hi, I built my first Gainclone lm3886, and have experience in electronics but....
can anybody explain why I get -42 volt on both output on speaker, blew my first with smoke so now i build it again and same result but no speaker connected.
I have supplied it with 42 and -42 as powersource dual rail.
i dubble sjekked connection and solder point and cant understand why.
Anybody that knows where the problem could be ?
Niklas.
this is the reference i build after.
DIY HiFi Gainclone Power Amplifier (2x68w, Class AB-A, LM3886) : Getting To Know Your LM3886 (I.C./Chip)
can anybody explain why I get -42 volt on both output on speaker, blew my first with smoke so now i build it again and same result but no speaker connected.
I have supplied it with 42 and -42 as powersource dual rail.
i dubble sjekked connection and solder point and cant understand why.
Anybody that knows where the problem could be ?
Niklas.
this is the reference i build after.
DIY HiFi Gainclone Power Amplifier (2x68w, Class AB-A, LM3886) : Getting To Know Your LM3886 (I.C./Chip)
Hi
You are running your LM3886 at very close or possibly exceeding absolute maximum voltage😱, try it instead at 28+ and 28- and use an appropriate heatsink.🙂
I see, but you think thats why its put out -42 volt on both channels......
But I will try with lower voltage.
but limit is 84 volts max according to data sheets.
But I will try with lower voltage.
but limit is 84 volts max according to data sheets.
When reading a datasheet like the one for the LM3886 you need to work through some of the typical design examples. For instance page 21 gives design of a 40w into 4Ohm amplifier and specifies
21 v+/- at 4.5 amps as suggested supply. It is likely your 42+ and 42- supply was unregulated and drifted or peaked momentarily past the LM3886's maximum ratings, or the device power dissipation was exceeded by insufficient heatsink.
Your LM3886 may have survived, but test for voltages first once you connect 28+/- to see if it has
returned to normal. If not then replacement may be needed.
21 v+/- at 4.5 amps as suggested supply. It is likely your 42+ and 42- supply was unregulated and drifted or peaked momentarily past the LM3886's maximum ratings, or the device power dissipation was exceeded by insufficient heatsink.
Your LM3886 may have survived, but test for voltages first once you connect 28+/- to see if it has
returned to normal. If not then replacement may be needed.
You can do some simple tests to find the cause rather than groping around in the dark 😉
Can you post a schematic of your implementation?
Is the +supply present at the right pin?
What's the voltage at the input pins?
You may have a circuit issue with the 3886 working fine.
Jan
Can you post a schematic of your implementation?
Is the +supply present at the right pin?
What's the voltage at the input pins?
You may have a circuit issue with the 3886 working fine.
Jan
Thanks I see,
but in last try I reassamble new components and connected only power supply, no audio or speaker connected. so only the 42 volts, maybe the ic is a bad batch?
still i will try to find a new lower supply and try.
🙂
but in last try I reassamble new components and connected only power supply, no audio or speaker connected. so only the 42 volts, maybe the ic is a bad batch?
still i will try to find a new lower supply and try.
🙂
im not at home because of work til tomorrow, but, i tok the module with me and maybe there is a little rift in the ground line from pin 7 on the right chip, seems to be maybe lite copper left, did not see this yeasterday. could a bad grounding cause this symtom...?
.
This sounds like a case of looking right at it and not seeing it. Don't feel bad, we all do it. I myself have attained the level of Master of How Could I Be Be So Stupid.
The only semi-successful cure I know of is to start at pin 1 and work outward. Check back and forth between the real-world board and the schematic. Compare what is connected to what should be connected.
Then go to pin 2, same thing. And so on for each pin.
Then to the various inputs/outputs/potentiometers/whatever. Proceed in an organized manner, going clockwise. Always first checking what is there, then looking at the schematic to see what should be there.
But even before that look at the power supply leads. You'll find they're connected backward, and one is connected to the input pin. Or if not that specifically, then it's something like that. It's always something like that.
All of this sounds like it will take forever, but it really doesn't. And you end up much more familiar with the circuit.
I say this method is semi-successful. The other part of the semi is stomping on the accursed thing and starting over. This doesn't always work either, but it makes you feel better.
.
This sounds like a case of looking right at it and not seeing it. Don't feel bad, we all do it. I myself have attained the level of Master of How Could I Be Be So Stupid.
The only semi-successful cure I know of is to start at pin 1 and work outward. Check back and forth between the real-world board and the schematic. Compare what is connected to what should be connected.
Then go to pin 2, same thing. And so on for each pin.
Then to the various inputs/outputs/potentiometers/whatever. Proceed in an organized manner, going clockwise. Always first checking what is there, then looking at the schematic to see what should be there.
But even before that look at the power supply leads. You'll find they're connected backward, and one is connected to the input pin. Or if not that specifically, then it's something like that. It's always something like that.
All of this sounds like it will take forever, but it really doesn't. And you end up much more familiar with the circuit.
I say this method is semi-successful. The other part of the semi is stomping on the accursed thing and starting over. This doesn't always work either, but it makes you feel better.
.
Don't know the number - don't have a datasheet in my pocket 😉.
Is pin 11 de V+ pin?
Is it connected to V+?
Is there +42 V on that pin?
This really is by far the most common error.
You have -42V on the output?
First thing to check is whether V+ is connected.
This is basic, just some common sense thinking.
Jan
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An externally hosted image should be here but it was not working when we last tested it.
pinouts
got 1 and 5 with +42 and 4 and 8 at -42.
but at pin 8 after the resistor i got low reading, i will sjekk the voltage tomorrow.
and check the signalground line from pin 7
And pin 5. Not sure you need both, probably better for low loss.
You have a multimeter?
You can post a schematic?
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An externally hosted image should be here but it was not working when we last tested it.
here it is.
I have multimeter,
One thing to remember is that an opamp always tries to keep its inputs equal.
So one test is to short the input, then measure the DC at the + and - input, that will tell you if the amp still works OK.
Jan
So one test is to short the input, then measure the DC at the + and - input, that will tell you if the amp still works OK.
Jan
ok, sorry, but can you explain that little more in detail please... 🙂
which input =? and which pins cause i have 2 ic on board.
should i short pin 1 to ground on one side ?
good to know if the amp works. 🙂
which input =? and which pins cause i have 2 ic on board.
should i short pin 1 to ground on one side ?
good to know if the amp works. 🙂
Well there must be an input to the amp, no? That's what you short to ground. On the chip that gives the -42.
Or do both chips give the -42 output?
Then you measure the DC voltage on the + and - input pins on the chip.
BTW You may want to verify that the output still rials up to -42 with the input shorted.
Jan
You may have "nicked" the insulation on the TF version.
The LM3886TF version has a higher thermal impedance than the LM3886T -- the statement to use the lower rail voltages for the TF is well advised.
The LM3886TF version has a higher thermal impedance than the LM3886T -- the statement to use the lower rail voltages for the TF is well advised.
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