The sound of a blown speaker is pretty tell-tale - fuzzy, distorted crunchy sound that may be roughly reproducing the signal you are sending through it or making no sound at all.

There are a few scenarios that can cause a speaker to malfunction. A speaker can sustain physical damage to the cone or even the voice coil. Sometimes the damage is obvious. In other cases, the speaker may look fine, and the distortion may be so subtle that you could be wondering if your amplifier is actually at fault. In this article, we’ll share our tips on how to determine whether your speaker or your amp is to blame.

The pilot light in all Wurlitzer 120 Electronic Pianos is unique. You may notice that when you turn on your 120 the lamp takes a few extra seconds to turn on. Likewise, when turning the amp off the pilot light may take a few seconds to turn off. It kind of does its own thing. That is because the pilot light (or lamp) is a neon glow lamp. Just when you thought the 120 couldn’t get any cooler, it has its very own neon sign to let you know when its on.

All speakers have an impedance, usually 4 Ω, 8 Ω, or 16 Ω. For the best performance, you should match the impedance of your speakers to the output impedance of your amplifier. When the impedances match, the amp achieves the most efficient power transfer between the speaker and the amplifier. Power transfer, expressed in watts, affects the volume, drive, and overall sound quality of the amplifier.

All tubes follow the same basic principles. Inside a tube’s glass enclosure, you have 1) a vacuum and 2) at least two electrodes (but often more, depending on what type of tube we’re talking about). Each electrode has a specific job: either releasing electrons, attracting electrons, or slowing down or speeding up the flow of electrons. We’ll talk about these jobs later. For now, the main thing that tubes are intended to direct electrical current from A to B in some way that is useful to the circuit.

Cathode bypass capacitors are not absolutely necessary in a circuit. However, their presence or absence in an amplifier affects three things: gain, frequency response, and hum.

If you feel that your amp is lacking in any of these aspects, determining whether the cathodes are bypassed is a good place to start.

Carbon composition resistors are those brown cylindrical resistors that you’ll see in most amps made before 1970. All resistors produce Johnson (thermal) noise, a byproduct of the fact that resistors dissipate heat. However, depending in their material composition and shape, resistors may produce other types of noise as well. Carbon composition resistors produce the most noise. But is this really a bad thing? Yes and no.

There was a time when vacuum tubes were a huge industry. Just about every time of consumer electronics required tubes, and manufacturers competed for a slice of the pie by offering greater resiliency, lower noise, longer lifespans, etc. And then cheap silicon transistors were invented.

We removed these switches from a Wurlitzer 726 electronic piano. This model was the student version of the 720 (itself the console version of the 140b). One switch was for toggling between "self" and "ensemble" modes, while the other switched between the built-in speaker and the hardwired headphones.

We have a few Wurlitzer 200 circuit boards that we use for parts. Most of repairing vintage equipment is maintaining a large hoard. Just because a component is obsolete doesn't mean it's useless: a lot of old transistors and diodes are both absolutely necessary and hard to source. We do our best to keep a surplus when possible. 

We removed these vintage tubes from a Gretsch 6159 amplifier. Look for the listing soon!