At a DIY attempt to replace a few parts, this fella stopped working. Here’s what needed to be done.

Cracked/loose solder joints here(input jack):

Here(shield behind pots):

Here(plug connectors):

and here(ribbon cables from tube board to main board):

After all those were cleaned up/re-flowed,  here’s a previous repair attempt to fix lifted/cut circuit traces that was also cleaned up/repaired:

It was tested after this. Though signal came through, it was very faint. I removed the old solder from the preamp tube sockets and re-flowed those with new solder. That did the trick and this amp came back to life.