CPC664 Initialisation issue.

[SerErris]

If you want to understand if the FDC is the problem - desolder it (or at least the Power PIN) and check if that solves your issue.

[kolleykibber]

FIXED IT!

So after deep cleaning and reflowing the joints around the disk address logic, I had no luck. Then I thought i'd trace the pins back again from the IC207 OR gate into the flip flop. this was going momentarily low and causing the flipflop to set ROMDIS high. It was barely noticeable on the scope. Tracing the momentary low, led back to IORQ on the Z80. The only socketed chip I hadn't tested yet.  arrgh.  

So in the end it was just the z80, which seemed functional in every other aspect. FDC was detected fine and no more strange warmups.

So lesson learned, do the simple things!

Have to say I enjoyed the challenge. Now I need something to do with all the gear arriving from china.

[Rabs]

Well done. So you had to replace the Z80?

[kolleykibber]

Yes, I swapped the z80 from a 464 and all was good. Well, apart from the keyboard membrane. Although, one plus is the drive still seems to have an intact belt.

Thank you and everybody for the help. It was very much appreciated.

Now where does one get a reliable z80 from?