Hi all,
After a lot of connectivity testing, de-soldering, resoldering I got my A4000D back to booting with full AGA. The intial non-boot I reckon was down to a knackered Buster. I replaced the Rev 09 on the board with a Rev 07 one from my A3000T. Machine booted but no AGA. 16 colours only. I ordered a Buster 11 and installed A4000D booting happily into WB but still no AGG. Amiga TestKit reported "WARNING: AGA Alice with bad Lisa ID".
Lots of googling later I narrowed possible cause down to U976 by following "Chucky" A4000D repair guide. I ordered replacement parts for U975, U976 and U177 plus some 4.7K resistors and some new ceramic capacitors.
Lots of youtube later I de-soldered U976. Checked connectivity - the vias under the chip. Hmm not all good. Long story short after checking all connectivity from U976 and repairing broken traces on the top-side and the bottom-side, replacing a resistor and a cap along with U976 Ive got it working with AGA. its been almost 10 years' since this machine worked and I thought it was gone for good.
Wife will be happy too as she can now get the kitchen table back!
Weed