The 12 V for tuner comes from Q4106 12 V regulator
Voltages on it should be +- apx
Col 18V
Base 13.4
Em 12.7
You may want to measure the bandswitch / tuning voltage IC.
It is U3600
Also see if either Q4106 or U3600 get hot after a few minutes.
Should be just warm.
73 Zeno
LFOD !