Thanks for all the feedback. I cleaned all the sockets with the De-Oxit cleaning kit. On very close inspection, I found a couple of socket contacts that were bent/loose. I gently bent them back with a very slim awl and presto, no more problem. I noticed the tubes inserted much easier after the De-Oxit treatments.
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.
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.
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http://www.kontakaudio.com/kontak-audio-cleaning-fluid.html
I had been using Kontak cleaner to clean any contact including pin of tubes for more than 20 years. The nice thing is it does not leave any residue and improve transparency. Thomas |
Thanks guys - I ordered this: https://www.tubesandmore.com/products/vacuum-tube-survival-kit-caig-deoxit-gold I’ll clean first and then tweak the contacts if need be. Being 16 years old maybe it just needs a little cleaning. |
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. |
Agree, tweak the pin pockets. There's also some very fine pipe cleaner type wires that can be used to clean inside. Had mine so long, forget where they came from. I would also try and find a wire, same gauge as the tube pins, to slide into each pin pocket individually to figure out which one is loose. If you have an old tube on hand to sacrifice a pin that would be the way to go. |