Not something I normally do but as it was for a mate I thought I’d do it anyway. He had a lot of scratchy controls and the output of the clean channel was fluctuating quite badly. My initial hopes of this being caused by the noisy controls were dashed when the problem persisted after all the controls had been stripped and cleaned. Being a valve amp of over a decade old my thoughts turned towards the preamp valves…not the outputs as the dirty channel worked just fine. A new set were fitted and everything sounded lovely!