In this article, we deal with a topic that is a common concern among users of car stereos. The amp turns on, but no sound is heard, even on increasing the volume. You may think that how to fix a blown amp is a highly technical solution which you won’t be able to do unless you are an electronics expert. Let us begin with this disclaimer. You cannot fix a blown amp unless you have some training in electronics. However, is your amp blown? Let me share a little anecdote with you.
My father was a highly-skilled electrical design engineer. He always used to fix broken appliances at home. Growing up with him, I also became a handyman of sorts. One day, we were looking at a faulty electric iron. On opening it, we could not detect a fault. After a lot of investigation, we discovered that there was just a loose connection in the mains plug. We needn’t have opened the iron in the first place – just reconnecting the cable in the plug using a screwdriver would have sufficed!
Keeping in mind the above incident, we can say that the same principle applies to several other electric and electronic appliances including amplifiers. You just need to follow some simple steps which we have outlined in this article.
Here is a list of items that you will need to undertake to troubleshoot for an amp not getting power or if the amp has power but no sound:
These are a few of the necessary tools that you are likely to use for fixing an amp not getting power. However, the list is not exhaustive, and you may find some additional tools that come in handy while performing your troubleshooting operations. It is a good idea to locate a suitable box in which to store all these items. You can get some nifty toolboxes from a hardware store, or you can shop for toolboxes online.
We have tried to generalize the steps for troubleshooting for fixing a blown amp. However, you will sometimes come across something unique that we have not described here. In such a case, just follow the general approach that we have outlined and use your instincts.
You also need to exercise good judgment to decide whether a job is within your capabilities or not. You may do better to get professional help. But like we said earlier, it could just be an underlying problem which you can fix yourself. So, here are the necessary steps that you need to follow:
A common occurrence is a loose connection to the plugs. Check all the input and output jacks. Check the main power supply and if it has a plug, check if the connection is OK.
Some wires run from the rear of your amplifier to your speakers. Ensure that there is no loose connection. Check cables for continuity through your multimeter.
Pro Tip: Disconnect all other audio sources leaving only the internal receiver connected. Now run the amp to find out if it has power or good sound.
Your amp will have one or more cartridge fuse. A cartridge fuse is a tiny glass tube with two metallic caps on either end of it. These caps are connected internally by a thin metallic filament.
If a fuse has blown, it will mean that the metallic filament has burnt out and you may or may not see carbon accumulation or oxide powder on the inside of the glass. You can remove the fuse and check it for continuity with your multimeter. Always replace the fuse with the same rating as the original one. We express fuse rating in milliamps (ma).
If your amplifier detects that there is something wrong with the circuitry, it may go into “protect mode” which you can observe by seeing the light that glows indicating protect mode. Protect mode is an inbuilt safety feature of your amp to avoid damage to internal components.
If your amplifier goes into protect mode, try disconnecting the speakers. If the protect mode light disappears once you do this, you can conclude that there is something wrong with the speakers. Check the speaker connections and if all seems OK, then try changing the speakers and rechecking the amp.
The amplifier may also go into protect mode if the grounding is insufficient, possibly due to faulty RCA cables. Just replace the existing RCA cables with good ones, and if the protect mode light goes out, you know that the problem lies in faulty RCA cables.
If all else fails, and your amp has power but no sound, unscrew the covers to expose the printed circuit board (PCB). Examine all the components carefully. If you notice a transistor, capacitor or resistor that seems to have burnt out, replace it and check the amplifier.
Check all solder points by gently pulling the components. If you notice some looseness, then melt the joint with your soldering iron, adding a touch of fresh solder and perhaps a bit of flux to re-establish the connection.
You can check each resistor with your multimeter. Set your multimeter to ‘resistance' or ‘ohms.' Now, power the amplifier and place the probes of your multimeter on either side of the resistor. The reading on your multimeter should show the corresponding measurement in ohms for the rating of the resistor within a 5% variation. If not, then the resistor needs to be replaced.
Pro Tip: If you are soldering components to the printed circuit board, ensure that your joints have a clean, shiny finish. If the surface is dull, you may have done a "dry solder" which can result in poor connectivity.
The output transformer is the transformer that supplies electrical energy to the speaker. Disconnect the output wires of the transformer and run the amplifier. Using your multimeter set to ‘DC volts,' measure the voltage that is coming out from the output wires.
If there is no voltage, the transformer has burnt, and you need to replace it. If there is an abnormally high voltage as compared to the required voltage specified in the manual, you have an open, leaking transformer, and you still have to change it.
Here is a unique tip which you will rarely come across. When you first open the cover of your amp, take photographs. Take close-ups of any parts that seem to be defective or burnt. Pay particular attention to the quality of your images and ensure that they are clear with the specifications of the components as legible as possible, including the amp’s model number, serial number, brand and so on.
Photographing your amp’s internals serves two purposes. Firstly, if you are going to dismantle any parts, it will help you re-assemble the amp later. Secondly, if you find that you are unable to fix it, you can send your photographs to an expert who will be able to help you out, especially if you have clear images with all the necessary details visible.
These are the necessary steps that you need to follow for troubleshooting if your amp has power but no sound or if your amp is not getting power at all. You may feel overwhelmed by some of the steps described here. However, do be advised that you only need to do as much as you feel comfortable in doing.
But, once you get into the heart of the matter and you get more and more involved in the job, you will see that with a little practice, you can do much more than you ever imagined yourself doing.
Some of the steps described here are a bit technical, and you may need to take the help of someone who has a bit more experience in these matters. However, as the adage goes, "Practice makes perfect." So, the more you do, the more confident you will become, and you will get better and better at how to fix a blown amp.
We hope you have enjoyed reading this article. Please don't hesitate to get back to us with your valuable feedback, comments, and questions and we will be happy to respond.
Here at Car Speaker Land we have only one goal: to bring you the best speakers around. Well, actually we have two goals: we also want to make sure that you’re able to get things going without having to pay the steep fees which are often charged for even the most basic procedures in auto shops.