Help fixing a burnt out amp

[Prime]

While trying to amplify a speaker i burnt out my amp, presumably because I used a 12 volt source instead of a 9 volt source. (I was in too much of a hurry)

On closer inspection, the only thing that seems visibly damaged is a rather cremated resistor on the incoming power connection which is puzzling because that would seem to suggest too much current.

Problem is, I can't read the rating on the resistor any longer. Its wire wound with a ceramic covering which was brown and is now rather blackened.

I've tried testing the resistor but i get 0.3 ohms. which means the resistor is clearly finished. Any idea what value it should be? I was thinking at least a few Kohms.

Any ideas? Amp is one channel and doesn't appear to have a brand. It was given to me by someone years ago. Its definately old. underside of the board says "Japan"

Would a Picture help?

[Hex_Rated]

A few kOhms. What was the amp used for? Definitely not a car amp because that would be 12V source. 9V single channel amps aren't very common in consumer electronics. Maybe a PC speaker with an AC adapter.

You'd need a circuit diagram or schematic to fix it quick. What is the RMS or PMPO output? I'm guessing not very much. Any resistors near to it that look similar? Usually when I blow up hardware it's the diode or regulator (3 pin IC) that pops, are you sure it's a resistor and not a diode? Diodes can sometimes look a bit like resistors.

[RobThePyro]

Pic would help please. both sides of the board

If ur in a hurry, you could prob get a similar replacement from www.zen.pqsound.co.za look under audio modules D.I.Y.

Rob~

[Prime]

A few kOhms. What was the amp used for? Definitely not a car amp because that would be 12V source. 9V single channel amps aren't very common in consumer electronics. Maybe a PC speaker with an AC adapter.

You'd need a circuit diagram or schematic to fix it quick. What is the RMS or PMPO output? I'm guessing not very much. Any resistors near to it that look similar? Usually when I blow up hardware it's the diode or regulator (3 pin IC) that pops, are you sure it's a resistor and not a diode? Diodes can sometimes look a bit like resistors.

I don't know what the amp was originally intended for. The guy who previously own it, fixed radios and those sorts of things.
it probably drove a mic and speaker. The Guy died about 3 years ago, so i can't ask him.


Oh and the original amp had 2 3.5mm mono connectors. one in and one out. i fitted it into a box with RCA plugs.

I wanted to use it on a centre Speaker for the PC.



Burnt out component. Looks like a wire wound resistor.



top view of circuit board



Underside. i think i'll need to take a better picture

[RobThePyro]

bigger pics would be nice so we can see whats going on lol

DUDE, imo that board looks OLD tech... If i was you id just get a new mono amp, what is the rating of the speaker? im assuming its not high and something like This 15W mono amp would work, but they also do a 30W, a 50W and higher(up to 140W mono i think) That 15w is like R60 thou imo much easier than fixing that other one lol.. but if u really want to you could lol...

[Prime]

bigger pics would be nice so we can see whats going on lol

DUDE, imo that board looks OLD tech... If i was you id just get a new mono amp, what is the rating of the speaker? im assuming its not high and something like This 15W mono amp would work, but they also do a 30W, a 50W and higher(up to 140W mono i think) That 15w is like R60 thou imo much easier than fixing that other one lol.. but if u really want to you could lol...

Ya, i think you are right. um, its a 3W 8ohm speaker. It came out of a Nokia Car kit.

It might be worth just getting a new speaker while i'm at it

[RobThePyro]

LAWL DUDE!!! ahahahha from nokia kit rofl...

um, I think you could hit one of These and one of These Should be pretty decent imo, MUCH better than silly three watt out of a nokia thing lol...

Rob~

[Prime]

LAWL DUDE!!! ahahahha from nokia kit rofl...

um, I think you could hit one of These and one of These Should be pretty decent imo, MUCH better than silly three watt out of a nokia thing lol...

Rob~

Ya, i was being resourceful.

Na, i'll hopefully invest in a decent surround sound kit at the end of the year

[Samaya]

That resistor won't be in the high ohmage range. It sits in the supply line and is only there to protect the rest of the circuit against over voltage, which you caused... I would suggest taking an adjustable power supply set it to 4V and then start turning up the voltage. Check what the current is while you are doing that. That way you will see if anything else has blown. I can almost bet you that your power transistor is missing a couple of electrons. Unless your amp is not rated for 8ohm but for 32Ohm which will also cause this and not the 12V that you put on it.

[Prime]

That resistor won't be in the high ohmage range. It sits in the supply line and is only there to protect the rest of the circuit against over voltage, which you caused... I would suggest taking an adjustable power supply set it to 4V and then start turning up the voltage. Check what the current is while you are doing that. That way you will see if anything else has blown. I can almost bet you that your power transistor is missing a couple of electrons. Unless your amp is not rated for 8ohm but for 32Ohm which will also cause this and not the 12V that you put on it.

I Have pretty much decided that the amp is a goner. A whole bunch of the connections on the bottom have also gone now, proving its showing its age.

Ag, it was free, when i have some money i'll buy a new one( and not blow it)

But thanks anyway. i may try it for interests sake