David,
I worked on many 8660's and only once did I come across a buzzing power transformer.? The customer complained about it and as it did uncharacteristically buzz.? ?(no recollection if it had opt 003) I replaced it and have it in a home made power supply that I built at least 25 years ago.? ?I use the 5V winding, full wave bridge rectified and filtered it is capable of > 20 A at 13.8 V to run a 100 W HF ham band transceiver.? ? The 8660's power transformer is sealed in a gray case (mu metal?) and I thought it might have been potted.? Maybe there are voids in the potting or it was not potted in a sufficient vacuum.? ? In my homebrew power supply it doesn't seem to buzz loud enough to be a problem but I did place it under a bench so maybe it still buzzes:)
Pete
