First welcome to the site.
This sounds like a known issue with the radio in question.
Have a good look at the PLL board. It is the smaller board sitting in the can that is attached to the chassis on one side.
You will need to unplug this board and remove it from the mount. Look closely for weak solder joints. They are there.
Also look for Sony Bond glue. This is a beige color glue that was used to hold parts down. It has probably turned dark brown by now.
This stuff is very conductive and causes shorts.
I understand what you said about the capacitors. But to be really sure you have to remove them and see if they leaked onto the board.
You can get the service manual here:
http://www.cbradio.nl/realistic/Service_Manual_Realistic_HTX100_Homer_ENG.pdfLet us know what you find.
Buddy