Our columnist’s beloved Fender Super Reverb head goes under the knife.
Vintage Fenders are some of the best-sounding amplifiers around, but from time to time, they need a bit of love to give up the goods. Here are the top issues you’ll encounter with your black- and silver-panel Fender amps, and how to fix them.
Trouble and worrying are part of a vintage tube amp owner’s life. In this article, I will try to teach some basic troubleshooting for vintage Fender amps. It will only require a little practice, patience, and, most importantly, curiosity, which to me is the single most important skill in life—we can accomplish great things by reading, seeking advice, trying, failing, and not giving up. So, let’s start!
As usual, I will refer to the silver- and black-panel Fender amps, but everything is applicable to earlier amps as well. I will often refer to tubes: On a Deluxe Reverb, for example, the tubes are referred to from V1 to V9. Always consult your amplifier’s schematic to confirm these placements.
No Reverb
The reverb tank is the most delicate component of these amps. The springs, wires, and soldering joints are thin and weak, and the reverb cables and plugs are also easily damaged, as they are exposed on the backside of the chassis.
First, check the plugs on both the amp and reverb tank. Unplug and switch the input and output to see if the previous player made a mistake. Often, the plugs are damaged and not conducting current, or the inner wire or outer insulation are broken. I recommend replacing old cables with new, vintage-correct ones if you suspect the slightest cable or plug issue.
“Trouble and worrying are part of a vintage-tube-amp owner’s life.”
A bad V3 or V4 preamp tube may also cause reverb loss. If replacing tubes or reverb cables does not help, you should try hooking up another amp’s reverb tank to verify whether you have an amp or reverb tank issue. The reverb springs may also have jumped out of position and need to be re-attached. I recommend refreshing soldering joints here.
No Vibrato
First, the footswitch must be plugged in for the vibrato to work. If you don’t have one or suspect that it’s malfunctioning, you can either buy or make yourself an “always-on” phono plug that is shorted internally with solder. A bad vibrato-driver tube may also cause vibrato loss, which is fixed easily by replacing the V5 with another 12AX7. If none of this helps, a tech should open the amp and inspect the vibrato tube circuitry, and/or replace the opto-oscillator component.
Blown Fuse
Pull all the tubes before replacing a blown fuse. If the fuse blows repeatedly without any tubes installed, a tech should be involved for inspecting the filter caps/resistors, power transformer, and the high-wattage resistors on the power-tube socket pins.
If the pilot lamp light is on when all tubes are pulled out, start inserting tubes one by one from the V1 rectifier tube. Turn power/standby on. If the fuse blows, the rectifier tube is bad. Then, insert both power tubes and turn power/standby on. If the fuse blows, you need new power tubes, and possibly new screen and plate resistors. Continue this procedure for each of the preamp tubes until you identify corrupted tubes that draw too much current.
Weak Tone
Check speaker cable(s) and speaker terminals. I find it useful to connect to a second amp’s speakers to determine if it’s the speakers or an amp that is the problem. (Remember to turn off or set the amp in standby whenever speakers are disconnected.)
Then, verify that the tubes are working by following the previous “blown fuse” procedure. Look for loose power-tube sockets causing bad connections by gently pushing them around in the socket. If speakers, tubes, and sockets are working fine, a tech should further inspect the amp.
Distortion, Reduced Volume, or Weak Bass
When playing powerful 40-watt amps at low volume, it can be difficult to hear if only one tube is working. If one of the power tubes is malfunctioning, you will experience distortion and farty bass. Non-matching power tubes can also result in distortion and reduced clean headroom, which is detected by measuring with a bias meter.
Preamp tubes in wrong positions may also affect volume response and cause an amp to distort too early or too late. Check all tubes and replace them one by one with fresh ones as you listen for tone changes. Sometimes we prefer the wrong tubes because we like more distortion. (My tube strategy is to replace tubes only when they fail entirely. I don’t mind weaker power, rectifier, or phase-inverter tubes since these amps are more than loud enough.)
Rattling Noise
Loose screws and nuts can cause rattling noise and should be inspected and tightened regularly, including on the chassis, baffle board, tilt-back legs, speaker, handle, and anywhere else. If the baffle board is warped and worn so that the screws are not tight, I never hesitate to install a new, solid-pine baffle. This usually improves tone and robustness compared to old, warped MDF baffles
Our columnist is back to balance the force with a look at the top qualities of old-school Fullerton noise-makers.
Last year, I wrote a column listing the top 10 annoying things about vintage Fender amps. Now, I seek to rebalance the equation, and will share my list of reasons to love them.
There are countless reasons why simple, vintage Fender amps are still the tool of choice for many working musicians, both onstage and in the studio. I suppose my list is also colored by the fact that I am an electrical engineer, just as Leo Fender was. I have traded and serviced them for almost three decades. As usual, I will mostly refer to the black-panel and silver-panel era of amps from the 1960s and ’70s.
1. Circuit standardization
The amp techs among us may have noticed how similar the electrical circuits are in the various Fender models, especially the popular black-panel Deluxe, Vibrolux, Pro, Vibroverb, Super, Twin, and Showman. Many of us use the nickname “AB763” amps because they are based on the same electrical circuit design, and some are almost identical on the inside. Yes, there are some differences, but apart from the power levels and size, they follow the exact same recipe with the tube layout, preamp section with tone stack, the long-tail phase inverter, the class-AB push-pull power tube design, fixed bias, negative feedback loop, and so on.
So, the tonal differences between the black- and silver-panel-era amps are explained by cabinet size, speaker configurations, speaker type, and power levels. Once you learn how to work on one model, you can work on them all.
2. Circuit simplicity
The first time I opened a Fender amp and inspected its innards was in 1998 when I got my first vintage one, a 1965 pre-CBS Super Reverb. I was surprised by how simple and organized the circuit was. The few components were laid out in patterns and functional sections, and the wires were cut in perfect lengths and bent nicely, tying everything together in a way that was easy to understand when I followed the circuit layout diagram. Simplicity means fewer things that can go wrong. These qualities also make maintenance easier for amateurs and enthusiasts.
3. Low-cost physical construction
Back in the day, Fender was concerned about cost and weight, and as a result, there was no high-end selection of materials or advanced mechanical features. If you need to repair or rebuild something, you don’t have to rebuild with absolute vintage correctness to obtain the original Fender tone. If, for example, an MDF baffle board is damaged, which tends to happen to amps with multiple heavy speakers, I always use thicker pine plywood when cutting out a new board. The tone remains pretty much the same, while robustness is drastically improved. This also goes for cabinet pieces, back plates, screws, and nuts. Do what Fender did, and use what you have available.
4. Tube mods
As a player, I like simple tube-swap mods, and as an engineer, I am impressed at how vintage Fender amps handle different tubes, or even allow you to pull some tubes out. Did you know that you can remove V2, V3, V4, and V5 in an AB763 amp, and the normal channel will still work?
My favorite tube swaps are a 12AX7 in the phase-inverter position for less headroom; a 12AU7 as a reverb driver for better reverb control; 6L6s in place of 6V6s in the Deluxe Reverb for cleaner headroom; and a single 6L6 in the Princeton Reverb for less headroom. There are plenty other tube swaps that you can learn about on my website, fenderguru.com, or in previous articles here at Premier Guitar. You risk malfunction and burned tubes and components if you insert the wrong tubes, so be careful and trust only valid sources.
5. The big lineup
In my list of problems with Fender amps, I pointed out a few amps that I would have recommended that Leo Fender cut out to reduce production complexity and cut costs. However, I do dig the big lineup of different amp models, from small practice amps to huge stage amps. You can pick the exact tool according to your taste and needs, and as mentioned earlier, all of them share the characteristic Fender clean tone—it’s just that some are much louder than others.
6. The clean tone
For me, the clean tone of an amp is everything. This is my number-one reason why I love the old-school Fender amps. They were designed as clean, natural tone platforms, for the simple purpose of amplifying the sound of your guitar, bass, or keyboard.
But a proper analysis of Fender’s clean tone requires a column of its own, so stay tuned for the next Silver and Black!
The author’s Collings D2H rests on his favorite Fender amp combination for acoustic guitar: a Bandmaster Reverb atop a 1x12 extension cab with an Eminence Maverick inside. The amp has a custom-made baffle board with two 8" speakers, so can go it alone for smaller gigs.
Interested in plugging a flattop into your favorite silver- or black-panel beauty? Here’s what you need to know.
Have you ever tried to plug your acoustic guitar into a classic-style Fender amp? There are some hurdles to overcome, and this month I’ll provide some advice on how to get past them. But first, some background.
Amps made for electric guitars are carefully designed and matched to the voltages and frequency profiles of signals delivered by electromagnetic pickups. An amp sounds best when it does a good job at amplifying or filtering out certain frequencies. So many of us have stumbled upon challenges when the input signal—say from an acoustic guitar or other instrument—is way different than what the amp expects.
A guitar signal is initially created by moving the strings. The more vibrating metal mass closer to the pickup’s magnet, the more magnetic pull and more current is induced inside the coil wire in the pickups. More windings and stronger magnets induce more current, but also reduce brightness and clarity. The coil-wire thickness, wire material, and coating material and thickness also play a role in signal strength and frequency response. The signal voltage produced by a pickup is low—typically between 0.1 and 1V—and contains frequencies between 80 and 1200 Hz.
On the amp side, there are even more factors that amplify or weaken certain frequencies—so-called frequency filtering. Take a vintage Fender Deluxe Reverb. It is designed with specific tubes, resistors, and caps in the preamp stage to amplify a weak input signal and shape it through EQ, mix in some reverb, and transport the result to the power amp circuit, which does three things. First, it splits and duplicates that result into an inverted signal, then it amplifies the two signals as much as possible, and then feeds them into each side of a power transformer that alters the resulting voltage to a suitable level for a loudspeaker. That’s typically 30 to 50V. The speaker cabinet and loudspeaker itself are the final stage in delivering a filtered and amplified guitar tone.
For acoustic guitars I prefer modern American-style speakers that can handle high power and both a firm bass response and a crisp top end.
If you hook up other instruments, like an acoustic guitar or a harmonica with a microphone, and feed an electric guitar amp their signals, you will get totally different results throughout the circuit. You may not get the tone you expect, or, in the worst case, you might damage the amp. But generally, all passive sources with electromagnetic coil pickups are safe to use. This includes piezo pickups mounted to the bridge of an acoustic guitar and vocal microphones. Since they are not powered by an external source like a 9V battery, they are passive and create a weak signal.
You should be careful using electrically powered sources like an acoustic guitar with a battery-powered preamp and EQ. Also, electric pianos, synthesizers, or Bluetooth speakers with mini-jack outputs are dangerous, too, since they can easily blow the loudspeakers due to a wrong volume or EQ setting. Electric pianos can sound very good through a vintage Fender amp. I’ve seen Fender Rhodes keyboards played through Twin Reverbs, and we’ve all heard organs through Leslie/Vibratone speakers, which can be run by Fender guitar amps.
Acoustic guitars with active pickups can be difficult. With typical default amp settings for electric guitar, the tone is narrow and focused around certain mid frequencies. It lacks fullness, top-end clarity, and overall balance. So, I have some tricks you should try if you’re experimenting with this option. First, set all the EQ knobs to 10. This allows the guitar signal to travel through the preamp section with minimum change of tone. Be very careful with volume and start low—at around 1.5—and increase from there. I find big, powerful Fender amps are best for this, since they have plenty of clean headroom and wide EQ possibilities with a full set of bass, mid, treble, and bright-switch controls. And that makes them less prone to howling feedback.
A big speaker cabinet will enhance the low end, allowing the preamp and power amp to relax more without maxing out clean headroom. Remember that the power and energy lie in the bass. I suggest the silver-panel 40-watt Bandmaster Reverb and 85-watt Showman Reverb as practical amp heads for acoustic purposes. I use my Bandmaster Reverb with a 1x12 extension cabinet loaded with an Eminence Maverick. For acoustic guitars, I prefer modern American-style speakers that can handle high power and both a firm bass response and a crisp top end. Speakers are very important for your tone. The guitar’s pickups are also important, together with a correct setup, so the action permits the optimum proximity of the pickups.
Acoustic pickups don’t have to be expensive. They just need to be balanced and clear. A good guitar amp and some careful adjustments of the controls will do the rest.
