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Tube amp - tube socket problem

Hi fellow tube amp owners. Four months back I bought a used Primaluna Prologue 2 which I really enjoy listening to. I'm the 3rd owner and it was built in 2004. I have a problem with one of the preamp tube sockets. One day I was very lightly dusting the top while it was running. I barely touched the tubes, and I heard a loud pop/crackling noise. Turns out the left side 12ax7 socket is the culprit. In normal operation it's fine, no noise no problems. If I gently wiggle the tube it makes the noise. It then has to be returned to a precise position to return to normal. 

I contacted a local tech who said the sockets can become loose over time and/or get some contamination from the tube pins lodged down in there. He didn't seem too keen on working on it, but said he could try to clean it out. I wondered if there was a bad ground or short, so I opened it up and inspected all the solder joints involved with that socket and found nothing wrong. I don't really want to ship it to have it fixed if I can avoid it.  My main concern is that it could get worse overtime or lose some performance on that channel from not making good contact.

Any ideas? Has anyone had a similar issue? Thanks.
dtapo

Showing 1 response by atmasphere

atmasphere's avatar
atmasphere
12,116 posts
 
You don't need a new socket. You have three options.

1) remove the tube and ever so slightly bend its pins inward so it grips the socket more tightly.
2) Remove the tube. Using a tiny screwdriver, work the bit in between the socket contact and the socket material, in such a way that when you tweak the screwdriver, you are able to bend the contact in such a way that it grips the pin of the tube with more force. Do this to all 9 contacts on the socket (unless it uses octal input tubes like the 6SN7, then do all 8 contacts).

3) Remove the tube. Using DeOxit in the red and black can, spray the socket contacts and then work the tube in and out of the socket a few times. Use as little DeOxit as you can- the stuff in the red and black can leaves no residue harmful to high voltage circuits. Do not use any other type of contact cleaner unless you **know** it leaves no residue- otherwise the application can destroy the socket and contaminate the circuit board. Isopropyl works too but is less effective. Dab up any left over liquid with a cotton swab.


Just be patient and take your time.

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