Final report on now working 6128.

[Bignumbas]

Started with a blank screen on power up.
Ram and CRT chip brought me to ready prompt with phantom key input and insert cassette on typing Run"
Slow boat from China arrived with AY soundchips.
Replacing this fixed phantom keyboard input at startup.
Then I was getting no ready prompt.
Tested the 40015 rom and found it to be faulty.
Still no prompt.
Remembering my French 6128 I decided to socket the FDC 'cause when I touched pin 2 it would go to the ready prompt.
Still not working after inserting good FDC.
Piggy backed the 74HC240 with a good chip and all good so replaced that with new chip
Next time I will check the 74 chip first but I have found with fault finding that you always start at the wrong end.
6128 mainboard is back to full working condition 

Finally tally of repairs:
All ram replaced
IC108 - CRT chip
IC102 - AY sound chip
IC204 - 40015 Rom
IC203 - 74HC240
plus I had to repair 3 broken tracks caused by desoldering 412 chip legs.


PS: FYI  I stupidly inserted the FDC chip in reverse. Why did I do this??  No boot at all and saw a wisp of smoke.
  Tried again with a good FDC and all worked. After letting the red hot FDC chip cool down put it back in correctly and it is still working.
Phew!! That saved an order to Israel for a new FDC.