My M421 was working fine last January and now after charging up the boat battery (12.9V), it appears almost dead. As power is turned on there's a tiny crackle- similar to the radio normal power up sound only quieter - but thereafter no display, sounds or function. I've checked the power leads and now taken it out and put it on to a different battery to ensure it's not resistance in the leads or a dud battery. Nothing doing but it's definitely drawing current.
The unit is about 5 years old and I know it was working as I was listening out for the weather forecast as I cleaned the boat prior to covering it. The radio was left switched on since then
. (note passive third party)
I can't see how its draining down the battery could have killed the ICOM but it was working until that 'incident'.
I've emailed ICOM UK with the details to see if they're any help but any suggestions or details of similar experience welcome as it's unlikely to be worth repairing but more importantly I'd be concerned if it was that easy to kill an ICOM or any other radio.