LME49810 from connex burnout..

i got two lme49810 300w into 8ohm module from connex elec and according to the voltage supply specifications everything has been connected. Mounted on a very large heatsink and connecting it to the psu at first I didnt get any output everything was stable but I thought something might be wrong with the protection circuit and connected the output after the RL network at the output and everything started to sing. It worked for 5 mins and suddenly things started to burnout... all the gate resistors of one channel and the driver transistor on the other channel started to burnout the freak part is that the driver was literally split and i can see the casing into two. The lme49810 itself has got a perforation and sooth over the input capacitor.

I really dont know what went wrong but was pretty impressed when compared with 4702. Unfortunately it burnt out. I didnt check the bias current in the beginning but the heatsink was also not getting heated up but I am thinking that the heatsink on the chip itself is too small for the heat dissipation.

any suggestions what might have went wrong? I think the bias might be to high in the beginning which I might have reduced

out of two modules I got one burnt and I want to atleast use the other one properly..

what might have went wrong please suggest me..

the mute voltage was 26v and resistor of 200k was used for the mute functionality is that the problem.??
 

multisync

Member
2008-01-31 10:34 pm
Carp
sounds like the speaker protection was working, it detected an error, did not connect the speakers, you bypassed it and then the amps blew up. You should have looked for a fault, corrected the fault and then tried again. You didn't use the light bulb tester which many diy folks use before powering up any amplifier. You didn't test bench the amplifiers, you didn't set them up etc. From your description both boards failed. They either have the same problem or perhaps there was a problem with the way they were installed.
 

multisync

Member
2008-01-31 10:34 pm
Carp
If you connected the AC sense line to the 230 volt primary, you most likely destroyed every semiconductor on the board. The AC sense line should connect to one of the secondary windings.

Search light bulb tester on this forum.

Look up upc1237, it is probably the chip used in the protect circuit of your board.
 

llwhtt

Member
2008-06-12 3:43 am
SoCal
You have posted many many times here and there about these multi-hundred watt amplifiers yet it seems you have no electronics experience at all. Why don't you start with something small and easy until you have some experience, say at least a few years. It's like you just got your drivers license and you trying to win a Formula 1 race on your first try.

Craig

P.S. You need to invest in some test equipment if you want to continue.
 
The AC sense line should connect to one of the secondary windings.

.

The AC sense line is to dectect if the power is switched on, then delay a few seconds and connect the speaker if all is well. The other function of the AC sense line is to imediatly disconnect the speakers when the power is turned off. If the power for the outputs transistors is soft started, how long is the soft start delay? Hopefully the soft start delay is shorter than the relay delay for the protection circuit.

Connect the AC sense to the secondary of the the transformer before the rectifier diodes. Were you given any recommended connections and set up for your board.
 
You have posted many many times here and there about these multi-hundred watt amplifiers yet it seems you have no electronics experience at all. Why don't you start with something small and easy until you have some experience, say at least a few years. It's like you just got your drivers license and you trying to win a Formula 1 race on your first try.

Craig

P.S. You need to invest in some test equipment if you want to continue.

the module is not my own design. I have built small amplifiers upto 100W

just got this module and this does not have enough documentation on AC sense for which i plugged it to the mains..
 
yep, page 8 of the document linked on the product page describes a rather detailed setup schematic, not bad at all for a diy module. AC sense, thermal and all the other protection measures and connections are discussed and illustrated

@rhythmsandy: I agree with others, you really need to learn how to read schematic properly and take some baby steps before taking on projects and concepts you clearly dont understand
 
The AC sense line is to dectect if the power is switched on, then delay a few seconds and connect the speaker if all is well. The other function of the AC sense line is to imediatly disconnect the speakers when the power is turned off. If the power for the outputs transistors is soft started, how long is the soft start delay? Hopefully the soft start delay is shorter than the relay delay for the protection circuit.

Connect the AC sense to the secondary of the the transformer before the rectifier diodes. Were you given any recommended connections and set up for your board.

the delay of the softstart is less than a second
 
the module is not my own design. I have built small amplifiers upto 100W

just got this module and this does not have enough documentation on AC sense for which i plugged it to the mains..

the document clearly illustrates connecting AC sense via a Zener diode to the SMPS +Vdrv output (higher voltage driver supply for the LME49810), or the secondary side of a linear transformer powered supply. the documentation is actually quite good, particularly for such a cheap product.

So I think its unfair to place any blame whatsoever on connex, i'm afraid this is all on you for not reading the document and not exercising proper care. I was able to find the instruction within 1 minute....

That and honestly, thinking that bypassing the protection circuitry and connecting the full unadulterated mains voltage to a sensing/logic circuit and connecting it up to your speakers to test was a good idea, says to me that you should not be building stuff of this power yet. you are lucky your speakers survived, if indeed they did survive. AC just means alternating current, ie. not DC, it doesnt necessarily mean mains voltage AC. if mains voltage was meant, it would be accompanied by a warning.

being able to buy finished high power amp modules ready to go, with the only thing needed being to connect it all up is a double edged sword. It has an advantage that people without much DIY experience, can put together something significant, without having to understand how the circuit works. It has a disadvantage that people without much DIY experience, can put together something significant, without having to understand how the circuit works....
 
now for the second module I have connected the AC sense to the secondary of the output stage transformer and everything started to work fine.. first the softstart of the outputstage triggered in 1 second and after 3 seconds the protection relay started. It was good everything was fine for 5 mins and after that the decoupling capacitors have burned out... this time i dont see any resistor or IC or anything burning and as soon as I saw smoke coming out of the capacitors i turned it off. Actually it had cheap sanyo 39uf / 100v caps. The actual image at the purchasing time was Nichicon blue capacitors. I think need to recap all the decoupling caps and let me see if the board survived. This time everything was done properly but found the caps failure..
 
replaced all the capacitors now the capacitors on 2sa1943 side are heating up and quite warm...

the protection ckt is working and the relay didnt turn on at the output... seems something is wrong here

I believe the output transistors of 1943 side damaged? what could be the reason the capacitors are warmingup...