Good luck with your repair, but may I ask where you got an Emotiva schematic?
I've been looking without success for drawings to another box they make (Stealth DC-1 DAC).
In general, schematics for this brand are difficult to find. Thanks.
@Kim Christensen : What would be the feedback back that " the 3 opposing output transistors would turn on hard"?
Any info available on the web that would explain the working of the attached schematics especially the negative feedback path?
Hello All,
Need your advice on a Emotiva XPA-3 Gen 1 Audio amp.
My Emotiva XPA-3 Gen 1, blew its 10A fuses last week. The amp consists of 3 identical amp sections (modules) powered in parallel with +65/-65V and further investigation revealed that the power supply inputs to one of the faulty modules had a dead short across the +65V and -65V rails.
I disconnected the power to the faulty module and the rest of the 2 modules were fine which leaves me with a 2 channel amp instead of the original 3 channel amp.
On the failed module, what surprised me was that all the output BJT's, i.e., three PNP NJW0302's and three NPN NJW0281's were a dead short
In addition to this 4 other BJT's as per the attached schematic were also blown (all damaged BJT's marked in red).
Could someone help me understand what chain of events could have led to this catastrophe? Would failure in any one of the marked transistors have led to a chain that caused all output BJT's to fail?
All the ballast emitter resistors have survived, so is there any other part I should check? I checked all other BJT's on the board and all are reading alrite on a diode test using a DMM.
thanks
As i wrote before: With "normal" music you stay well below full amplitude on average and there will only be drum beats or so reaching the limit. But modern pop music is terrible in that respect. They do all sorts of digital processing to fit the largest possible sound level into the digital full scale. And once the amplifier runs hot, it doesn't take much to blow it. It's not clear whether those crashes happen with pro 18" speakers as those usually have light cones for best efficiency. Maybe the OP has more details.
Regards, Dieter
As i wrote before: With "normal" music you stay well below full amplitude on average and there will only be drum beats or so reaching the limit. But modern pop music is terrible in that respect. They do all sorts of digital processing to fit the largest possible sound level into the digital full scale. And once the amplifier runs hot, it doesn't take much to blow it. It's not clear whether those crashes happen with pro 18" speakers as those usually have light cones for best efficiency. Maybe the OP has more details.
Regards, Dieter
It doesn't matter on type of music, it shouldn't cause chain reaction like the OP described.
I'm listening to many kind of music classical, jazz ... and hard core UK punk from 1980 at extreme levels... my amps eventual limited output, but never died
I too am a bit confused to how someone would design a 1000$ amp like this with a chain reaction destroying all the final semicons.
At my regular day job, I have to perform single and double fault analysis......
I too am a bit confused to how someone would design a 1000$ amp like this with a chain reaction destroying all the final semicons.
At my regular day job, I have to perform single and double fault analysis......
As far as I can see this is a pretty common configuration for an audio power amp.
As Capt. Don said earlier, if one output device shorts, then all the devices on the other side pass shitloads of current into this shorted device.
So either these devices also end up short, or the emitter resistors blow instead, saving them.
But it doesn't really save them as nobody would really put these devices back in service after what they've been through.
I too am a bit confused to how someone would design a 1000$ amp like this with a chain reaction destroying all the final semicons.
At my regular day job, I have to perform single and double fault analysis......
As far as I can see this is a pretty common configuration for an audio power amp.
As Capt. Don said earlier, if one output device shorts, then all the devices on the other side pass shitloads of current into this shorted device.
So either these devices also end up short, or the emitter resistors blow instead, saving them.
But it doesn't really save them as nobody would really put these devices back in service after what they've been through.
Sorry, but I did not understand why you would say its not worth repairing after what they have been thru......its a 1000$ amp......any reason why the fault might repeat with new devices in place?