So I did two mods on my Dynaco ST70 and now the right channel is silent. Any help woud be appreciated! I replaced the rectifier tube with UF4007 diodes. and used a 10w/50ohm resistor on the output of the diodes to bring the voltage down a bit. I also added a CL90 on the AC wall line, before it hits the fuse. I also added two .22uf input caps to remove with any voltage that may be on the input when using various preamps. The voltages all over the amp are great. Except for the right channel. The two right channel EL34s both read only about 100vDC on pins 3 and 4. They should be around 410vdc each. For the diode mod, I just put a diode from pin 4 and from pin 6 to one end of a 10w/50ohm resistor. Then ran the other end of the resistor to pin 8. The voltage reads as it should. For the input caps, I followed audioregenesis's instructions: 1. Remove the two 470K resistors currently at the input jacks. If you do not have replacements, remove them carefully, as you will reuse them in step 3. 2. Remove the two wires currently connected between eyelets 7 & 17, and their respective input jack. Install two .22 uF 100 volt caps of your choice in their place. The voltage rating of the caps should be kept low to keep the size small. 3. Reconnect one of the removed 470K resistors directly between eyelets 10 & 17 for the Right channel, and the other between eyelets 7 & 8 for the Left channel. 4. Install two 1 meg 1/4 watt resistors in the positions originally occupied by the two 470K resistors in the original build. This procedure effectively places an appropriate coupling cap in series with each input of the ST-70, so that any low level DC that might be part of the input signal is blocked, and can no longer induce any LF instability.