Hi everyone,
I'm really stuck on this PS Audio and hoping someone can help. I cannot find any schematic information online, so i feel a bit blind. This amp had stopped outputting on the left channel, it just had a loud buzz. If left on long enough, a burning smell would gradually occur. I opened it up and checked the main transistors which are screwed onto the massive heatsink at the back of the unit. One of them - a A1360 was shorted on the left channel. I ordered a replacement online and fitted it. Then, I turned it on while connected to my dim bulb tester. Everything came on fine, and no smoking. I then tested both sides of the unit. When plugging the speaker into the right side - the dim bulb didn't really light up at all and sound worked great. When plugging into the left side, the bulb lit up a bit and a loud hum was heard initially (2 seconds) and then it faded away and the sound worked perfectly. The following day I tested it again and this time (with the speaker cables plugged into the left side) as soon as i turned it on the dim bulb lit up and stayed lit, and I saw an area of the board light up and smoke came out of it. I quickly turned it off. I couldn't see any burned components, but there was a burnt bit of the board around another A1360 in the left channel (top middle of the board). Unfortunately none of the components are marked with component numbers on the board. So - once again I took the board off and replaced this A1360 (it wasn't shorted, but i replaced it anyways to be safe). Turned the unit on again, this time with no speakers connected and did what I should have done after the first A1360 replacement - I checked the speaker outputs for DC offset. turns out the left side has 1.7vdc on the outputs.
Since this discovery, I have checked all transistors on the left side for shorts or partial shorts, as well as the large capacitors for shorts and capacitance readouts. I don't really know what else to do in trying to find the fault when i have no schematic information available. Can anyone help? I recognise it might be impossible. I've attached some photos of the board anyways. The red circled component is the first one which was shorted and replaced, the yellow circled component is the one i saw burn up a bit (but didn't appear to be shorted) it was also replaced.
Thanks!
I'm really stuck on this PS Audio and hoping someone can help. I cannot find any schematic information online, so i feel a bit blind. This amp had stopped outputting on the left channel, it just had a loud buzz. If left on long enough, a burning smell would gradually occur. I opened it up and checked the main transistors which are screwed onto the massive heatsink at the back of the unit. One of them - a A1360 was shorted on the left channel. I ordered a replacement online and fitted it. Then, I turned it on while connected to my dim bulb tester. Everything came on fine, and no smoking. I then tested both sides of the unit. When plugging the speaker into the right side - the dim bulb didn't really light up at all and sound worked great. When plugging into the left side, the bulb lit up a bit and a loud hum was heard initially (2 seconds) and then it faded away and the sound worked perfectly. The following day I tested it again and this time (with the speaker cables plugged into the left side) as soon as i turned it on the dim bulb lit up and stayed lit, and I saw an area of the board light up and smoke came out of it. I quickly turned it off. I couldn't see any burned components, but there was a burnt bit of the board around another A1360 in the left channel (top middle of the board). Unfortunately none of the components are marked with component numbers on the board. So - once again I took the board off and replaced this A1360 (it wasn't shorted, but i replaced it anyways to be safe). Turned the unit on again, this time with no speakers connected and did what I should have done after the first A1360 replacement - I checked the speaker outputs for DC offset. turns out the left side has 1.7vdc on the outputs.
Since this discovery, I have checked all transistors on the left side for shorts or partial shorts, as well as the large capacitors for shorts and capacitance readouts. I don't really know what else to do in trying to find the fault when i have no schematic information available. Can anyone help? I recognise it might be impossible. I've attached some photos of the board anyways. The red circled component is the first one which was shorted and replaced, the yellow circled component is the one i saw burn up a bit (but didn't appear to be shorted) it was also replaced.
Thanks!
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