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Reviving dead SX-680

It might be good to double-check the lead orientation for Q7/Q8. The 680 uses a somewhat unique muting scheme, and due to that C121/C122 and R120 should be checked for value, and C122 for polarity.
 
double checked on Q7/Q8 pin-out. R120 100K checked. Replaced C122 4.7uF/50v. Not check on the Ceramic C121 though. Took few voltage reading on P3001A Pin1, 2, 3 all were about 1.9v instead of 2.1v. pin 6 were actually 5.6v.
What weirdly is when hook onto pin1, while the switch to FM and muting is off I can hear a fix AM station, with lots of static, regardless of where the dial is on. On other 3 pins, I can hear different weak FM stations.
 
I think the problem must be at the front-end FM. I put a spare HA1125 in place of the PA3001A and make no difference, weak statics FM stations. I don't have equipment nor experience to do FM tuner adjustment so I will have to put this receiver aside again.
 
Back at this last night, as yesterday I got a freebee SX-580, with dead channel, with good FM Stereo reception.
After review the schematic, I am sure that the front end boards are the same. So I (painfully) move the 580 front-end to the sx-680. Same problem as before, so it's not the front-end.
I believe I may have a ground problem somewhere. When in FM mode, with muting/stereo is on, it hum/buzz when I touch/close to the volume and balance bare pot (i.e. no knobs) . Couldn't tell when in AM nor FM muting/stereo is off, as it produce static noises. Will take note on other functions later. How do I check for grounding problem, beside visual inspection? Could the function switch or the pots be the problem?
 
:banana:! I did it! replace the 4 0.047uF ceramic capacitor around the PA3001 C118, C119 , C121 and C123, FM is on even in Stereo.:banana: Should have listen to Watthour few post earlier. Nothing to do but, button this unit up...
 
2 birds in one day. This time while prepare to button up the 680, since the 580 need to re-solder back the swapped tuner, may as well clean it & replace those noisy transistors and investigate the SK0029 modules for dead channel. Swap them around the problem switched. So another dead SK0029. Don't have one, but have a spare SK0039 from the 680. Put it in place of the dead SK0029. It worked! I thinks I will recap this one as well. Do you think there would be some problem if I keep the mix-match SK0029 and SK0039 pair in this 580?
 
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