All of our repairs are carried out to a high standard and are fully tested and stressed after everything is back together.  For peace of mind we offer a 3 month warranty on the bench time for the original fault, this excludes valves and loudspeaker replacement as we class these as wear and tear.  Repairs are carried out using the same size and specifications as laid out by the manufacture to ensure original compatibility.  We've often had people saying that they've read on a forum about changing values of components to change sound and amplifier characteristics - we would need to investigate this prior and ensure it is correct to do so as we have had some enquirers which would render the customer's amplifier useless and beyond repair had we have carried out their request from seeing a post on a forum.