Hey Andrew/ Martin,
Andrew: will do a test in the next couple of days and a video. I am thinking also about one particular capacitor I did not change which is located under the Bias pot meter. When I refurbished this machine few months back, i hav changed all the old electrolytes caps, I did not touch the Philips mustard caps, however, there were a few of Wima bombs and other electrolytic s at the Bass/treble pots, gone bad....I remember, I have left one o.1uF cap at the bias, which was a black plastic casing cap...might this one also could be something to do with it?
Martin: thanks for your note. I have powered on the unit for 30 minutes before I did the test recording/run with these weird symptoms...machine itself was quiet warm...just don't understand that half of the song i have recorded did this moving/whining sound, like slowing down/speeding up motion evenly, then suddenly, at the half time of the song recorded, everything was fine.
Tape was a brand new sealed, 2012 year made "fresh" Quantegy..
thanks guys!