I know this is an old topic and It's quite possible that someone else has started a new one somewhere. I stumbled onto this one while looking for parts for one of these Fender Frontman 15G amplifiers. I thought it might be useful for someone else who is having problems with this amplifier blowing fuses.
#1 - Do not defeat the fuse. It is there to protect you, the wiring, and other components in the amplifier. If you defeat it you will be looking for a hard to find transformer that is out of production. 16.4V on the secondary (output to the amplifier)
#2 Replacing random parts is a huge waste of money and time. As someone else has already stated earlier in this thread there is a process for diagnosing repairs. Always check the fuse first. Just because it appears good doesn't mean that it isn't blown. Use a multi-meter and test for continuity.
Okay, now that I got that out of they way. It is helpful to do a little homework before you begin any work for a products known issues. It can save you a lot of time and often someone else has already repaired the item many times and shared their knowledge. I found this to be the case with the Frontman 15G and other similar amplifiers.
Yes, many of you are right in your assumptions that the amplifiers are junk. They are poorly designed and have problems. Let's be honest here. Not too many of you are building amplifiers. It's pretty easy to say it's junk when you've had problems with it, but in honesty it can be a decent little practice amp for a great many people when treated kindly.
The most common failure with the amp is when using the headphone jacks or the external input from another device. The J-fet will fail and can often damage some parts around it. These are fairly cheap to buy by most standards and are easy to replace. Adding an external heat sink above and beyond the one Fender supplied with the amp can also extend this transistors life a great deal. Keeping the drive moderate (This includes using pedals at a reasonable level) will also go a long way to keep it running.
Who doesn't like distortion? I know it's all part of the fun and often part of the sound. Distortion damages speakers quicker than anything else. Keep this in mind when you've got it squealing and howling.
So, let's begin diagnosis. You should have already checked the fuse. If the fuse tests good you're headed in the right direction. If it doesn't replace it and sometimes you get lucky and you're back in business.
Fuse blows immediately? Well, that means you need to find out what is causing an overload condition. Something is drawing too much power (Likely that main power transistor / JFET that Fender put into the amplifier. Replacing the fuse again at this point is a waste of time. Meter the secondary on the main power transformer and see what the voltage is.
The Fender Frontman 15G should be between 12 - 18 volts. The transformer I have is rated at 16.4V. If you've got some voltage that's larger or smaller your amp likely won't work. You're going to be searching for that transformer for a while.
Transformer seems okay? Check the input voltage at the JFET and also the output voltages. Nothing huh? Replace the JFET it's a TDA2030 for the 15w or a TDA2050 for the 30w version. Replace it with one that matches your model.
Likely this will have your amp up and running.
As for buzzing in the amplifier. This is usually a grounding issue on the signal path. it can also be caused by poorly done solder work. Make sure that when you solder things that you use a heat sink and do not make cold solders. Check that there is no solder paths being made where you don't want them and always check your work before you apply any power.
#1 - Do not defeat the fuse. It is there to protect you, the wiring, and other components in the amplifier. If you defeat it you will be looking for a hard to find transformer that is out of production. 16.4V on the secondary (output to the amplifier)
#2 Replacing random parts is a huge waste of money and time. As someone else has already stated earlier in this thread there is a process for diagnosing repairs. Always check the fuse first. Just because it appears good doesn't mean that it isn't blown. Use a multi-meter and test for continuity.
Okay, now that I got that out of they way. It is helpful to do a little homework before you begin any work for a products known issues. It can save you a lot of time and often someone else has already repaired the item many times and shared their knowledge. I found this to be the case with the Frontman 15G and other similar amplifiers.
Yes, many of you are right in your assumptions that the amplifiers are junk. They are poorly designed and have problems. Let's be honest here. Not too many of you are building amplifiers. It's pretty easy to say it's junk when you've had problems with it, but in honesty it can be a decent little practice amp for a great many people when treated kindly.
The most common failure with the amp is when using the headphone jacks or the external input from another device. The J-fet will fail and can often damage some parts around it. These are fairly cheap to buy by most standards and are easy to replace. Adding an external heat sink above and beyond the one Fender supplied with the amp can also extend this transistors life a great deal. Keeping the drive moderate (This includes using pedals at a reasonable level) will also go a long way to keep it running.
Who doesn't like distortion? I know it's all part of the fun and often part of the sound. Distortion damages speakers quicker than anything else. Keep this in mind when you've got it squealing and howling.
So, let's begin diagnosis. You should have already checked the fuse. If the fuse tests good you're headed in the right direction. If it doesn't replace it and sometimes you get lucky and you're back in business.
Fuse blows immediately? Well, that means you need to find out what is causing an overload condition. Something is drawing too much power (Likely that main power transistor / JFET that Fender put into the amplifier. Replacing the fuse again at this point is a waste of time. Meter the secondary on the main power transformer and see what the voltage is.
The Fender Frontman 15G should be between 12 - 18 volts. The transformer I have is rated at 16.4V. If you've got some voltage that's larger or smaller your amp likely won't work. You're going to be searching for that transformer for a while.
Transformer seems okay? Check the input voltage at the JFET and also the output voltages. Nothing huh? Replace the JFET it's a TDA2030 for the 15w or a TDA2050 for the 30w version. Replace it with one that matches your model.
Likely this will have your amp up and running.
As for buzzing in the amplifier. This is usually a grounding issue on the signal path. it can also be caused by poorly done solder work. Make sure that when you solder things that you use a heat sink and do not make cold solders. Check that there is no solder paths being made where you don't want them and always check your work before you apply any power.