Cs90x recording issue

[hghareeb]

Hi,

I noticed a recording quality drop when i do recording for long time, the first 10-20 minutes sounds good after some time if recording the vocal and music sound will start to a kind of vibration or not holding consistency in tone, well I don’t know how to describe it but almost like vibration in tones, I tried to replace the power supply as i have a used spare one with no luck, also i tried to change the belt , I also replaced the motor but with used one so am not certainly sure if it is the motor or not.
Is there any other thing i should start with, something that could be getting hot after sometime of recording?
Regards

 

[Superduper]

Possibly a pinch or idler

 

[hghareeb]

Pinch roller already replaced with new, then possibly idler ,, forgive my ignorance but where is the idler located, mine has a belt to run and transfer the movement from the motor to the flywheel. Could it be right behind the cassette located?