Cleaning tools for Power and Preamp Tube Sockets

[nevetslab]

Having just recently repaired a brand new Fender Twin Reverb combo amp, where the complaint was 'Play Low E string loudly on guitar causes loud transients. After moving it up onto my checkout bench, powering it up, then taking it out of Standby, first thing I heard was substantial hum with both volume controls fully CCW. And loose Fuse Holder. So, I'd be taking this apart to get the chassis out of the cabinet. But first, I gave it a good whack on top of the cabinet, which reacted with loud barking noises with every whack. YUP. Been down this road before.

Pulled the rear upper panel off, then carefully depressed the stiff Bear Trap clamps releasing each of the power tubes, set them in order in my holding box. Fetched my X-Acto knife with a #11 blade installed, and one pin at a time, scraped the sides of each pin all around the circumference to yield clean surface on each pin. Pushed the tubes back into place and powered back up. Pounding on the top of the cabinet this time was quiet without the loud 'objection' to such vibration-inducing blows.

What I haven't really come up with is a good proper-sized round shaft that has a grit-surface to it. Blank Drill Rod, #61 size (0.039" dia) for the Preamp tubes and #43 size (0.089" dia) would be suitable sizes. What I haven't figured out is how to turn those smooth surfaces into a fine harden grit surface as though it was a suitable grit one might have on emery cloth. Would sand-blasting the blank drill rod yield such a surface? I'd first want to round off the end of the drill rod's blunt end so it easily slips into the tube socket's mating contacts to be cleaned and burnished.

I've used wooden shank Q-Tips as cleaning rods, dipped into Caig DeOxit in the past, along with back end of those two drill bit sizes, fitted into a Starrett Pin Vise.

[Helmholtz]

I do not recommend to use anything abrasive or scraping on plated contacts like tube sockets.
As already mentioned in an earlier thread I use different size interdental brushes wetted with Deoxit D5 to clean tube socket contacts with great success.

[stokes]

Agree with Helmholtz about the abrasive. I use pipe cleaners with a deoxit or similar contact cleaner.

[Tom Phillips]

I also agree with Helmholtz about the abrasive. I too use the interdental brushes on the 9 pin sockets and larger brushes on the 8 pin sockets. In difficult cases, after D5, I clean with IPA until the brushes come out clean when wiped on a white cloth. The final step is a light coat of preservative. The last two steps are not always needed but they do produce longer lasting results.

[Chuck H]

You could create an abraisive surface on the drill rod by rotating it in a piece of folded sandpaper. Modern zirconia sandpapers are MUCH harder than the older aluminum oxide paper and can cut into the rod surface more effectively. That said... I agree with others that any hard abraisive should be avoided. Abraiding the contact surfaces can damage any plating, potentially exposing mateial MORE prone to oxides and also increases surface area without increasing contact area so the surface can hold more contaminate sooner reducing the effective time between services.

I don't have the dental brushes mentioned above but I've done alright using toothpicks for sockets. The porous wood is as abraisive as I get here and they're typically stiff enough that I can tweak the the little springs in a little while I'm at it.. I just use cotton swabs on tube pins. I'm using whatever de ox product I have (I think it's a generic Radio Shack product). It seems to work fine but I've been waiting to run out of it so I can buy the Caig products endorsed by the pros here.

[Delta362]

I do the same as Helmholtz. I have one size for the octals and a smaller size for the noval ones.

A trick I've been doing with the DeOxit D5 is to spray it into one of those small medicine cups as I feel there's too much overspray with the dispenser. I dip the brush in small medicine cup, then brush about 3 or four of the sockets before dipping again and repeating.

If I need to tighten the sockets, I use a dental tool.

[Mick Bailey]

In general, socket pins are plated and the newer the socket the thinner the plating. I have had some sockets that had an unplated copper alloy that was very springy and also corrosion resistant. They may have been military or industrial surplus. The challenge with cleaning is to remove only the surface corrosion or contamination back down to the remaining plating thickness. Dental brushes work well, especially if the contact cleaner has some chemical property other than being a solvent/lubricant. I had a can of really effective stuff from Kontact in Europe but it lost pressure and I decanted into small dropper bottles. I'm now on the last one, though. It would be nice to get some micro brushes in phosphor bronze for really corroded contacts - like miniature gun barrel brushes the size of dental ones.

[nevetslab]

The #61 and #43 Drill Rod shanks arrived this morning from McMaster-Carr. I chucked them into Starrett Collet Vises and then radiused the tips to replicate that of Tube Pins. I'll keep this with the smooth shanks and NOT alter the smooth surfaces as I first thought of. I too have a collection of interdental round bristle brushes and larger radial brush for the Octal Socket tube contacts. With the two Drill Rods, you can immediately feel if any of the tube socket contacts are loose fitting or not, requiring re-tensioning to restore the original tight fit with the tube pins. So, still makes for a useful tool, while I also have suitable brushes for applying contact cleaner.



Thanks for all the input.

[Mick Bailey]

The other aspect is the cleaning of tube pins, especially old preamp tubes which are still good. I've seen old ads for tube pin cleaning devices but they disappeared along with pin straighteners.

[nevetslab]

I've used brass bristle brushes, as well as X-Acto Knife #11 blade gently to scrape off oxidation to get to clean plating surface. I've never seen any radial brushes that surround the pin for an up/down scrubbing. I'd imagine some sort of sleeve that could be slipped onto small size duck-bill pliers that could do something like that. Never did see any of the adds you're mentioning, which probably was published in old component catalogs of the age. Somebody amongst us may have some ancient component catalogs that shows tools like thaat.

[Helmholtz]

It most often suffices the clean tube pins with some D5 on a piece of cloth/ tissue.or even a Q-tip (cotton swab).
In more severe cases I use a folded piece of fine grid (400 or more) emery paper or cloth.

[Chuck H]

The other aspect is the cleaning of tube pins, especially old preamp tubes which are still good. I've seen old ads for tube pin cleaning devices but they disappeared along with pin straighteners.

I used to have one of those pin straighteners. It worked a treat. I can't find it now after a couple of moves though so I'm back to making minute adjustments by eye and trial and error.