Anto, the good news is that Quad gear is infinitely rebuildable. My Quad valve amps go back sixty, seventy years, and my newest silicon Quad is probably the CD player. I have and still use a 3 series preamp, and when I wrote on music, my backup amp for 15 years was a Quad 405 MkII which has lost count of the number of times it has been rebuilt. The trickiest thing is replacing the cables when accidents happen to the connection. Jones HV connectors, anyone? They're those rectangular plugs with flat blades that connect the Quad II units together.