Google
 
 
 
 
   
The Art Of Vacuum Tube Maintenance 
by the TWEAK SHOP
 

 

Intro

So you've crossed that bridge and gotten into tubed electronics. Congratulations!

We carry a wide variety of tubes here at The Tweak Shop, with sources from around the world including Russia, Slovakia, and China. On the left are three of the fine power tubes we offer; an EL-34 from RAMLABS (whose remarkable testing procedures are highly acclaimed among the tube audio cogniscenti), a Teslovak KT-88 (from the revamped Tesla factory), and a Svetlana 6550C (from what is arguably Russia's largest tube manufacturer). We also recommend (and sell) tubes from Gold Aero and SovTek.

There's a few things you should know now that you've chosen this rewarding audio path, and that's what this page is for: To explain the basic care and feeding of your tube components.

First of all:

Handling vacuum tubes

Simple: DON'T. Tubes don't appreciate contact with oils and such from your hands. If you have to remove or replace a tube, make sure your hands are clean and, even then, use a tissue to grasp it. Oils and dirt build up on the glass envelope of the tube, eventually causing it to run hotter than it should, shortening its life.

Never handle a tube when it's hot. Before trying to remove a tube, make sure the component is turned OFF and UNPLUGGED and the tubes have time to cool (usually just a few minutes).

When removing a tube from its socket be sure you don't jam it back and forth trying to pry it out; gentler is better, here. Grip the tube firmly by the base and pull straight up while gently rocking it a couple of millimeters from side to side if necessary. You should be able to remove even the most stubborn tubes in this fashion.



Cleaning vacuum tubes

Over time, most tube pins begin to oxidize, and it behooves you to give them a good cleaning at least once a year. This can be accomplished with any number of good contact cleaners (like Kontak) or with good, clean Isopropyl alcohol (96-99% pure if possible; DON'T use rubbing alcohol - it contains minerals and oils that tubes don't like). We recommend using wooden-handled Q-Tips for the actual application and scrubbing (the paper-handled Q-Tips fall apart under pressure). If you still have some of the original Tweek Contact Enhancer around, good for you, but DON'T use it on tube pins. Tweek is not at its best in high-voltage applications.

Sometimes the easiest way to re-establish good contact for the pins is simply removing the tube and putting it back in! This often cuts through the oxidation and re-makes the contact.

Tube sockets should be cleaned as well. We recommend (and sell) the tiny socket brushes designed specifically for the job by DynaClear. Their small size make it easy to get into the tiniest of sockets. (Again, not to state the obvious, but please only attempt this while the amp or preamp is turned OFF and UNPLUGGED!).

Should i leave my tubed component on all the time?

In 95% of the cases, no. There are a few components out there (like the Audible Illusions preamp) that have special circuits that provide a "trickle" voltage to the tubes, even when the component is turned "off". This does two things: It prevents the tubes from being "slammed" into operation when the unit is on, and it also means your "warmup time" to optimum listening is considerably reduced. Components like the Audible Illusions preamp are, therefore, "on" even when not "turned on", but this is a rarity.

In an ideal world, we'd all use massive Vari-Acs to slowly bring our tube equipment up to operating voltage. But that's an impractical fantasy.

It's something of a trade-off. Tubes don't like being turned on and off, but they also don't like being left on all the time just cooking. So it's sort of "six of one/ half dozen of the other". We think the tubes will last longer if not left on continuously, and many components feature a "soft-start" circuit that helps lessen the shock of turn-on.

Bottom line: Unless you really do listen to your system 18 hours a day, turn off your tube gear and prolong the life of your tubes.

Situating tubed components

In case you haven't noticed, tubes get HOT! The single thing that will shorten their lifespan is making them run even hotter than necessary, so make sure the unit is installed someplace with good ventilation. This DOESN'T mean a wooden, designer-type cabinet with closed doors on the front and a small hole for wires in the back! Open equipment racks and simple amp stands may not be the last word in stylishness, but it's a safe bet your tube equipment will last longer and even sound better with an equipment rack designed for the purpose. If you HAVE to put it in a cabinet with closable doors, always leave the doors wide open when the equipment is on. (This is even a good idea with most solid-state components.)

As to the various forms of isolation feet, we have a rule of thumb: Sorbothane (or equivalent material) pucks under tubed preamps, and either cones (with solid metal tips) or a combination of cones and pucks under tubed amps. When choosing the soft, Sorbothane types, remember to provide enough of them to support the component without having them "squish" down to the point of losing their damping qualities. In some cases, proper placement of support is critical for best performance. ASK us about this; every component is different.

Tube tweaks

There are only a few things we recommend for improving the performance of tubes or prolonging their life. High-temperature "O" rings, like those from Music Reference and 3M, are good for damping the glass envelope of the tube and cutting down on microphonics (in some circuits you can actually hear the tube "ring" when the component is tapped). We can't recommend use of Sorbothane rings for this purpose and the reason why is simple: THEY MELT! We've seen examples of this, especially when used in preamps that run hot, where the Sorbothane melted down the sides of the tube and onto the adjoining parts and circuit board. Worse yet, once melted, the stuff STAYS melted, making for one hella mess. We also aren't too fond of devices that you have to glue to tubes with silicone or such. There are even some devices that make the tube run HOTTER! Is this a good thing? Of course not.

Then there's the Pearl Audio Tube Coolers. They do what they claim and are simple to use. WHAT A CONCEPT! Tube Coolers are made of very thin, anodized copper that's shaped like accordian-style fins with little vents built in to create a convection current that actually draws the heat away from the body of the tube. Sounds weird but they really work. Theoretically, dropping the operating temperature by almost 100 degrees (as Tube Coolers do with a standard EL34 power tube) can QUADRUPLE tube life. Tube Coolers also have damping properties against microphonics because of how they're held against the tube's glass envelope. Call us (at 707-757-8626) for information regarding your particular component and the appropriate Tube Coolers.
 

Outro

Well, that's enough to get you by. We've been afficianados of tube gear for a long time so, if you have any questions regarding their maintenance, give us a call at (707) 575-8626.

Otherwise, enjoy!



 


 
© 1997-2013 HIFISHACK. All rights reserved