Regarding schematics or service manual:
Contact Digitech for these - they will charge for it.
I usually can find schematics and/or service manuals, but some products have always eluded me, like the Digitech TSR24S - for obvious reasons, as this one was close to an Eventide 7000, and, as Digitech was bought up by Harman Kardon, who also owns Eventide, they want anything about the TSR24S gone from the net
I haven't been able to locate schematics or service manual for the GFX-1, so...
However, I did find it for the 2120 on elektrotanya, using this query:
site:elektrotanya.com
product schematics
or
site:elektrotanya.com
product service manual
Best of lück