GTO RB570 Transformers / Mighty Mule RB570 Replacement Transformers. GTO PRO RB570 Transformer - 18 Volt/40VA - SW2000/3000/4000-SL1000/2000 UL ONLY. Use this transformer for the PRO3000, PRO4000, PRO2500, PRO1500 as well as the Mighty Mule FM500/502 andGTO RB570 Transformers / Mighty Mule RB570 Replacement Transformers. GTO PRO RB570 Transformer - 18 Volt/40VA - SW2000/3000/4000-SL1000/2000 UL ONLY. Use this transformer for the PRO3000, PRO4000, PRO2500, PRO1500 as well as the Mighty Mule FM500/502 and