Hi I have Dared MP -30B Tube amp I bought new since 3 years back, last 2 years not used. Recently I had try to connect my speaker I found input selector switch stick could not turn, than use WD40 clean volume control shaft sticky grease than turned freely. When I powered up I have notice right channel no sound! I have done troubleshooting following steps. When tuned on power all tubes glowing, seems power supply is good, checked each channels fuses found good, then I swapped main tube 300B between left to right no improvement, swapped pre tubes 6N3 2nos left to right no improvement, I had measured out put transformer from speaker terminal positive 4 & 8 ohms to negative impedance compared left and right both the same, transformer input measured left and right no any different. Selector switch contact and volume control functions found all perfect. Still right channel no sound! Anybody can help solve my tube amp issues? I could not found any schematic any documents for this amplifier!