OS 9 does not start.

[IIO]

capacitors can also die from a machine not beeing used for years. :/

[gert79]

Another thought, i saw that original Apple parallel cable has this notched out wire, probably for master/slave cable select.

I am using a normal 80 conductor pata cable without this notch, can this be an issue that the drive is not recognized?

[robespierre]

The bus addressing scheme in ATA has confused users for as long as it has existed.

See this summary:

2. After each Reset, the "Slave" asserts a signal (DASP) briefly to tell the "Master" to wait for a second signal (PDIAG) before reporting status to the PC. PDIAG is set when the "Slave" completes diagnostics. This somewhat bizarre process is a concession to making software originally designed to work with MFM disk controllers think there is only one controller on the channel rather than two. Apparently, almost all IDE setup problems are due to mishandling of the DASP and/or PDIAG during drive initialization.

The cut wire shown above corresponds to PDIAG. What this appears to mean is that the cable was modified to prevent the behavior described above: of the "master" drive waiting for a signal from the "slave" drive before it will try to communicate with the host.

Your symptom of the machine not being able to boot when reset is consistent with this: if the drive is waiting for a signal from a "slave" that will never come, it won't ever report its own existence to the host, and without a drive the system will never start.

[gert79]

I finally managed to get it running, reset works and machine runs stable after every boot!

The installed PATA cable was already very wavy and bent a lot, that's how I got it from previous owner. So I replaced that cable with one in better shape and my issues are gone.

Probably there was a bad contact on one of the lines, I have no other explanation.

[GaryN]

I recall my first guess was the ATA adapter. The cable would have been the second.
Everybody just took the long way around to get there.

OCCAM'S razor.