Triodes are tubes which can be used in amplifiers, computers, radio receivers and transmitters and other things. Triodes were later replaced by transistors.

The first electronic device ever invented is the relay, a remote switch controlled by electricity that was invented in 1835 by Joseph Henry, an American scientist, although it is also claimed that the English inventor Edward Davy “certainly invented the electric relay” in his electric telegraph.

A vacuum tube, an electron tube, valve (British usage) or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. Electrons can only flow in one direction through the device—from the cathode to the anode.

All vacuum tube circuits operate at dangerous voltage levels. The 845SE and other powerful tube amplifiers operate at over 1000 volts. Accidental contact with an energized circuit of this nature would likely be instantly lethal.

Tube amps are expensive because they adopt pre and power tubes as their primary amplification source. Each tube costs roughly $50 and can have up to 4 of them within a single unit. Secondly, these amps have more expensive components, larger cases, and more complex circuitry than solid-state amps.

Does anyone still manufacture new vacuum tubes? The simple answer is yes if you are referring to the kind used in household radio and television sets, but don’t expect to find a full line of replacements. Also, don’t expect them to be made anywhere other than places like China and Russia.

When a vacuum tube develops an air leak (a small crack or bad seal by a pin for example) this getter color will change to pure white. If you see this you know with 100% certainty that the tube is bad. Third, look for a purple glow that is very focused around specific elements inside the tube.

Some older Western Electric tubes unused or the original box will sometimes sell for over a thousand dollars at auction. Any early vacuum tube with a “tip” (the little glass nub on the top) and a brass base has some value to collectors even if it’s just usable for display.

The age of your radio can contribute to its value: an early radio generally has more historical interest than a 1950s radio, but the value depends on many more factors. You can identify most radios by their model number, which can be found on the casing or stamped on a component of the radio on the inside.

Do note that not all vacuum tubes can be repaired or revived. Loose base, no connection at tube pin due to broken wire or cracked solder, or broken pin can be easily repaired by base replacement or re-connection internally at the base. Broken filament, could possibly be repaired, on case by case basis.

These are the most common signs that tubes need replacement.

1. Excessive noise (hiss, hum) including squealing or microphonic tubes.
2. Loss of high end. Little or no treble.
3. A muddy bottom end.
4. Erratic changes in the overall volume.
5. A blown H.T.
6. The amp doesn’t work!

You should replace them when they are dead. There is no set rule for how long they last, but in general, they last longer than power tubes. Maybe twice as long or better life expectancy for power tubes. They are also self-biasing of course, so don’t be afraid to change them yourself.

backline Tele-Afflicted. Preamp tubes have Much Smaller filaments and generally do not glow as brightly as the bigger power tubes. Different tubes are made differently, and some have their heaters obscured; so you do not hardly see them even when they are working properly.

You can expect a conventional amplifier tube to have a service life ranging up to 10,000 hours. Tubes with military specifications are built to last up to 100,000 hours.

Crackling, squeals and feedback, excessive noise and muddiness or low output are all evidence of tube problems. Power tubes. The two main symptoms of a power tube problem are a blown fuse or a tube that begins to glow cherry red. Either are typically indicative of a power tube failure.

Depending where you live, 12AX7s can be had for around $8-12. EL84 aren’t much more. If you just get run of the mill stuff it will be cheap. Once you start looking into NOS tubes, etc, you can expect to pay $25-200 per tube in some cases.

Member. I charge $30/hr + cost of parts, with a $50 minimum. Your problems could be simple, ie: pre-amp tubes, or more complex, a relay may need to be replaced. I’d charge 3-4 hours at least to take that amp apart and diagnose everything.

If you are going to spend money on biasing tubes just buy new tubes. Might make sense to do this with stock tubes in other amps. a lot of techs charge $25-50 USD to bais an amp.

If you changed to tubes with a lower resistance without biasing the amp you would quickly burn through those tubes and potentially damage the amp and yourself in the process. This is because the amp is still pushing out current at a higher level than the valves are able to take.

Unless your amp is cathode biased, yes, you need to have it biased when you change tubes and yes, you should periodically have that checked and adjusted as necessary. PAY ATTENTION TO THIS: Most amplifier have lethal voltage inside. So you should NEVER set or adjust bias if you do not know how to do it.

You can change tubes on a 900 easily.

At most Sam Ash Music Stores you will find a professionally staffed musical instrument service and repair center that can fix and maintain your instruments – regardless of if you purchased it from us or not.

every 3-6 months