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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
zd542
5,339 posts
 
"10-25-15: Quincy
Yes, I had some reservations in regards to the di-electric grease, but it is a good conductor and used on very sensitive electrical connections in automobiles. (connectors on oxygen sensors for one example)."

You have it backwards. di-electric grease is not a conductor, its a di-electric. That's why they call it di-electric grease in the first place.

Cars are a different application. Its used as a sealant . As a car ages, things like plastic connectors and harnesses deteriorate and loose the ability to fully insulate electricity. And when that happens you get arching that can do a lot of damage. Think of it as wrapping an exposed conductor in a piece of wire with electrical tape, so it won't make contact with metals that conduct electricity.
swampwalker's avatar
swampwalker
5,138 posts
 
I clean resistor leads, capacitor leads, internal hook up wire, tube sockets etc, with 99% alcohol. About once every two months.
Whoa, baby! Do you iron, too ;-)
phd
1,314 posts
 
Swampwalker, yes of course they iron but they don't do windows.
atmasphere's avatar
atmasphere
11,784 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!!
quincy OP
350 posts
 
Excellent feed back....Thanks! Looks like I'll be spending the evening with some cotton swabs and some Acetone solvent cleaning pins and sockets. May try some Freon Brake Cleaner as well.

All that I am currently experiencing is a very soft hum from the amp through each speaker pair and through each speaker (low, mid, high ) . I believe this is normal tube rush? Can't hear any hum with music playing. Any thoughts on that issue? (Amp always had a bit of hum from the factory, but that does not make it OK.)
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