The other day one of my amps failed to power up. This surprised me as it had been playing the night before. Looking closer I noticed a 6SL7 not lighting up, substituted another in its place & I was back in business. I was feeling fortunate that a tube was all that was wrong but concerned about the cause of the failure of a somewhat expensive valve. Maybe I’ve learned this trick here but here’s what I did. With the tube sitting pins up I warmed up my iron & applied some heat & solder to the holes in the centers of each pin. Now in retrospect I probably could have tried just heating up the pins with no additional solder ( I had to clean up excess solder from the exterior of the pins) or used a meter to see which pin was open but felt it was good to practice getting solder down such a little hole. In this case I was lucky enough to be successful & that tube is back in place sounding like it never missed a beat. So if you have a tube go dark as opposed to red plating & going nuclear give that a try before discarding.

It’s an old fashioned octal thing like lacquering loose bases to maintain pin connections.