Hello, I have a pair of Eico HF-60 that I have problem biasing them. I have follow the instruction as close as I can: Bias to -47 VDC match the meter to zero Bias to 0.65 VDC from the meter probe. No matter what I do, the tube in the back always have a little red plating going on. I have a very good multimeter that very precise, and I have get the value as close as possible. I know all of my tube are good (tested with calibrated TV-7/U tester). If anyone can please point me out to a right direction. Everything in the amp is original, I have tested all the cap and they tested over the rated value (50 mFD tested around 60 mFD)? I don't know if that affect anything.