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Why do tubes in guitar amplifiers fail

When home stereo or amplifier stops functioning properly, you want it back in good shape in no time, but first things first. You must understand the components of the amplifier and how it works before you can figure out what could go wrong with it and how to fix its problems. The complexity of an amplifier repair usually depends on its parts that have a malfunction and their location in the unit. Before you learn how to repair amplifiers, you must brace yourself to delve into the wealth of information about its operations.


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WATCH RELATED VIDEO: amp tubes dying

Debunking Common Tube Amp Myths


User Name Remember Me? What is the HT fuse for on a tube amp? Tried with 3x new HT fuses. Each one blows immediately upon power up.

Any shared knowledge on a possible cause will be much appreciated. When the HT fuse fails, lots of people think "it's just a bad fuse That's not how fuses work though. The fact it failed indicates something needs to be addressed. That fuse is in line with the high voltage part of the circuit, and its failure is most often associated with a failing output tube.

You need to change the output tubes, put a new fuse in, and bias the amp. Even if "the tubes look good" Also "but it sounded fine right up until the first fuse blew" doesn't count either. Things always work right until they don't. I've heard this many times so I'm not poking fun at you. Once you do this and the amp works correctly, dispose of the old tubes; don't keep them around "as spares".

That might sound obvious but I've caught people doing it, reusing the tubes, and having the same problems as before then blaming me for it somehow. Don't put yourself in that spot. It sucks that "perfectly fine looking tubes" fail and you need to throw them away, but that's life.

There's nothing else even worth mentioning to check, that's how likely it is that it's the output tubes. Preamp tubes usually won't draw enough current even when they fail to blow the HT fuse. Of course if an output tube is causing the fuses to fail, there's the possibility of more damage, but it would most likely be something common such as a failed screen grid resistor on an output tube socket.

Depending on the amp, it might not require biasing. Which amp is it? Originally Posted by JamesPeters. There are 2 things you should now do, if you plan to keep running it like that: 1 Choose current ratings for HT and mains fuses that are half what they normally are. Using half the output tubes cuts the current draw of the amp roughly in half preamp tubes do draw some current but the most of it is for the output tubes. If you use the normal values of fuses while only running half the output tubes, you're risking more potential damage to the amp if those tubes fail since the fuses won't fail until they're handling twice the current they should under the "half power" condition.

It's not a huge risk, but it's worth doing especially since fuses are cheap. That is: hook a 16 ohm cabinet up to the amp's 8 ohm output for example.

This will provide a closer impedance match when running half the output tubes. The amp was designed with a transformer matching 4 output tubes to a load. Running it with 2 tubes changes things. Doubling the impedance like that compensates for this. It'll sound more normal and be safer in general.

Also make note of which output tube sockets you aren't currently using sitting vacant. If a problem occurs later when you use a matched quad of output tubes again, it's likely one of those 2 sockets has a failed screen grid resistor. Making a note of this now is a good idea.

It's easy enough to test for, but it can't hurt to make a note of it. Originally Posted by Geoff Waddington. Has true bias supply with trim, might want to touch that up. I'd use 2. Be sure to use the same type, which I assume is a slow-acting variety. If you're having trouble finding fuses locally you can order them from a place like mouser. If the bias was set fine before, it won't need any adjusting now. The decrease in current draw due to using fewer tubes will slightly increase the plate voltage since there's less load on the power transformer , but adjusting the bias to compensate isn't necessary.

It can't hurt to check the bias, but if you are not capable of checking the bias or biasing the amplifier without taking it to a tech, I wouldn't say this is an important thing to do.

As long as the amp works fine the way you have it now and it sounds fine. Besides, the way most people think about adjusting bias is a bit flawed. People will tend to pop a number into a calculation to figure out what they think the optimal bias point is. That's okay as a starting point but the truth is there's a range which makes sense to use and it is fairly subjective at that. When Geoff was talking about the output taps, he was referring to the wires that come off the secondary of the output transformer.

It is something that is relatively invisible to you because you're not inside the amp, so don't worry about it. He was just confirming that the amp is capable of being set for different impedances. Glad to help. Thread Tools. All times are GMT The time now is AM. User Name. Remember Me? Mark Forums Read. Send a private message to talustalus. Find More Posts by talustalus. Send a private message to JamesPeters.

Find More Posts by JamesPeters. Thank you very much for the info. Quote: Originally Posted by JamesPeters There are 2 things you should now do, if you plan to keep running it like that: 1 Choose current ratings for HT and mains fuses that are half what they normally are. Originally Posted by JamesPeters 2 Double the impedance. Originally Posted by JamesPeters Also make note of which output tube sockets you aren't currently using sitting vacant.

Send a private message to Geoff Waddington. Find More Posts by Geoff Waddington. Quote: Originally Posted by Geoff Waddington -- 3 taps on output secondary, so you are likely good to go there. Posting Rules.


Amplitudes: The Mesa Boogie Blog

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Repairs of all brands of tube and valve amps, tube replacements. Aside from the tubes there are other parts that can fail inside a guitar amplifier such.

Tube sound


Loyalty Points. What are points worth? Points are worth a 1p discount for every point you redeem. How many points will I earn when I shop? We display the number of points available for a product on the product's page on our website. Normally we'll give you one point for every pound you spend, but watch out for double and triple points deals for even more savings! Guaranteed Christmas delivery for in-stock items before 12pm 23rd December. Extended Christmas returns - Find out more. When searching for a new amp you may have heard the word rectifier come up, particularly with Mesa Boogie's Rectifier series.

Gui­tar Amp Tubes

why do tubes in guitar amplifiers fail

Typically the only tubes you may need to replace in the near term are the power tubes. If the amp is currently performing well, then no tube replacement is necessary. The preamp tubes tend to last for many years and only need to be replaced if they exhibit any signs of failure. Tubes are very easy to change out but there are a couple of things you have to pay attention to so as not to damage the tubes or the tube sockets when removing and replacing them. While we generally encourage players to experiment with different tubes, it is recommended to only use replacement tubes similar to what was installed by Two-Rock.

The problem is, not many of us have the luxury to a tube tester, leaving us in the dark with our amps diagnosis and treatment.

How to Diagnose Your Amps Bad Tube


JavaScript seems to be disabled in your browser. For the best experience on our site, be sure to turn on Javascript in your browser. To keep your tube amplifier running at its best, it needs proper care and maintenance. One of the most common sources of trouble when it comes to these kinds of amps is tube problems. In this article, we take a look at few common problems, how to spot them, and how to tell when its time to replace your bulbs.

Get Rolling: 5 Dos and Don'ts for Transporting Your Amp

Small W amps have become very popular in recent years. They are fun items but some seem more like toys than real amplifiers. Palmers approach with the EINS was to design a serious true tube amplifier for professional purposes. The speaker simulated output allows you to connect the output of the amp directly to your audio interface. Thanks to the integrated loadbox a speaker does not need to be connected. This way the EINS can be power boosted or used as a preamp or even on your pedalboard.

Pre amp tubes will generally last much longer than power tubes. amplifiers there is the fail safe fuse which is built in to indicate power tube failure.

What is Tube Bias? Why Do I Need to Bias New Power Tubes?

We are passionate about vintage amplifiers, and our service work is always performed with the purpose of safety and reliability, while maintaining as much of the amplifier's originality as possible. Service is available on most makes and models of guitar amplifiers, tube or solid state. We collect this non-refundable deposit when you drop off your amplifier.

Fault finding in audio equipment

RELATED VIDEO: How long do tubes last?

Question: What is a vacuum tube? Answer: A vacuum tube is an electronic device consisting of a minimum of four active elements: a heater filament , a cathode, a grid and a plate, all sealed in a vacuum glass enclosure to prevent parts from burning. Once heated, the cathode begins to emit electrons, which flow from the cathode which is negatively charged toward the plate which is positively charged. Question: What is a JAN tube? These are tubes that have been manufactured to a military specification or have been specifically selected for a military application. These tubes were either ruggedized during manufacture or selected from a very tight specification for highest performance and reliability.

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How To Tell If Your Tube Is Bad

Javascript is disabled on your browser. To view this site, you must enable JavaScript or upgrade to a JavaScript-capable browser. Written by Andy Johnson. In the world of tube amps, it seems like any number of issues can arise. However, there are a few broad problems that will occur in just about any amp at one point or another. These are problems that almost every tube amp owner has encountered over time: Tubes not lighting up, fuse s blowing, and bad ground connections. The web has a limitless supply of recommendations and schematics for you to review before you start your troubleshooting adventure.

Make sure your amp remains in great condition when traveling from gig to gig. As sturdy as many guitar and bass amplifiers are, many of them—especially tube amps—house fairly delicate electronics, and care must therefore be taken when transporting them. Transport the amp upright. Amp heads are especially easy to transport in their normal upright position.




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