I have a Kenwood TH-F7E handheld transceiver, bought second-hand a bit less than a year ago. Until about 3 weeks ago, it worked perfectly, then I put it in a drawer and didn't touch it until yesterday, when I noticed that it didn't switch on on battery power, and the charge light didn't come on when plugged in. Here's what I've found out so far:
I measured the voltage between the battery terminals as 0 volts, so my first thought was the battery had simply gone bad. The battery is a PB-42L Li-Ion pack.
However, there are also some signs of a problem with the transceiver. When the mains adapter is plugged in, the receiver seems to work normally, but the device heats up a lot after a couple of minutes. This happens even if I remove the battery pack.
With the mains adapter plugged it, I can transmit with extra-low (0.5 W) or low (2 W) power. In the high-power setting (5 W), the transceiver restarts as soon as I hit PTT.
I tried connecting a 7 V power supply directly to the battery terminals of the transceiver and noticed that it draws 900 mA even while turned off. I immediately disconnected the power again, without any testing, when I noticed that.
I've found the service manual and was planning to open it up to figure out what exactly is producing the excess heat and make some measurements, but I was hoping to get some advice on how to troubleshoot this before I start digging around in the transceiver.