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
Why put dielectric grease on the pin holes? It seems like that would do more harm than good.
I agree with Zd542, di-electric grease would reduce contact surface for each pin. In my business, truck and truck equipment sales, we use di-electric grease to protect electrical connections from moisture infiltration.
When I clean my system each year I use Caig cleaning brushes in each hole on each pin with Cardas Contact Cleaner, and feel I get good results.
Just my opinion of course
Keeping the pins in the socket tight is the best tip I can think of especially if you roll tubes. Also reseating the tubes can clean off some oxidation.
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). The input is appreciated and hopefully some members will remember this in the future. Perhaps sans the grease application.
A lot of guys use Walker Audio Super Silver Treatment SST.
I clean resistor leads, capacitor leads, internal hook up wire, tube sockets etc, with 99% alcohol. About once every two months.
"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.
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 ;-)
Swampwalker, yes of course they iron but they don't do windows.
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!!
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.)
"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 ) ."

When you go to the auto parts store to pick up the brake clean, get a can of penetrating oil and lube the moving parts in the amp. If the hum goes away, take it apart and use something more permanent like wheel bearing grease or anti seize.
"When you go to the auto parts store to pick up the brake clean, get a can of penetrating oil and lube the moving parts in the amp. If the hum goes away, take it apart and use something more permanent like wheel bearing grease or anti seize." Zd542

Ouch! That hurt Zd542! Contact cleaner it will be!

Dielectric grease:
Dielectric grease is electrically insulating and does not break down when high voltage is applied. It is often applied to electrical connectors, particularly those containing rubber gaskets, as a means of lubricating and sealing rubber portions of the connector without arcing.
Give you one better than that. I've always had a hum coming through the Premier 15 (phono) into my Premier 16 and Premier 12's. Suffice it to say I tried everything to get rid of it. BTW, I have 4 dedicated circuits. Recently I replace the floor in my listening room. I had to breakdown and move all my equipment to do so. It's now back in service, wired identical to the way it was before, and the hum is gone. I guess "a few inches can matter" :-)
I guess I should check the sockets on my 1960 Fender Deluxe…they could be an issue someday.
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...
"Dielectric grease:
Dielectric grease is electrically insulating and does not break down when high voltage is applied. It is often applied to electrical connectors, particularly those containing rubber gaskets, as a means of lubricating and sealing rubber portions of the connector without arcing."

Yes, but understand that definition is most likely referring to cars, and not high end audio systems. Under the hood of a car is an extreme environment for electronics and cables. The di electrics break down over time and the grease is used to "help" the aged components last longer.

Here's an actual example of what its used for: http://ww2.justanswer.com/uploads/kennyz1963/2009-11-01_144226_tsb06-09-03.pdf