Under no circumstances should you try and do the maintenance of Hehku by yourself. You should especially avoid opening the amplifier, since that leads to termination of the guarantee instantly. Hehkus may hold life-threatening electrical tension inside them for hours after removing the plug from power grid and this power is deadly. The only maintenance that you can perform on your Hehku by yourself is keeping it clean and changing the visible tubes. Changing of these tubes requires removing the back panel and that is the only part in your Hehku you are allowed to remove gently. In all other scenarios, get in touch with a professional.