Jay Lawrence is the amp tech at Gibson Pro Audio and in the coming months he will be a contributing writer to the Gibson Pro Audio Live blog. Jay will be imparting tips and tricks to keep your rig running!
In this first installment of “Amplifier Maintenance Tips”, we will discuss some simple procedures that will extend the life of your tubes and save you $$! The first step is recognizing any tube-related issues your amp may have. Faulty tubes are the most common cause of amplifier problems. Bad tubes can cause a myriad of problems and can be easily resolved if you know what to look for.
If you have no sound, loss of power, hum, popping, squealing, even no tremolo, you may have a bad tube. Try tapping on the tubes with a pencil or chopstick to see if they are microphonic. If the tube is picking up the sound of your tapping, it needs to be replaced. If you see the tubes burning red hot, this is sign of a problem. It may be a bad tube, or it may something else causing the tube to run hot. We will discuss other possible solutions for this problem at a later date.
Resolving most of these issues can be very simple, as tubes are quite easy to change. Try swapping a questionable tube with a known good one of the same value and see if this makes the problem go away. It’s best to wait for the tubes to cool down before pulling them, but if you must do it on the fly, you can use a dry rag or insulated puller like the “Tube Glove” from Electro-Harmonix.
Sometimes, the tube retaining clips (see photo on left) make the power tubes difficult to remove. I like to take a pair of pliers with insulated handles and hold them upside down, using the handles to press down on the metal retaining clip. This forces the retaining clip down and away from the fragile tube base. (see photo on right)
Then carefully remove the tube from the socket with your other hand. Of course, it’s safer to have your amp turned off or unplugged when doing this. Once you have the tube removed, check the socket for “arcing” or burned traces that actually cause the pins of the tube to connect with one another, causing tube malfunction. Sometimes this is caused by contamination on the socket, so make sure your sockets are clean and residue free. In extreme cases of arcing, the socket may need to be replaced. Also, make sure the socket pin connection is not loose. This does happen over time and with frequent tube changes. If the connections are loose, simply take a small-bladed screwdriver and force the contacts together a little bit to make a tighter hold.
Finally, here are some basic procedures that you should get in the habit of performing:
Use Your Standby Switch
When first turning on your amp, wait a minimum of 10 seconds before switching it from Standby mode to Play mode. This allows the tubes to warm up properly and will prevent premature wear and tear.
If you are taking a break, between sets for instance, be sure to put your amp back in Standby mode. This will also save wear and tear on the tubes.
Let ‘em Cool Down
After you are finished using your amp and have turned it off, let it cool down for at least five minutes before moving it. The tubes are very fragile when hot and any bump or jolt can cause damage to them.
By following these simple guidelines, you should be able to get much more value and enjoyment from your tube amp.