TUBE NOISE & MICROPHONICS You may occasionally experience some form of tube noise or microphonics. Certainly no cause for alarm, this quirky behavior comes with the territory and the Tone. Much like changing a light bulb, you don’t need a technician to cure these types of minor user serviceable annoyances and in fact, you’ll be amazed at how easy it is to cure tube problems...by simply swapping out a pre-amp or power tube!

First may we suggest that you set the amplifier up on something so that you can get to the tubes comfortably without having to bend down. It also helps to have adequate lighting as you will need to see the tube sockets clearly to swap tubes. Use caution and common sense when touching the tubes after the amplifier has been on as they may be extremely hot! If they are hot and you don’t want to wait for them to cool off, try grasping them with a rag and also note that the glass down around the bulbous silvery tip is considerably less hot which makes it easier to handle. Gently rock the tube back and forth as you pull it away from its socket.

DIAGNOSING POWER TUBE FAILURES: There are two main types of tube faults: shorts and noise. Both large and small tubes may fall prey to either of these problems but diagnosis and remedy is usually simple.

If a fuse blows, the problem is most likely a shorted power tube and shorts can either be mild or severe. In a mildly shorted tube the electron flow has overcome the control grid and excess current flows to the plate. You will usually hear the amp become distorted and begin to hum slightly. If this occurs, quickly look at the power tubes as you switch the amp to STANDBY and try to identify one as glowing red hot. It is likely that two of a pair will be glowing since the “shorted” tube will pull down the bias for its adjacent mates, but one tube may be glowing hotter — and that one is the culprit. The other two are often fine — unless they’ve been glowing bright red for several minutes.

Because there is no physical short inside the tube (just electrons rioting out of control) merely switching to STANDBY for a few moments then back to ON will usually cure the problem...at least temporarily. Watch the tubes carefully now. Should the problem recur, the intermit- tent tube will visibly start to over heat before the others and thus it can be identified. It should be replaced with one from the same color batch, shown on its label. Call us and we will send one out to you.

The severe short is not nearly so benign. In the worst cases, a major arcing short occurs between the plate and the cathode with visible lightning inside the glass and a major noise through the speaker. If this is seen to happen, IMMEDIATELY turn the amp to STANDBY. By this time the fuse probably will have blown. Such a short is usually caused by a physical breakdown inside the tube including contaminate coming loose or physical contact (or near contact) between the elements. Replace it and the fuse with the proper slo-blo type and power up the amp using the power up procedure as we described earlier in this manual.

TUBE NOISE: Often caused by contamination within in a tube, the culprit can usually be identified, and by lightly tapping on the glass, you will probably hear the noise change. Hearing some noise through the speakers while tapping on the 12AX7’s is normal however. And the one nearer the INPUT will always sound louder because its output is being further amplified by the second 12AX7.

The power tubes should be all but quiet when they are tapped. If crackling or hissing changes with the tapping, you have probably found the problem. To confirm a noisy power tube, merely put the Nomad on Standby, remove it from its socket and turn it back on. It will cause no damage to run the Nomad briefly with one power tube missing. You may notice a slight background hum, however, as the push-pull becomes unbalanced. Whenever you are trying to diagnose a suspect tube, keep your other hand on the POWER and STANDBY switches ready to shut them off instantly in the unlikely case you provoke a major short.

If you think you’ve located a problem tube but aren’t sure, we recommend substituting the suspect with a new one just to be sure of your diagnoses. You will be doing yourself and us a big favor by just following the simple guidelines previously mentioned regarding tube replacement. You’ll probably be successful with much less effort than is required to disconnect everything and haul the unit to a technician who will basically perform the same simple tests. If the tubes are still within their six-month warranty period, we will happily send you a replacement. Just note the color designation on the tube label so that we can send you the appropriate match.

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Mesa/Boogie 100, 45, 55 owner manual
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45, 55, 100 specifications

Mesa/Boogie, a name synonymous with innovation in the guitar amplification world, has carved out a niche in the hearts of musicians with its formidable lineup of amplifiers. Among these, the Mark series stands out, particularly with models like the Mark 100, 55, and 45. Each model brings its unique flavor and versatility, allowing players to craft their sound with precision.

The Mesa/Boogie Mark 100 is a powerhouse in the 100-watt category. It boasts multiple channels, allowing guitarists to switch between clean, crunchy, and high-gain tones effortlessly. One of its standout features is the onboard EQ, which facilitates fine-tuning for different guitars, pickups, and musical styles. The Mark 100 is engineered with Mesa's signature Dyna-Watt technology, providing a dynamic response at various volume levels without sacrificing tonal quality. This responsiveness makes it ideal for both live performance and studio recording, as it yields rich harmonic overtones and a wide dynamic range.

Moving to the Mark 55, this model offers a refined approach with 55 watts of power. It retains many features present in the Mark 100 but is more accessible for players who prefer a slightly lower wattage. The Mark 55 excels in mid-gain settings and is popular among blues and rock guitarists. Its Dual Rectifier circuitry can dial in everything from smooth, bluesy overdrive to tight, aggressive rock tones. The amp also incorporates a versatile effects loop, providing seamless integration with pedals and processors, making it a favorite among pedal enthusiasts.

The Mark 45, perhaps the most compact of the trio, brings 45 watts of power to the table, making it a versatile choice for players seeking portability without compromising tone. It retains critical features such as multiple channels and a powerful EQ section while being lighter and easier to transport. The Mark 45's sweet spot is found in its ability to deliver rich, saturated tones at manageable volume levels. Often favored for intimate gigs and home recordings, its versatility allows players to explore genres from jazz to metal with equal flair.

All three Mesa/Boogie amplifiers utilize high-quality components designed for durability and peak performance. Their construction is robust, ensuring reliability on stage or in the studio. With advanced features such as power scaling and tube rectification options, musicians can tailor their sound precisely.

In summary, the Mesa/Boogie Mark 100, 55, and 45 each present guitarists with distinctive tonal characteristics and features that enhance playability and sound. From the powerful performance of the 100 to the compact yet versatile 45, these amplifiers deliver the high-quality, rich tones that Mesa/Boogie is renowned for, catering to the diverse needs of players across genres.
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