After success with my first 500C restoration thanks to help from knowledgeable people on this forum, I pulled out the 2nd of 3 of these I've had in storage for many years. It's serial No. is in the 55K range. A heavy layer of tar and nicotine covered the chassis. So, my first order of business was to remove that, as I HATE a dirty set. Except for the output tubes every tube in the set is an original Fisher. The 7591s were missing so I put in a set of EHs. No under chassis components have been replaced--all are original. I then powered it up gradually with a Sencore PR 57 variable isolation transformer. Running at 90 VAC, and an MP3 player into the Aux input, this baby sounds perceptibly better than the one I just restored. No hum. Absolutely no distortion and maximum volume on both channels. (I haven't yet done any cleaning of pots or switches yet, either). Were it not for the need to make recommended improvements to prolong tube life and provide safety, it seems a shame to tinker with this 500C. Really mind blowing how good it sounds. So Avery's engineers knew what they were doing--without a doubt--and they must have used good components, or there would have been some failure after 55 years. Another vote here for the great 500C.