This morning it occurred to me my car almost didn’t start. The battery seemed almost dead. It couldn’t be the battery itself since it is about a year old. When I was thinking about it, I did noticed a low voltage in my battery before. It had to be standby problems with some device in the car. Today I pulled one of the battery leads and put an ampere meter in between.
I use the radio in the car mainly for APRS and some chatting on our international repeater PI2NOS. Clicking off the contact, there was stil running about 2 amps! The only thing that has it’s direct connection to the battery is the TM-D710. I pulled the display plug from the TM-D710, the current was still flowing. When I pulled the plug on the main unit, the current was gone. Connecting the main unit, no current. When I put the radio on with the display and turned it off again, there was the 2 amps of current again.
APRS drains battery
The other day I forgot to turn off the Kenwood and it runned APRS for a whole weekend at full power. On monday my battery was completely drained. But that didn’t surprised me at all. But when I switch off, I expect the radio to drain no current at all.
So it seems like there is something hanging in the TM-D710 main unit which prevents it from shutting down. Also there must be. something wrong as 2 amps of current in standby modus is way to high. Even in receiving modus the TM-D710 should use that much current. I will disconnect the rig from the car for now and take it to the club on Thursday. I hope I can find what is wrong with it.
If you havent sorted it out yet, the 710 never actually shuts off. The 0/1 power button on the front panel doesn’t actually control power. When pressed, it sends a logic low to a pin on the display processor. The processor detects the change in state. If the the radio is “off”, it now turns on. If the radio is “on” it now turns off. What it is actually doing is putting the processor into a “sleep”/standby mode (radio off), or waking it up. As long as there is power to the radio, most of the radio is still active. This is, in part, to to keep the memory circuits alive. There is an onboard 3v battery for the memory, but the battery only lasts for a few weeks, when the radio is unplugged. The off mode of the radio turns off some voltage regulators when the processor goes to sleep, thereby turning off portions of the radio. Still, a 2 amp drain is quite a bit, even for a sleeping radio. One of the regulators that is turned off is the 8v bias used for the RF circuits, which should kill the transmitter.
Im currently chasing a problem with a ‘710 where the radio seems to autonomously go to sleep (“off”) after about 1 minute. Mine requires a hard power cycle to bring it back to life for another minute.