Assuming:
1 You cleaned the heads really well
2: You didn't remove grounding screws (bad grounding= snowy pictures)
3: Ribbon cables are well seated in their sockets for the AC head and Drum/preamp (check again please),all the way down
It could be:
1- Tape tension issue (back tension arm) (check with your finger on the left side of the tape path if the tension if good (not loose),same thing on the right side
2- Can be an issue with the Post guides (P2,P3) that need a tweak
3- Check / adjust your AC head
The AC head is a set of two heads: one for audio linear a.k.a mono (reading & recording) one for control track (tape speed infos reading SP/LP, and Sync pulses i believe)
If not set properly it certainly can affect the quality of audio
and also video to the point it's snowy and audio is muffled.
Adjusting it will not be easy without a scope but it can be done good enough (i did it on my philips, and some other vcrs)
two videos for you:
Adjust the AC head:
https://www.youtube.com/watch?v=fazLIPQqKLk
back tension (~8min mark):
https://www.youtube.com/watch?v=1dY0...Vuc2lvbiB0YXBl