Backstory:
I bought this amplifier on the forum, "brand new sealed in box". When I got it home and opened the box half the polystyrene packaging material was missing, which I thought unusual for Emotiva to have done... When I turned the amp on there was one faulty channel, it made weird hissing/crackling/popping noises, very loud, entirely unuseable. I almost returned it to the seller, but for a variety of reasons (far drive, matched well with my pre-pro, etc.) I decided to keep it and just use the remaining working channels [it's an 8ch amp, there were some 'spare' channels to choose from!]. As the months went by, another channel developed the same fault, then a 3rd channel and then eventually it would go into protection mode after operating for a few minutes.
The repair:
I contacted Emotiva support, just to see if they had any ideas or it was a common issue, etc. They recommended that I replace the DC offset adjustment trim pots.
I measured the overall resistance of the pots in place, as a quick initial check, and sure enough the values were all over the place, no match between the values measured between the channels. So I figured we were on the right track. I also took this opportunity to measure the DC voltage at each speaker terminal and they were all over the place, some were OK, some were as much as 6.9V.
Emotiva was kind enough to recommend a replacement pot from RS (UK stock though, but shipping took ~1 week).
https://za.rs-online.com/web/p/trimmer-potentiometers/1673349Unfortunately these pots turned out to be the incorrect ones. The pin spacing between the outer pins is 5mm but the spacing between the wiper and the back 2 pins is only 2.5mm. It should be 5mm between both measurements.
The part recommended was bourns 3306P and the correct part would have been 3306F I think.
The first step was to disassemble the whole thing, I needed to get to the bottom of the amplifier board which wasn't accessible when it was in the chassis. It was a fair bit of work to get it all removed!
Next up was removing the old pots and soldering on the new ones. Since I had no intention to re-use the old pots, I just clipped the leads with side cutters and then desoldered the remaining pin out of the hole. I did it this way to avoid damaging the PCB. I used a solder sucker with a piece of silicon tubing (to make a good seal) on the opposite side of the board to the soldering iron to suck the remaining solder out of the holes and cleaned it with a little bit of solder wick/braid where necessary.
Since I had the wrong pin spacing on the pots, I had to bend the pins in order to make them fit into the holes on the PCB. I did this carefully and measured the pots before installation to make sure I hadn't broken them during the bending.
I cleaned bit of flux residue off the board and then reassembled the whole amp. I left the top of the chassis off for now.
The amp powered up and ran for 35min without triggering protection mode, which was a huge step in the right direction compared to before when it would go into protection mode within minutes.
Now that the amp was running the next step was to adjust the newly installed pots. The procedure is to connect a multimeter to each channel in turn and adjust the corresponding pot. I did a quick adjust through each of the channels and then came back for a fine adjustment on a 2nd run. All channels could be adjusted for DC offsets less than 20mV.
Final step was to connect a cheap surround speaker and an input to each channel in turn and confirm that music was playing and sounded correct without any weird distortions, etc.
The verdict
The amp has been reinstalled and is back in active duty! All channels are now working (so it's better than when I first bought it) and producing great sound. Yay!
I bought this amplifier on the forum, "brand new sealed in box". When I got it home and opened the box half the polystyrene packaging material was missing, which I thought unusual for Emotiva to have done... When I turned the amp on there was one faulty channel, it made weird hissing/crackling/popping noises, very loud, entirely unuseable. I almost returned it to the seller, but for a variety of reasons (far drive, matched well with my pre-pro, etc.) I decided to keep it and just use the remaining working channels [it's an 8ch amp, there were some 'spare' channels to choose from!]. As the months went by, another channel developed the same fault, then a 3rd channel and then eventually it would go into protection mode after operating for a few minutes.
The repair:
I contacted Emotiva support, just to see if they had any ideas or it was a common issue, etc. They recommended that I replace the DC offset adjustment trim pots.
I measured the overall resistance of the pots in place, as a quick initial check, and sure enough the values were all over the place, no match between the values measured between the channels. So I figured we were on the right track. I also took this opportunity to measure the DC voltage at each speaker terminal and they were all over the place, some were OK, some were as much as 6.9V.
Emotiva was kind enough to recommend a replacement pot from RS (UK stock though, but shipping took ~1 week).
https://za.rs-online.com/web/p/trimmer-potentiometers/1673349Unfortunately these pots turned out to be the incorrect ones. The pin spacing between the outer pins is 5mm but the spacing between the wiper and the back 2 pins is only 2.5mm. It should be 5mm between both measurements.
The part recommended was bourns 3306P and the correct part would have been 3306F I think.
The first step was to disassemble the whole thing, I needed to get to the bottom of the amplifier board which wasn't accessible when it was in the chassis. It was a fair bit of work to get it all removed!
Next up was removing the old pots and soldering on the new ones. Since I had no intention to re-use the old pots, I just clipped the leads with side cutters and then desoldered the remaining pin out of the hole. I did it this way to avoid damaging the PCB. I used a solder sucker with a piece of silicon tubing (to make a good seal) on the opposite side of the board to the soldering iron to suck the remaining solder out of the holes and cleaned it with a little bit of solder wick/braid where necessary.
Since I had the wrong pin spacing on the pots, I had to bend the pins in order to make them fit into the holes on the PCB. I did this carefully and measured the pots before installation to make sure I hadn't broken them during the bending.
I cleaned bit of flux residue off the board and then reassembled the whole amp. I left the top of the chassis off for now.
The amp powered up and ran for 35min without triggering protection mode, which was a huge step in the right direction compared to before when it would go into protection mode within minutes.
Now that the amp was running the next step was to adjust the newly installed pots. The procedure is to connect a multimeter to each channel in turn and adjust the corresponding pot. I did a quick adjust through each of the channels and then came back for a fine adjustment on a 2nd run. All channels could be adjusted for DC offsets less than 20mV.
Final step was to connect a cheap surround speaker and an input to each channel in turn and confirm that music was playing and sounded correct without any weird distortions, etc.
The verdict
The amp has been reinstalled and is back in active duty! All channels are now working (so it's better than when I first bought it) and producing great sound. Yay!
