Just an update... after 52 days, the parcel with the Game Boy Advance front light kit arrived!
Normally, from China to Italy it takes 30-40 days, in these times, kudos to the international mail services!
First thing, the acrylic light guide panel fits perfectly the QY100 display.
Next steps:
test for frontlight placement: the frontlight panel by design is more illuminated near the LED strip, I think to place that at display bottom, since is the most "crowded" zone (pattern names, "grid" display, mixers, etc..);
I'm eyeballing the schemes on QY100 Service Manual to find a good spot where to solder the two LED wires: I'll test tapping form the HOST SELECT switch, since it is of scarce use and when in "MIDI" position (i.e. its normal position) there is a not connected pin that is driven to ground via a 10K resistor: almost perfect, just need to find a +3.3V (nearby pin on same switch): soldering on IC33 (3.3V regulator) should be the simplest option.
Any other ideas are welcome on i) where to tap 3.3V and (optionally) ii) using something different to the micro (tiny indeed!) switch present in the kit, intended to be placed in the battery compartment.
Mote to come... with photos, if needed.
prea