Vintage Pocket Radio Transistor Replacement is Oscillating
Hotter transistors can cause problems .There are cures that can be tried .You can remove the neutralisation caps on the IF stages .These caps were used to compensate for the CB capacitance which was higher in older transistors .Modern AM sets do not need these small caps due to better transistors .You should also check and replace any suspect bypass caps like the one on the AGC line .        Now you can place damping resistors across the full primary of the IFTs to reduce gain and selectivity .Start at 47K going down until the set stops squealing .Bad cases may want 10K .An alternative to damping resistors is to place some unbypassed emitter resistance  like 33ohm in the offending transistor .These tricks worked for me in the early 1970s in the absence of good test gear .