Originally Posted by koimr
You should re-read the posts in question; no one was claiming that our units should function on 9 volts and @DWilks even said it was the cause of his problem (he didn't do it deliberately).
He passed this information onto the forum and I thought it was a useful tidbit. I really don't know where you are trying to go with your response above, it's already been decided the 9 volts was a mistake.
You are exactly right! I only offered the info in case someone else had problems with their sound not working. I'm running off a car battery in-house to test different apks and especially sound apks and gps navigation. This is much easier than sitting in a hot car fighting the heat and bright sun light! The specs on the particular audio amp in my JY head unit list supply voltage as 14.4 volts +or-
10%. So 12.96 volts would be the minimum voltage according to specs. Since I'm not connected to a vehicle charging system, my battery voltage has gradually lowered past the operating level of 1 or more components inside my head unit.
That's to be expected.
NOW! for a new problem that someone else has mentioned: The Volume Control,
my unit has the physical pwr/vol knob, stopped working and also the volume window that should pop up no longer did. To get the volume control back working, I had to reboot the unit and all was back to normal. A voltage check at the time showed 12.3 volts from the battery. My volume still worked, but I could not change it either up or down. Neither problem was fixed by powering off or applying the correct voltage. That took a reboot with the correct supply voltage.
This post and the one about the sound not working is just information posted for others to see that the battery state is crucial to the correct operation of these radio/navigation units! So, if your unit starts acting strange, it might behoove one to suspect a voltage supply problem and not apks nor mcu's nor roms! That's 2 problems that someone else has mentioned duplicated on my unit with battery voltage below levels that the unit needs. Hope this helps others....your problems may vary but do suspect battery supply voltage especially if your vehicle is not actually running when the weird problems occur or if you've just started your vehicle like in the morning or a long time in between running........