I'm attempting to build a small AM broadcast superhet transistor radio
from scratch and having a problem with the three IF stages oscillating
at the IF frequency (455KHz). The IF coils are salvaged from other
radios and the ground connections are to a common bus wire that
connects all the IF coil shields. It works reasonably well around 5
volts, but breaks into oscillation (at the IF frequency) if the supply
voltage is increased 1/2 volt and the signal drops off significantly if
the supply voltage is reduced 1/2 volt. So, it only works within a very
small supply voltage range of around 5 to 5.5 volts. The IF stages are
decoupled from the supply with a small resistor in series and bypass
cap to ground which helps, but doesn't solve the problem. I'm wondering
what can be done to stop oscillations and increase gain?

How did they manage to avoid the oscillation problems in the old tube
radios that were hand wired without any PC board?

-Bill