A miracle cure

[9aplus]

Kicking, knocking, heating, etc...
are almost normal search steps for cold solder joints....

Have recent experience on that for similar aged (mid 1980ties) technology.
One on my Sony ICF 2001D developed strange symptoms after cleaning some
"computer" 3V battery leak. The unit mimic blocked bands with all jumpers set
on all bands open. That influenced AIR band, FM band and HF band over 26.1 MHz.
That unit have 3V (2 x AA size) and 4.5V (3 x D size) power.

Lot of knocking and than heating on 100 C located the trouble
around two IC one shifter and one 4 bit CPU.

Finally cleaning and re-soldering of both IC resolved the trouble.
Here demo on finished unit, the right one, with clean white keyboard keys
=> https://youtu.be/2j6ofUqw6ww