by logos47 » Mon Jan 09, 2017 8:08 pm
EW and Tom, thank you so much. After the suggestion of unplugging signal input from the unit (which is now on my friend's bench across town), I took the "good" unit and swapped in the linestage IC from the faulty channel and voila--the nasty sputtering hash was now in the previously quiet MKIII amp. The problem was from the linestage (nicely done RCA New Orthophonic in a PAS chassis). Evidently, fader lube got into the function selector switch (long story)...so a good deoxit cleaning and pin tightening cleared it all up. Thanks to you, I used the tools at hand and am in business. I think I'll get Michael Geier's "How to Fix Everything Electronic" and get an oscilloscope if I'm to satisfy my addiction to the sound of my all-analog rig of 45 years (and keep my wife and friends). Cheers!
PS: I've got two 5751 Sylvania triple mica bp--a nice tube. I'll try the 12BH7 along with it.