I have a rocketfish rf-hv3 mobile ipod dock thing which works quite nicely, runs off 4 AA's or a wall-wart and has quite nice sound quality for 2 little speakers. Issue is if no signal is recieved from the line-in or ipod dock after 5 minutes then the device will automatically shutdown. This is a problem because when I first got it I planned to use my iTouch as an alarm and charge the itouch at night but after 5 minutes it would turn off and when my iTouch started going off it wouldn't play any music to wake me up. Also its an issue when I use the line-in to connect it to my Yaesu HT and after 5 minutes of silence on the repeater it shuts off and then when something does come trough I never hear it...
Well after messing around with my little digital osc. (DSO Nano v2) on the dock, I noticed the N79E825 MCU which runs the dock has the (left?) mono signal going to pin 16 which is the P0.5/CMPREF/AD2 pin. Well with some trial and error I've noticed if that pin stays low for 5 minutes then it turns off regardless if theres a signal going through (Tested by using jumpers on the IR GND and the P05 trace already cut for programming on the left side of the chip, fed the radio through it and it still turned off while getting a signal).
My fix for it? Well its quite simple, I originally was going to shove a 555 timer in it to make a inaudible signal on the P0.5 but turns out that pin has no effect on the actual output to the speakers so you can give the pin whatever. Lucky for us the VDD is the pin right above the P0.5 so you can solder those two pins directly together and viola, auto-standby disabled :D
This is my first little /hack/ on a proprietary thing that I actually have a use for, feels good. Now I can wakeup to some Tune-In radio on my iTouch instead of some crappy radio station at 5 am. Also don't miss any QST's on Skywarn that come through my HT expecially during tornado season.
Hopefully I'm not the only one that finds a use for this, I saw a best-buy review mentioning the auto-standby feature but no others.
Thanks for reading.