[tianguis]

Hi, all:
      I've posted about my experience rolling NOS tubes, primarily early 1950's triple-mica USA 5751's and 5814's, Mullard and Amperex Holland 12AU7's, rectifiers. I've since had experience of Teles, RFT's, Tungsrams, JAN, Sylvania GB's in all flavors.
     My previous posts about differences still hold water -with a caveat.
     CLEAN THE PINS MECHANICALLY!
     In preparing some NOS tubes to send to a friend (poster, here) I ran into difficulties: tube "rush", popping, banging, distortion, you name it. Happened with old-favorite tubes, too. Tubes I'd used for months threatened to blow my speakers when placed back in the circuit.
      I thought about it overnight, thought it might be pin corrosion, got out the Dremel (soft wire brush) and cleaned the pins of all the Cornet's tubes.
      The difference is nothing short of astounding. I know now it's my fault, but I've been chasing a channel imbalance for months. With clean pins, GONE.
      Same tubes, cleaned, throw a much larger soundstage with far better frequency extension at both ends. Much quieter, also.
      You don't know what you've got until you can hear it.
      I suspect the same is true for new-production tubes, which have oxides and/or scale on the pins due to the manufacturing process.

Regards,
Larry Welsh

[pretzel_logic]

I tried a couple Mullard 12AX7's that tested fine in my Cornet.  The amps were already warmed up and I fired up the Cornet, tube rush...pop...bang, scurried to get to the selector on the pre and then turn off the Cornet.  Cleaned the pins and tried again, the Mullards are fine.  Cleaned the rest of my tubes today too so will see how much of a difference it makes.

Brian

[tianguis]

Pretzel:
     Glad it worked for you. I've since gone on to clean all the other tubes in my system: 2 300B's, 2 6SL7's, 2 6SN7's, 2 EL34's, 3 more 12AU7's, 2 12AT7's, GZ34. The improvement was well worth the effort.
     I realize that this sort of thing is pretty basic to keeping tube gear sounding as designed, but it seems a few folks don't pay it much mind.

Regards,
Larry Welsh

[clivem]

I'm a believer in cleaning tube pins, especially NOS that are typically discoloured - oxide coating. I picked up a tip on another BB a couple of years ago. A fibreglass pencil works really well for this. RS part no: 514-868.

Regards

Clive

[nature boy]

Great post for tube rollers.  You definitely have to clean the pins on NOS tubes.  Those with tubes in their systems have two choices:

You can use some some small nylon wire brushes with some Caig DeOxit, this gets about 85-90% of the grunge and oxidization build up.

Or

Put a dremel on you holiday wish list.  

Cheers,

NB

[Carlman]

Clivem, thanks for that tip... I've been using the Dremel with wire brush method for a while.  I also spray some pro-gold contact cleaner/whatever on the pins and in the sockets whenever I'm in my pre-amp.  

The only problem with the Dremel is if you slip up and let it bend a pin.  I know it's not that big of a deal but, sometimes I'm clumsy with a Dremel... especially after a morning of coffee.

Sandpaper takes forever and doesn't form around the pins very well.  I recently tried cleaning my pins because of roaring static in one channel.  

Things got better but, didn't fix it.

I cleaned the sockets with a Dremel attachment that basically looks like a point tip with diamond grit on it.  I used the attachment only, by hand, to rotate in the sockets a few times to get them very clean.  However, I'm pretty sure the sockets need to be replaced... Some of the pin connectors were looser than others.

The sound is better but, I've still got the static/roaring noise when playing through those particular sockets.... I tried a few tubes and it's definitely the sockets that's causing my issue.