The Y sus heat sink is cold because this board is not working.
The 187 and 60V are all right, this tells me that the Y sus was shorted (this was the reason for having the fuse open) but when you replaced the fuse- the new fuse did not open up anymore, but something else on the board opened up, removing the short on the VS line.
The Y sustain board is defective and it will need to be replaced.
The part# XXXXX this Y sus board is:
The best price I could find for you for it is here:
This is a very common issue with these sets, and most of the time is the only failure inside the set.
I believe that replacing this Y sus board will fix your problem.
The Y buffer can also be defective, but because this open fuse on VS that you had is unlikely..
Please accept my answer if you are satisfied and will be able to leave a positive feedback.
Thank you, XXXXX XXXXX a great day!