This is my first tube amp, however am pretty handy with a soldering iron and troubleshooting. However my lack of knowledge is leaving me stranded.
Anyway i got this st-70 and immediately replaced the quad cap (with an exact replacement) and all other capacitors with orange drops of the stock value.I also replaced the selenium rectifier with a 1n4007 diode. i then bought a matched quad of jj tesla's el34's that were all marked 26/5.0 on them. My problem is that i can't bias the tubes, they only bias up to about 1.44 before the potentiometers max out. Also there is a hum when i first start up the amp for about 5 to 10 seconds then goes away completely and doesn't come back.
Can anyone help me out as to were i should start, as i really wanna listen to this thing!