The sub developed a constant popping every couple seconds from woofer and power LED flickering with nothing but wall AC connected. Connecting an audio cable didn't change anything. It doesn't play but a second or two of audio in between the pops.
Opened it up and discovered the power supply is making a faint clicking or ticking sound.
I measured the amp's output to the woofer and it pulses up to 50mv DC to be driver. The pulses coincide with the power supply ticking/clicking.
I measured the power supply output going to the amp board and it too has this pulsing. Voltage cycles between 9v and 40v DC
It's like the power supply is trying but failing to power up fully. I've read this is common behavior in switch mode power supplies that are detecting over voltage or under voltage.
I measured all caps on all boards (3 boards...power supply, amp, and input) and they all measure ok. I removed all but the two biggest caps from the PS board and they all measured ok (ESR and capacitance). I couldn't desolder the two biggest caps because my iron doesn't get hot enough for the huge leads, but measuring them in place showed they were ok. Btw, I measured all the caps in circuit and then removed them and re-measured and the results were the same.
I measured all transistor type devices on all the boards and they all seemed to measure ok based on my limited knowledge.
Only two transistor type devices measured "shorted" on the outer pins in circuit, but I removed them and they measured ok out of circuit. They are a pair of BYV32E 200 PJA1921 C4 9115 that are at the output of the PS board. I took them out of circuit and the short went away. I don't know if another component coupled to them is shorted, but I couldn't find it. I reinstalled them.
Disconnected the amp board from the two smaller boards (amp board and input board) didn't change the noise the power supply is making so I assume this means the fault is in the power supply. BUT I think the IC for the power supply may be on the amp board, which could complicate matters. I don't see an IC anywhere on the amp board and there is a connector between the PS board and amp board with both the a three line power connection (+, - and ground), but a fourth line called OPTO, which may be the link to the PS's pair of optocouplers that control power regulation and feedback.
I don't want to spend too much repairing this. I might spend $20 on a new pair of those suspect BYV32E 200's, a second pair of transistors on the PS board and some various capacitors, and basically giving up if that doesn't fix it.
Thoughts? What else should I check?
THANKS!
Opened it up and discovered the power supply is making a faint clicking or ticking sound.
I measured the amp's output to the woofer and it pulses up to 50mv DC to be driver. The pulses coincide with the power supply ticking/clicking.
I measured the power supply output going to the amp board and it too has this pulsing. Voltage cycles between 9v and 40v DC
It's like the power supply is trying but failing to power up fully. I've read this is common behavior in switch mode power supplies that are detecting over voltage or under voltage.
I measured all caps on all boards (3 boards...power supply, amp, and input) and they all measure ok. I removed all but the two biggest caps from the PS board and they all measured ok (ESR and capacitance). I couldn't desolder the two biggest caps because my iron doesn't get hot enough for the huge leads, but measuring them in place showed they were ok. Btw, I measured all the caps in circuit and then removed them and re-measured and the results were the same.
I measured all transistor type devices on all the boards and they all seemed to measure ok based on my limited knowledge.
Only two transistor type devices measured "shorted" on the outer pins in circuit, but I removed them and they measured ok out of circuit. They are a pair of BYV32E 200 PJA1921 C4 9115 that are at the output of the PS board. I took them out of circuit and the short went away. I don't know if another component coupled to them is shorted, but I couldn't find it. I reinstalled them.
Disconnected the amp board from the two smaller boards (amp board and input board) didn't change the noise the power supply is making so I assume this means the fault is in the power supply. BUT I think the IC for the power supply may be on the amp board, which could complicate matters. I don't see an IC anywhere on the amp board and there is a connector between the PS board and amp board with both the a three line power connection (+, - and ground), but a fourth line called OPTO, which may be the link to the PS's pair of optocouplers that control power regulation and feedback.
I don't want to spend too much repairing this. I might spend $20 on a new pair of those suspect BYV32E 200's, a second pair of transistors on the PS board and some various capacitors, and basically giving up if that doesn't fix it.
Thoughts? What else should I check?
THANKS!
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