I just went to wire up a 12v 2.1ah battery to a brand new MAH3 amp from Guitar Fuel and after a few seconds...smoke and a dead amp. I thought I got confused and mixed up the polarity so I VERY carefully wired up the battery to my second MAH3.... SHIT...two dead amps.
They say it can take between 9 and 15 volts and I hooked the battery up to the 9v battery clip wires. I may be mistaken but Id swear the power switch wasn't even on.
I tried contacting guitar fuel but have heard nothing back.
Anyone have any ideas on what I should do to check things out to see if there is any salvaging that can be done?
I feel absolutely sick about this...please help!
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Good topic Tom, sorry to hear about the amps. Thanks for sharing as it helps the guys like me that are still on the learning curve so to speak, it's threads like these that a guy like me can learn a thing or 2. Hopefully the amps can be salvaged, good luck and hope it all turns out right for ya. I'll keep an eye on the thread to see the remody.
Well, one amp still lives via the external power supply jack. I wired in my 12v battery into the wiring for the jack socket and all is well. The 9 volt battery input is dead. I'm thinking a capacitor may well have blown but to be honest I'm not gonna mess with it anymore, it works and I'm happy. That 12 volt battery should run the amp for hours and it's rechargable so I will pop that into the amp box and and have a connector for it's charger...done.
The other amp is still dead no matter what power input I use and schematics aren't available so it goes into the file marked "spares from lessons learned".
All of this aside the amp itself sounds great with an 153X 100MM 4W 8 OHM general purpose elliptical speaker. I'm getting a 4 watt, 8 OHM round, 125mm GP speaker soon and will try that to see what the difference is.
Interesting, sorry to hear about the fried amps. I was think about running 12V into my Ruby amp with a 386 chip but wonder now if I should not, or if I need to connect it to a different point on the board?
Jim Woods > BluesheartSeptember 18, 2012 at 2:20pm
I have been using the LM386 N1 chips (nominally 4v - 12v ) in my amps - I have used them w/ a "12v" car cord on the boat while the shore powered charger was on - usually about 13v with no problem. I do use the socket for the chip, so if I fry one (haven't yet thru the 1st 6 amps) it is a 75 cent no solder swap out.
Bluesheart, it is possible to run LM386 amps at up to 18v
You need to make sure all the components are rated for at least the supply voltage you plan to use.
LM386 chips come in several versions with different maximum supply voltage ratings. The N1 and N3 versions are rated for up to 12v, while the N4 version is rated for up to 18v.
They also have different maximum power output ratings.
For other components, such as capacitors and resistors, I generally find I end up with stuff rated at higher voltages - 25v or more - so there's rarely a problem on that front. But it's always worth double checking.
mah is still irrelevant to this though - the point of quoting mah figures is mostly to allow you to estimate how long a battery will take to discharge in a given application
One further thought - are you sure you got the polarity right when you connected the battery? If you connected it the worng way around then it's quite possible you cooked the electrolytic capacitors as they don't like reverse voltages.
If it's the capacitors that have been knackered then in theory you could probably remove them and solder new ones in their place, however that would require good soldering skills.
If it says 9 to 15v then a 12v source ought to be fine. All the stuff about battery capacities (ie. the figs quoted in mAh) is largely irrelevant to the problem in question. The circuit will draw a current dependent on the voltage applied across it - and it seems the voltage you applied was well within the specification.
On the face of it they have a case to answer and you shouldn't beat yourself up over it (although perhaps you should check the instructions for any small print that says not to connect 12v batteries where you did - it's distantly possible there's a built-in voltage regulator that works on the mains adaptor input but not on the battery input).
Also, if you can lay your hands on a voltmeter it's worth checking what the actual voltage is on the battery terminals. (That's because ratings such as 1.5v, 9v and 12v are only nominal. The true voltage tends to be slightly different - although I'd be surprised if it was sufficiently different to take you over 15v)
To figure out more I'd need to know the details of the components used in the circuit. Also, whereabouts exactly did the smoke come from? (ie. can you tell me whether it came from a particular component on the circuit board?)
Obviously it looks like they used at least one component that had a maximum design voltage below 12v. I'm guessing maybe a capacitor, but it could be something else.
Check to see if you can see any voltage figures printed on any of the components (especially the electrolytic capacitors, which are the cylindrical things between the pot and the intergrated circuit chip)
Also, can you see any writing or numbers printed on the chip? If we can identify the chip then it should be possible to find and download a datasheet that will say what voltage range it was designed for.
Replies
Good topic Tom, sorry to hear about the amps. Thanks for sharing as it helps the guys like me that are still on the learning curve so to speak, it's threads like these that a guy like me can learn a thing or 2. Hopefully the amps can be salvaged, good luck and hope it all turns out right for ya. I'll keep an eye on the thread to see the remody.
Well, one amp still lives via the external power supply jack. I wired in my 12v battery into the wiring for the jack socket and all is well. The 9 volt battery input is dead. I'm thinking a capacitor may well have blown but to be honest I'm not gonna mess with it anymore, it works and I'm happy. That 12 volt battery should run the amp for hours and it's rechargable so I will pop that into the amp box and and have a connector for it's charger...done.
The other amp is still dead no matter what power input I use and schematics aren't available so it goes into the file marked "spares from lessons learned".
All of this aside the amp itself sounds great with an 153X 100MM 4W 8 OHM general purpose elliptical speaker. I'm getting a 4 watt, 8 OHM round, 125mm GP speaker soon and will try that to see what the difference is.
Thanks all.
Interesting, sorry to hear about the fried amps. I was think about running 12V into my Ruby amp with a 386 chip but wonder now if I should not, or if I need to connect it to a different point on the board?
I have been using the LM386 N1 chips (nominally 4v - 12v ) in my amps - I have used them w/ a "12v" car cord on the boat while the shore powered charger was on - usually about 13v with no problem. I do use the socket for the chip, so if I fry one (haven't yet thru the 1st 6 amps) it is a 75 cent no solder swap out.
You need to make sure all the components are rated for at least the supply voltage you plan to use.
LM386 chips come in several versions with different maximum supply voltage ratings. The N1 and N3 versions are rated for up to 12v, while the N4 version is rated for up to 18v.
They also have different maximum power output ratings.
For other components, such as capacitors and resistors, I generally find I end up with stuff rated at higher voltages - 25v or more - so there's rarely a problem on that front. But it's always worth double checking.
mah is still irrelevant to this though - the point of quoting mah figures is mostly to allow you to estimate how long a battery will take to discharge in a given application
That was my understanding as well...like I mentioned, I think amperage is only "supplied" as the device demands it...ish.
One further thought - are you sure you got the polarity right when you connected the battery? If you connected it the worng way around then it's quite possible you cooked the electrolytic capacitors as they don't like reverse voltages.
If it's the capacitors that have been knackered then in theory you could probably remove them and solder new ones in their place, however that would require good soldering skills.
You think amps and volts I don't know the specs for that amp but I thinks Wes is right.
I use 7.4 Lithium on 386 and they are 5oomah this it what most these chip can handle.
More volts adds some volume and more heat, these batts run the chip at 85-90 degrees.
if I want my amps to rattle your teeth i put a pedal in front of it.
If it says 9 to 15v then a 12v source ought to be fine. All the stuff about battery capacities (ie. the figs quoted in mAh) is largely irrelevant to the problem in question. The circuit will draw a current dependent on the voltage applied across it - and it seems the voltage you applied was well within the specification.
On the face of it they have a case to answer and you shouldn't beat yourself up over it (although perhaps you should check the instructions for any small print that says not to connect 12v batteries where you did - it's distantly possible there's a built-in voltage regulator that works on the mains adaptor input but not on the battery input).
Also, if you can lay your hands on a voltmeter it's worth checking what the actual voltage is on the battery terminals. (That's because ratings such as 1.5v, 9v and 12v are only nominal. The true voltage tends to be slightly different - although I'd be surprised if it was sufficiently different to take you over 15v)
To figure out more I'd need to know the details of the components used in the circuit. Also, whereabouts exactly did the smoke come from? (ie. can you tell me whether it came from a particular component on the circuit board?)
Obviously it looks like they used at least one component that had a maximum design voltage below 12v. I'm guessing maybe a capacitor, but it could be something else.
Check to see if you can see any voltage figures printed on any of the components (especially the electrolytic capacitors, which are the cylindrical things between the pot and the intergrated circuit chip)
Also, can you see any writing or numbers printed on the chip? If we can identify the chip then it should be possible to find and download a datasheet that will say what voltage range it was designed for.
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