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
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
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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.
Tony.
Tony.
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.
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.
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.
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.
no they were not on a heat sink when i powered it, it was gonna be a short test to see if they worked. They did, then didn't. And i turfed that transformer i mentioned in the other thread, the voltage was too high (i believed) 35V+ 0 35-, so it went in the trash.
I'm gonna get a 25-0-25 toroidal transformer then go from there. If the chips are gone, i'll just source some and replace them. On that note, would you anyone know of any suppliers of the LM3886 chip in small quantaties.
I'm gonna get a 25-0-25 toroidal transformer then go from there. If the chips are gone, i'll just source some and replace them. On that note, would you anyone know of any suppliers of the LM3886 chip in small quantaties.
Not sure what component distributers you have in your locale... Farnell ? but you'll get hit with minimum order quantities unlsess you make the order up... tranny from there maybe ?
Just very quickly scanning the data sheet and it reads as though there are isolated and non isolated versions of the 3886 with the tab connected to the -ve pin... something to check and be aware of as it would mean the heatsink would have to be isolated. Or use thermal pads to provide insulation. You could measure that on yours to check.
Get the PSU working first and take it one step at a time.
Just very quickly scanning the data sheet and it reads as though there are isolated and non isolated versions of the 3886 with the tab connected to the -ve pin... something to check and be aware of as it would mean the heatsink would have to be isolated. Or use thermal pads to provide insulation. You could measure that on yours to check.
Get the PSU working first and take it one step at a time.
Farnell seem to have them at different prices but one price is $8.95 each (which is going to be almost as much as what you paid for the entire kit). free shipping though and the minimum order is $10.00.
I bought mine around 5 years ago from futurlec Futurlec, The Electronic Components and Semiconductor Superstore They ship out of singapore, and it takes a couple of weeks, but the price is much better at $4.20 each (not sure if these prices are ex or with gst).
I was concerned at the time when I bought mine that they might be fakes but they weren't, can't vouch for that now though.
Also if the rubbish hasn't been collected get that transformer back out, there will come a time when you will want it for another project
Tony.
I bought mine around 5 years ago from futurlec Futurlec, The Electronic Components and Semiconductor Superstore They ship out of singapore, and it takes a couple of weeks, but the price is much better at $4.20 each (not sure if these prices are ex or with gst).
I was concerned at the time when I bought mine that they might be fakes but they weren't, can't vouch for that now though.
Also if the rubbish hasn't been collected get that transformer back out, there will come a time when you will want it for another project
Tony.
If you connected the supply to pins V- and V+, the filter caps probably made a "pseudo" ground for a second until the voltage got thrown off and the music faded. I doubt you did any harm with that weak supply.
The chips should operate below the minimum rated supply voltage, so here is what you can do to test the board. Take two 9v batteries and battery clips and connect to the power connections. The black wire of one battery goes to V-, the red to ground (center screw) the black of the second battery goes to ground and red to V+. Only after the batteries are connected, connect a speaker to the output and your music player to the input. Slowly bring up the volume. Do not play loudly without a heatsink.
The 3 chips will drain the batteries quickly, so this is only recommended for a few minutes of testing.
The chips should operate below the minimum rated supply voltage, so here is what you can do to test the board. Take two 9v batteries and battery clips and connect to the power connections. The black wire of one battery goes to V-, the red to ground (center screw) the black of the second battery goes to ground and red to V+. Only after the batteries are connected, connect a speaker to the output and your music player to the input. Slowly bring up the volume. Do not play loudly without a heatsink.
The 3 chips will drain the batteries quickly, so this is only recommended for a few minutes of testing.
Yes!! thank you Johnr66 for your suggestion, i tried it and there is still life in these chips. I alternativly swapped + to gnd, - to -/ + to +, - to gnd. I got music signal to my speakers. So thats looking up now.
Well i went and bought some six LM3886TF chips on ebay for $16 to replace these, but now they will be spare for when or if i need them.
But thanks again all, my project is back on track.
Well i went and bought some six LM3886TF chips on ebay for $16 to replace these, but now they will be spare for when or if i need them.
But thanks again all, my project is back on track.
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