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Old 22nd July 2011, 10:31 AM   #1
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Default Did my LM3886 chips just die on me??

Ok, just recieved my two mono amp board from ebay, its a LM3886*3 mono amp.

150W LM3886 X 3 mono channel Audio Amplifier Board HiFi | eBay

I wanted to have a little play with it, but all i had was a 21VDC power pack, so hooked it up to the power, a diskman, and a lose speaker i had. it ran softly for a little bit then faded out. now i can't get anything out of it at all. Is it possible i blew the chips, the chips didn't get hot.
The power pack was 21V/250mA output, is it possible it drew too much current, and killed it cause it's under volted

rick

Last edited by richard.C.; 22nd July 2011 at 10:35 AM. Reason: poor gramma
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Old 22nd July 2011, 10:37 AM   #2
AndrewT is offline AndrewT  Scotland
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Most chipamp amplifiers require a 3wire power supply.
+ve, ZeroVolts & -ve.

You may have killed the amp by only supplying one half of the required supply.
It would not fall over and die because you supplied too little current.
The PSU may have given up.
Can you check voltages?
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Old 22nd July 2011, 10:48 AM   #3
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yes, i just thought about the ground supply then, sheezz. the power supply still works, its just a little phone power pack, supplying 21VDC+/- no ground. you think this is the problem, is the chips gone you think?
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Old 22nd July 2011, 10:51 AM   #4
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i didn't run the amp from the rectifier/power supply, just the power pack itself. i might try again, running the ground wire from the power supply. let ya's know shortly if it works
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Old 22nd July 2011, 10:52 AM   #5
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My stereo LM3886 amp draws 10W at idle (as measured using a 240V power consumption meter), your 21V powersupply as well as being a single supply only as Andrew mentions, will only be capable of supplying around 5W. I'd say it is highly probable you have blown the power supply. It may also be possible the powersupply has a thermal fuse or perhaps a polyswitch in it to protect against overload, if a polyswitch it should start working again once the load has been removed for a while.

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Old 22nd July 2011, 10:54 AM   #6
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Caution! I've never seen a + 0V - plugpack supply, are you sure it is a +- 21v supply? Measure with the multimeter first to make sure

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Old 22nd July 2011, 10:57 AM   #7
Mooly is offline Mooly  United Kingdom
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You can't run an amp designed for split supplies froma single without major modification.

Are the chips dead... it's 50/50 although if they didn't get hot then probably OK. They heat up so quick under fault conditions and cool down quick it can be hard to be sure.

It probably played and "faded out" because there must have been DC across the speaker that drew excess current causing something to shut down... either safely or not !

Power it up with the proper supply and a bulb tester.
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Old 22nd July 2011, 11:02 AM   #8
AndrewT is offline AndrewT  Scotland
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21Vdc, with +- on the connector is a single polarity supply.

The amplifier needs a dual polarity supply.
This would be +21Vdc, 0Vdc, -21Vdc with a total of 42Vdc between the +ve and -ve. The dual polarity requires a 3wire connection, not a 2wire connection.
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Old 22nd July 2011, 11:11 AM   #9
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well i'm assuming they're dead. i haven't got + 0 - supply to confirm this, and so it doesn't sound hopeful at this stage. curiosity killed the chip amp.
Anyone else had this experience before, having the same concerns and issue i have had now?

Last edited by richard.C.; 22nd July 2011 at 11:15 AM.
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Old 22nd July 2011, 11:22 AM   #10
Mooly is offline Mooly  United Kingdom
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Richard... were the chips on a heatsink when you powered this up ?

Even if they are dead, and they may not be, it's minutes work to replace just the chips.

Is your other PSU in the other thread up and running ? even if the DC is somewhat high.
There are always ways and means... well usually anyway. If so run the amp up with a really low wattage bulb in series with the mains and do some voltage measurements.
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