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Tube Amp Maintenance Tip...

Interesting maintenance tip story.....My C-J LP66S amp has been creating a 'variable volume sign wave' type hum in my speakers lately. The hum did not go away with warm up. I pulled the 4 power tubes and 3 signal tubes out of their sockets. I blew out each socket and pin with Can-O-Air. I also pulled the two fuses & blew out the holders /holes. Then I applied a very thin coating of Di-electric grease to each tube pin hole. Finally, I crossed the 4 power tubes (6550) left to right and just rotated one position each of the three signal tubes. Performed a re-bias once the amp powered up. No new parts involved, let's just call it a 'dusting & cleaning'. Long story short, issue resolved. Not sure what I did to correct the noise or why it even started. Perhaps a mote of dust in the wrong place? Moral: If your having some noise issues with your tube equipment perform some basic cleaning procedures prior to going into any type of panic mode. Hope this helps someone in the future!
quincy

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,574 posts
 
You really want to be careful about treating tube sockets with chemicals! If the chemical uses any sort of oil base the socket can be contaminated and problems (perhaps failure of the tube and requiring replacement of the socket) can ensue.

For this reason I use spray 'contact cleaner with silicone' such as Radio Shack used to sell. That's about as active as you want when cleaning tube sockets!!
atmasphere's avatar
atmasphere
11,574 posts
 
A good tube socket will have tin-plated pins and will last decades as in Wolf's Fender. These days we are seeing a lot of cheap sockets with silver plated pins- they will not last very long at all. Sounds counterintuitive, but in fact tin does not want to corrode and is a lot harder than silver or gold.

Hum and tube rush are not the same thing by the way...
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