Did you know that the transformers and chokes in your amps are aging? If your amp is 20 years or older you really need to know this. Over time, the materials that were used in the construction of these transformers have changed -- actually degraded, and become increasingly fragile. Before the "smoke gets in your eyes" hang on to your power cord and don't plug in just yet until you understand the following.
Basically, transformers can be broken down into three components. The first being "copper," which is what the wound coils inside and the lead wires are made of. The second is "steel" which is what the stack of metal plates in the core are made from. Third, and most important to overall life expectancy, is "insulation" whose function is to keep things alive and running properly by not letting the other components touch each other and/or conduct when they are not supposed to. A breakdown with any one of these components will eventually grenade your amp!
Copper by itself doesn't really age, but the thin, clear coating of insulation around it does in the form of microscopic spider web cracking. This will lead to high voltage break down in the winding. Lead wires are also susceptible when their vinyl or cloth jackets become old and brittle -- sometimes causing arcing through the cracks and splits in the insulation. Phantom clicks and pops heard through the speaker are also telltale symptoms of aging.
Steel can degrade over time and extended use, especially if contains traces carbon. Carbon is a contaminant and has no positive contribution towards tone. The older the amp is, the higher the possibility. When that happens, the core begins to be less conductive to magnetism (magnetism is the essence of how transformers work!). Symptoms of that occurring include higher transformer operating temperatures, general dulling out of tone with the absence of treble frequencies, fuzzy mids, and a noticeable softening of the bass notes. None of which has anything to do with rust. Remember, rust on your core is a helping friend.
Insulation is where most of the aging problems lie. The older your amp is, the more likely its transformers were wound on paper tube bobbins -- with Kraft paper as its insulation (which is no different than the paper used to make shopping bags at your local grocery store). This material has a tendency to suck up moisture and retain it. Moisture alters the delicate balance of reactive values in the transformer throwing off your tone into less interesting domains. The more destructive side to this moisture absorption is that it harbors mold and bacteria which consumes the paper, further diminishing its insulating properties. Even if this material has avoided moisture altogether, it will eventually crumble into dust over time.
Are all vintage amps time bombs? Certainly not. But to be safe don't play Russian Roulette with your valuable, irreplaceable, and highly-prized collectible vintage amps. If your amp hasn't been fired up in years, don't just plug it in and flick that switch on. You risk seeing your investment go up in smoke.
If you are in possession of a Variac, a volt meter and a current meter then you have the necessary tools to properly and carefully ramp up the input voltage while monitoring the current draw. This will also help reform the filter caps as well as avoid the "smoke test" with your transformers. If you don't know what any of this means then we strongly recommend getting an amp tech to do it for you. If you don't know of one, call us and we’ll help you find one qualified to do the job. When the fuses in your amp keep blowing it is your amp's way of telling you something's wrong and to take it to a professional.
