My Crack with speed is dead silent at the highest volume level. The folks at BH will help if needed. Checking the solder joints is a a good idea, nice and shiny etc…wires should be crimped tightly around the terminal, tab etc before soldering, the key here is solder alone doenst cut it all the time, a good mechanical joint then solder applied well is the secret…
The Crack’s tube sockets are IMO a weak point. Its not a bad thing sonically, but many people swap out tubes looking for that perfect NOS tube…this removal and insertion moves the pins around the base of the socket, and things that are not soldered well or with no “strain” relief can over time crack and even break, especially those small red leds you have to install in the socket space…
You can post some clear pix at BH and Paul and the guys will look and offer some assistance…
Good luck should be fairly easy to track down…
Alex