Atari 1040STf troubleshooting

[Calgacus]

Hi Guys

I have Atari 1040 STf thats not working

It was given to me by a neighbor who was moving house. The ST shows the Power LED when turned on but no other signs of life. The floppy LED does not come on with or without a disk in the drive.
I have tried a known good ST power supply and a known good Floppy drive with the same symptoms. Unplugging the keyboard does not produce the constant beeping noise either.
At the moment i don't have the correct monitor cable to see what display output its giving
The motherboard looks clean and i believe it has never been opened before i got it.There does not look to be any swollen,leaking caps and all socketed chips have been reseated by myself

I have ordered a replacement shifter chip and monitor cable, is there any other test i should be doing to try narrow down the issue.

Any advise appreciated

Thanks

[rubber_jonnie]

Before you do anything else I'd wait for the monitor cable to arrive and see what's happening on screen.