My aging Carver amps are....aging. Developing some transformer noise so have idled them for now. Had a local general electronics tech go thru them fairly recently but he found nothing particularly wrong outside of some display lighting issues which were obvious. Later on one of them developed some transformer noise....but they're almost 40 years old, too (M-500t models, have two, my older M-500 went up in blue smoke a few years back).