hifi engine

Sony TA 4300f

Anyone know off hand, what might go bad on these? Had it running a three way system (Dynaco st 70 , Motorola El84 console amp & a solid state for LF. ) something popped an then no signal to mid drivers. Thought it was the rectifier tube on the dynaco but after replacing that amp with a tripath amp on hand I found a very weak signal to the marantz SS I use to drive the LF drivers. I don't want to send this out for repair blind and get fleeced. Thanks in advance for insights into this problem.
The dynaco rectifier might have gone as well. I am trying to put together a passive crossover but lost a lot of gear in hurricane Sandy.