the secret of NOS tubes...

[dai h.]

okay, not really

...but just wanted to relay something I noticed. Was getting a total crap sound out of the amp. Symptoms: bad sound, noisy, and some sort of rustling in the low freqs., and the ground lift sw. out of my Palmer PDI-03 made a difference in the sound and amount of hiss. Long story short, traced the problem to the old Sylvania 12AX7 I installed to try in V1. Thinking about it, it seemed like something was not grounded, so I cleaned the pins with ethanol and metal polish ("NEVR-DULL"--same thing sold under a diff. name here). Re-installed the tube and the weirdness went away (I'm thinking the plates were not *AC* grounded as they should have been). One thing that seemed to throw me off was that the tube itself (although sounding fine and a bit on the microphonic side) was apparently worn and lower in gain than usual. Guess that made things seem doubly weird. Anyway, something you might want to keep in mind when encountering a "bad tube". Oxidized and dirty pins.

[bob p]

nice tip, Dai.

i have to admit that when i've straightened the crooked pins on those old noval preamp tubes, i've encountered my fair share of glass chips flakingoff of the base. you've got to be careful.

i was wondering about your cleaning reagent. i'm not familiar with it. is it a liquid or a paste? how is it applied, and can you also clean the socket contacts with it?

after reading your message, i'm thinking about trying out a bottle of Tarn-X (essentially a chemical reducing agent) that has been sitting on the shelf in the laundry room for years and years. its a liquid, and it would probably be easy enough to dip the tube pins into a cap full of the liquid.

has anybody tried this?

[Enzo]

I clean old tube pins too. I use my Dremel. World's handiest thing.

I keep a wire brush chucked in the Dremel for buffing out jacks. Works like a charm. This is the wire brush where they all come out the end, NOT the typical wire wheel. Dremel #443. See stock 22-2031 at MCM:

http://www.mcminone.com/product.asp?...5Fid=22%2D2031

When it spins the wires flay outwards. It buffs the insides of the jack shaft, and polishes the tip contact when it gets there.

With a 12AX7, a quick trip around the pins inside and out with that same brush takes a few seconds and then they are shiny.

[stokes]

I always use a contact cleaner on the pins and while they are still wet,work the tube in and out of the socket with a circular kind of motion,cleans the pin and the socket at the same time.Years ago I tried a piece of 0000 steel wool on the pins and after about 6 mos the pins became very oxidized,I suppose it took whatever coating off the pins and sped up the oxidation.I have always avoided the abrasive approach since.The contact cleaner works fine.I have found that dirty pins on preamp tubes is very often the cause of a lot of noise problems in amps.

[dai h.]

Bob, NEVR-DULL looks basically like a big clump of cotton wadding (impregnated with metal polish) in a can (you pull out a wad of the appropriate size when you use it). I bought some after learning that some luthiers, techs, etc. use it for polishing frets. I also used a piece of fine emery paper, scraping lightly since the removal of too much of the plating (as stokes has mentioned) was on my mind.

i have to admit that when i've straightened the crooked pins on those old noval preamp tubes, i've encountered my fair share of glass chips flakingoff of the base. you've got to be careful.

definitely pin straightening can be tricky. *IMO*, one should NEVER use a pin straightener since it seems to me they put too much pressure on multiple points on the base. I am a bit embarassed to admit how many tubes I've cracked on mine, going, "well, maybe if I'm a bit more careful this time I can get all the pins on this nice NOS ****** tube perfectly straight". Or, maybe only use one if you know a specific tube's base is strong enough to handle it (since there seem to be differences in how strong the base is). I think something like a hollowed out pen straightening one pin at a time is safer for the tube.

I've also used liquid metal polish before on a bunch of tubes (some having very rusty pins), and one thing I didn't like about that was that some of the polish would run down between the pins and glass. However, (now years later) they seem to have held up okay. Probably if I tried that again, I'd make a paper shield of some sort to prevent that.

edit:

and the ground lift sw. out of my Palmer PDI-03 made a difference in the sound and amount of hiss

when it usually does nothing to the sound when engaged. (The Palmer chassis has a wire on it connected to the Portastudio chassis ground it is connected to which goes to an AC ground.)

[Zemaitis]

Might be safer and easier to soak the pins in OSPHO. Its a mild acid that is great for removing rust from chrome. It wont dmage paint, basically just removes corrosion. And it's safe for use around food.

I used it once to clean the rims on a car that looked like solid rust, and it made them look new. No harm to the chrome.

[bob p]

ospho? you mean like coca-cola?

[Zemaitis]

Originally Posted by bob p

ospho? you mean like coca-cola?

Nope... its a mild acid you can get at the hardware store, its a green color. Won't harm paint... I friend of mine who restores cars told me about it. Works great for cleaning guitar hardware too.

[bob p]

both contain phosphoric acid.

[PlayItAll]

I use Deoxit sprayed onto a little piece of cloth for cleaning pins, wiping off guitar plugs, jacks, spoons, forks... :-) Seriously, the stuff works great and a little on a little piece of an old t-shirt goes a long way.

[Bruce / Mission Amps]

Hmm... I never thought of using that as I thought that was used as a cleaner before primer on bare metal.

[petemoore]

It's all in the 'motion'.
When bending pins back in shape...
The tube pin can take very much pressure directly to the side, 'leverage' motion though puts major stress on the the pin and edge of the glass hole.
Using your thumb on the end of a lever will break the glass more than 'tortioning' the pin {I use small needle nose flat blade pliers] so the side of the pin cylinder mostly pushes evenly to the side of the glass...the right bend 'n twist motion...
Gripping the tube firmly, and tortioning the pin just right...I still break off some glass sometimes...lol.
Often it takes mostly straightening, holding the tube loosely, and clamping the pin in the flat blade pliers from different angles can take bends out of the pin, as long as its' not angling out of the tube.
The last little bit of angle straightening can sometimes be done as the tube is being installed...in this way you don't have to bend any farther than 'that' to get it to go in the hole, bending to perfect straight may mean overbend so it comes back to straight..they're not to springy, but the less bending the better.

[JJGross]

Originally Posted by bob p

both contain phosphoric acid.

Yeah, but one of them also has corn syrup and caramel.
Probably counterproductive to 'cleaning'.

[Marc]

I like using the progold pen applicator. It has a fiberglas tip that wicks the progold to the pins and the tip gently cleans the pins. It's pricey, but lasts a long time I've been using the same pen for 3 or 4 years. I think ratshack may still sell them... I first tried it when lord valve sent the 1" square cloth sample with an order I placed years ago.

Marc