Keep those power tube socket contacts tight!

[MacFangus]

This is part of a reply from another post, but I think it's deserving of its own thread.

 

This goes for any 8 pin power tube amplifier... Make sure that the power tube socket commutators are tight! Many of today's tubes use large diameter pins that spread the contacts open. When you replace the power tubes with a new set that has smaller diameter pins, you will end up with a loss of continuity. If you lose contact at pin 5, the tube will red-plate, thereby trashing that tube. JJ tubes have some of the largest pins I've seen. That, or they are putting an excessive amount of solder in the pins... Either way, you need to make sure the contacts are tight before replacing the power tubes.

 

Tools: Make sure the amp is unplugged, and discharge the power capacitors. Use a stainless steel dental pick to pull the contacts together. It takes some time, but it's well-worth the effort.

[WRGKMC]

It depends on the quality of the tube sockets. My old Black Face Bassman has high quality sockets which retract and have lasted 50 years. I think I may have tweaked the pin clips once in that time, and it was done as a precaution during routine maintenance, not as a necessity. The tubes face down and they see allot of heat too. The pin clips are rolled steel and fairly thick.

 

Those sockets were built to higher military standards. Many newer tube amps have all the components made in the orient. The contacts are made from thin low quality stainless steel or some other recycled metals that llok like it. When its heated by the tubes the steel looses its memory and flexibility. Its not the fault of the tube pins being different sizes as much as it is the metal used for the connectors themselves being total crap. Vintage sockets used to cost a few bucks back in the day. Many new sockets only cost a few dimes. You even have a hard time finding the better sockets with rolled steel pin clips.

 

I've had many of the cheap ones back when I did amp repairs for a living that would snap off with the slightest bending so I'd beware with your advice, otherwise you may wind up having to replace tube sockets. Cleaning them with a good non residue cleaner can fix most issues. Sticking with the same tube brand is helpful too. Preamp tubes can loosen up too. You have to be real careful reforming those clips too, even with the vintage stuff.

 

You know on the old sockets you could even buy new clips? You'd trim them off close at the terminal then collapse the clip and pull it out. You'd then insert a new one and re-solder the wire to the bottom. This was handy for amps that had the sockets riveted into the chassis. Drilling rivets out and replacing the sockets is a bigger PITA. I've done many and it was easier to replace the clips in those cases.

 

Still comes down to how often you have to mess with it. As a tech I'd only see amps with major issues so I'd do that kind of work on a regular basis. As an amp owner, how often do you have to replace tubes? If you're testing different ones out to find your tone that's one thing. Regular replacement on a combo may be higher too. The last set of tubes in my Bassman lasted me nearly 15 years, and even then the power tubes were still working fine. Even when I played out regularly with that head I was getting several years out of the tubes.

[MacFangus]

I have some NOS McMurdo sockets that I'm going to install in my Marshall 6100LM. I put a new set of JJ's power tubes in tonight, and lost continuity on one of the tubes... I tightened the contacts, reinstalled the tubes, and she's operating fine.