found a seller doing MXR Phase 100 circuit boards minus vactrols on eBay. Might have been able to fit it in a 1590B, but I went for a 125B! : r/diypedals
Vintage MXR Phase 100 Restoration & Modding – Joseph Sprint
Pedal de velocidad PH-12 MXR Phase 100 con efecto personalizado, controles de Bypass, pedal de efecto guitarra eléctrica con conector de Pedal dorado Biyang _ - AliExpress Mobile