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In Reply to: I can't seem to get my pre-amp tubes seated properly posted by newanvil on April 24, 2007 at 15:18:23:
I would suspect the tubes have oxidized or dirty pins first. That's something that doesn't get mentioned enough when rolling NOS or used tubes. To make matters worse, you can stick a tube with dirty pins in the socket and contaminate the socket if the gunk transfers.Having said that, I've had small signal tube sockets that just don't seem to grip the pins very well and require a little wiggling...even with clean tubes. It just so happens that the Cayin that I used to have required it and the tube was quite loose in the socket. Cayin and Primaluna are made in the same factory, btw.
Follow Ups:
Hi,I would venture to say that the stock current production tubes have marginally greater diameter pins than the NOS tubes. This has loosened the sockets for your tube rolling. Additionally, I find that the chinese tube sockets are nowhere near as good as good old american micanol sockets for spring tension.
With the unit unplugged and capacitors discharged (if you don't know how to do this...don't) use a dental pick to gently pry the receiving pins of the sockets tighter. Problem solved. If you go back to current production USSR tubes plan on doing this again if you tube roll.
Not everyone has a set of Dental tools (I do, came in an antique porcelin topped drawer cabinet) so a much more common heavy sewing needle can suffice; if you do not have one of these, chances are the neighbor lady or your Mom or Auntie do. You just need a sturdy tool that will slip into the small space between socket & gripper. Be careful prying against micanol or phenolic sockets so you do not flake off fragments of the socket.
> > .
nt
"David! You can KILL a man with a chopstick!" -Keith Charles, Six Feet Under
Prying the metal collars/contacts inside the socket holes is NOT a good idea unless you know more about the sockets. Some of them are really cheaply made and the copper is thin or brittle. It breaks. Then you are really up s-it creek without a paddle and skip the next para.I have been through the mill with floppy tubes. The first cheap things to do are: clean the pins, bend the pins a bit for a tighter fit (also dangerous), stuff socket holes with tiny pieces of alum. foil. (Be sure to put tape over the center hole if there is one).
The best and most expensive thing to do: get a good technician to replace the sockets with better ones that have smaller, springier, collars/contacts.
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