The Stereo Tech said it was a bad Tuner I.F. Chip or R.F. Chip in 2013.
That receiver is late 70s. The chance of the chip in question still being available from the original chip manufacturer is remote.
However there are a number of firms who snap up the ends of lots and "hoard" them.
So one would need to know what the chip is you need and if one can be located.
I should warn you that these firms usually want a king's ransom for unavailable chips.
If the chip can not be sourced, which is the most likely outcome, given the age, then the unit is not repairable.
The arrival of the chip age has made vintage restoration highly problematic.
My guess is, that it is the phase locked loop IC that has failed. That is the date about when PLL ICs started to be used in FM radios and receivers. They improved the performance greatly.
Absent a replacement IC the unit is not fixable.
Another factor to consider, is that due to age the replacement may not work either. The sellers do not normally provide a refund. This chips are strictly as is, as was.
