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I have a Ampeg BA115 bass amp. The unit blows the 2.5 amp fuse as soon as it is turned on. I have isolated the step down transformer from the solid state board and the fuse does't blow. So I know the power transformer is OK. What should I check next, and could you recommend a good repair service.

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SOURCE: My amp turns on then off while it slowly blows the fuse out

If I were a guessing man, I'd guess that you had your amp hooked up in a bridged configuration. And also that you connected your two speakers in parallel (plus to plus and minus to minus). And if I were to further guess, I'd guess that you have a blown amp now because of what I mentioned above. Sounds like you need to spend some quality time with your favorite electronic repair shop. Good luck.

Posted on Feb 23, 2007

SOURCE: amp blows fuses

The fuses are there to protect the internals of the AMP.....
Please check that the correct fuses are installed......
if the incorrect ones are installed then a fire may develope...

There should be a manufacturers lable on the external chassis that details the fuses to use....

Fuses now days can be slow blow or fast the correct fuses must be used.....dont increase the fuse rating past the chassis panel label...but make sure they are correct...if they are correct then the amp needs a service to determine where the peak loadings to the power supply are originating from...

Some one may have installed incorrect fuses in the past...

Cheers from YUBEUT

Posted on Nov 03, 2007

  • 1635 Answers

SOURCE: AMp keeps blowing fuses

When any amp blows fuses, this indicates that something is drawing too much current. The most common cause are components in the output stage and driver stages that have become defective.

On the amp that is blowing the fuse with the volume being turned up, this means that the output stage is partially working. The short or over-draw of current must be in the output stage, or what is loading it. It is possible in this case that a crossover in a speaker unit is defective, and is drawing too much current. I have seen this with especially sub-woofer crossovers, and the driver itself. Subs pull a lot of current because of the amount of drive power required to have very strong bass sounds. Other than that, this still does not rule out the possibility of the problem being defective components in the amplifier.

Jerry G.

Posted on Apr 25, 2008

  • 4234 Answers


There should be an 8 pin IC close to the input jack that will be marked 4558 or 4560. This is an Op-amp Ic that is the most likely cause of the problem. Replace that IC and report the results here.

Posted on May 28, 2008

  • 1512 Answers

SOURCE: Older Peavey PA Head XR600C.

If you need a circuit for the PA board... get it from here

I would start by checking with a multimeter for shorts in driver transistors Q2 and 12

The output stage may be suspect for a driver to have failed. I would disconnect(emmitter and collector) of each output transistor for leakage and shorts in all directions (swap meter leads +ve and -ve). You can often tell at a glance that there IS a short in the output stage, by checking collector emitter with everything still connected. You cannot, however tell if there is leakage that may kill any repair work that you are doing.

Good work on the lamp. I use one in line with the mains socket on my test bench. I use a 40 watt build though.Have seen some smoke with higher wattages. I also use a variac to soft start the unit and do some DC checks mostly for symmetry in output stages with about 40-70 v into the 240 volt mains socket.

Let me know if you find any shorted transpistanators :)


Posted on Jun 13, 2008

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