GTA02A5 Boot without battery
The GTA02A6 boots without battery (at least using NOR), but the GTA02A5 does not. The reason is that C1767 was changed in A6. Here are some hints for replacing it: C1767 is only sized 0805 or 0603 on A5, so you have to add another cap in parallel. Fortunately there is a bit of empty space on the pcb near C1764. I have taken 587-1963-1-ND CAP CER 100UF 6.3V X5R 1206 from digikey. One side of the new cap goes to the GND side of c1706 and you have to take care not to touch c1729 and tp1704 the other side of the cap ends in the middle of c1764 (which was rotated by 90 degrees between A5 and A6. and is connected using a short wire to R1767.
Keep care that the isolation strip is still over the various 1206 sized pieces.
The picture shows the place and wire to the new C1767 in red, the old C1767 is marked in magenta