B&W MPA1

One off my blocks got a damage. The headfuser collapses when you put it on the power network. Any suggestions??
And has someone a single block for sale??

Well, such power amplifiers can usually be repaired. They are not quite new anymore, so some parts may be hard to find. I would consult with a qualified technician because you seem to have a short-circuit somewhere.

They're a fairly simple design and all components are still available, though the power FETs are getting scarce (There's two different types of MPA1 - UK & Japanese built which have different FETs. I have some stocks of both types) Weak points are the bias transistor which tends to run hot, and if it fails open drives both sets of FETs full on, effectively shorting the output. There's also a 100uF non-polarised electrolytic capacitor in the feedback chain which will likely have dried out by now. You should get this changed at the same time as any repair.