Don't Pay high service or Diagnostic Fees, Toptech charges a $60 Dollar Diagnostic Fee only when repair Estimates are not Agreed upon. All work and parts are itemized prior to starting the job. Toptech Engineering Service, offers quality and comprehasive diagnostics to the High End appliance industry. : We do not offer phone Estimates. : We Don't Sell Parts. Toptech Engineering offers service and repairs for all your High End appliances. Toptech is factory authorized for Major brands like Marvel, Aga, Northland, Summit, and ULine we also service Sub Zero, Viking, Miele, Thermador, Bosch and many others. Toptech Engineering provides service for, Home Warranty of America and, Aig service warranty and. Service Power, These companies offer extended warranty to all major appliance retailers such as Loews, Home Depot and others.