by the said Amp control wire of the headunit : at "off", the NC-line of the relais forces the remote line of the amp to Ground level, when switched on, the remote line of the amp is connected to the 12V line. Like that, everything works correctly.

For the people thinking I'm dishing the RK/JY : I'm not. In terms of price, it's a really nice unit, and with the great people (not going to name anyone as I would certainly forget to mention people who rightly deserved to be mentioned) that have and still are supporting/developping software to make this unit work far better than is possible compared to the out-of-box situation, it is probably the best unit for the money you can buy today if you don't mind experimenting a bit. But honestly : without the support of all these people, I would not be able to recommend these units as out-of-the-box, there are quality-wise better and more complete units available for a comparable price.

But in terms of build quality, the unit I have here (JY) is only so-and-so, and it does need a bit of TLC to make it ready for prime-time, at least in my humble opinion.