How Often To Replace Tubes in Blues Jr

One of the most trouble thing about tube amps is the need to replace when them when they get burn out.

This article will inform you of the factors that determine the speed of the frequency as well as providing tutorials on how to replace tubes safely and efficiently.

On average, the average time to replace tubes in Fender Blues Jr is around 6 months to two years. Some can even last 10 years if they are well taken care of. The actual frequency depends on how often you played it and the length of each session. These tubes need to be replaced frequently due to the heat generated but that can be modded away if you know how.


Factors that influence tube replacement frequency in Fender Blue Jr

In general, these are the factors

  • Frequency of usage: this is the most important factor. Interesting, the intensity you are playing does not really affect the replacement rate. This is because the tubes are already in heated form so even if you push it harder, it wouldn’t increase the heat generated.
  • How you transport the amp: If you are moving the amp around frequently, it will affect the tube placement, especially if they got bounce around in a car or have toppled. In worse case scenario, the tube can even be shattered by poor
  • The bias setting: The default bias setting in Fender Blue tend to be higher, thus leading to faster burn out rate. Read below for more info.

Why Fender Blue Jr tubes get burn out

The reason is due to the Fender amps being biased very hot.

An amp bias setting affects the amount of current flow when the amp is idling. In order to avoid the ‘cold start’ problem, some manufacturers like Fender keeps the bias high. When it is hot for a long periods of time, the tube gets worn out faster.

To improve the life span of the tubes, you need to bring the bias setting down. Unfortunately, the Fender blues is a non adjustable bias amp. The setting at done at the factory and you can’t change it at will.

The only way to bring down the bias is to remove the current resistor and replacing it. This is not easy and I suggest you let professionals to do it for you.

At the default setting, your tubes will experience 95% power dissipation when idle. This is very high. You should aim for around 60-70% power dissipation after going through the modification process.


How to change tubes in blues junior

Changing the tubes out is pretty standard but be beware the amp contains enough voltage to kill! Do not touch the main body if you do not know what you are doing. I will mark out the areas below on where you should focus on.

Step 1: Unscrew the main board

Step 2: Familarize with the Blues Jr tubes layout within the amp.

Stay away from the top row!!! As mentioned above, there is enough voltage within an amp to kill a person so don’t touch any of these if you have no idea what you are doing. Instead, focus on the lower half of the board.

You will see 5 light bulb looking things at the bottom row. These are the tubes. They are arrange in a sequential manner, starting from right to left. At this stage, you can also check to see if any tubes have cracked. A cracked tube will definite the audio quality signficantly.

Step 3: If you want to remove, say tubes V4 and V5, you need to first unhook remove the mini stand that the last 2 tubes are ‘sitting on’. This can be undone by unhook 2 thin stick from the hole in the mini stand. The first one is obvious as you can see it at the front. The second one is at the back so you need to reach the unhook the stick.

Step 4: Once the ‘stand’ has been unhook, you can unscrew the tubes out. Simply hold the top of the tube and unplug them from their place holder.

Step 5: Insert the new tubes into the empty slots. If you have no idea what kind of replacement tubes to use, please read this article on the best tube for Fender Blues Jr.

It will tell you more information on which tube change will give you more impact on the tone quality. It will also recommend different tube brand options that cater to different audio preference.

Step 6: Once you have replaces the desired number of tubes, screw the cover back on and you are done. This whole process is pretty straight forward and shouldn’t take you more than 30 mins even if you are a beginner.



Changing tubes is one of the more common ‘mods’ one might need to do. I know people who do need to do anything to their amp even after 10 years of usage. Most, however, will probably need to change due to accidents, over heating or want a change in tone quality.

Regardless of the reasons, changing tubes is not a difficult chore. I hope my step by step tutorial on how to change tubes in Fender Blue Hr will give you sufficient help in your DIY efforts.

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