Vox Cambridge 30 twin loss of power

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: I bought a cambridge 30 twin for a small light amp because I was sick of carting my ac30 around. I played it in the shop sounded great and had enough volume for what I was going to use it for. Took it to a solo gig and after 30 mins it just lost all it`s balls. I was left with a scratchy gutless sound that couldn`t even provide background music. I have since found out that this is common and that there is a replacement chip to give the amp more power. Does anyone know anything about this?