Sreekidu, maybe you could solve this problem: My Yamaha YST-MSW10 subwoofer connected with two YST-M20DSP speakers to my Apple PowerMac G5 suddenly quits after about 10 minutes. The speakers keep on working fine. The little red light on the subwoofer weakens and when switching it off and on again or unplug and plug in again the mini jack cord from the right YST-M20DSP speaker it works for another 10 minutes, etc. It's no case of overheating I guess, hight cut/volume high or low makes no difference. It seems if the Auto Power Off function on the subwoofer turns on, but why, the audio signal seems fine. Ido, Holland
This problem can be solved by either of the following:
1/ Modify the PCBA to prevent the auto shut off feature from working. This is done by adding a 20k ohm resistor across pins 1 & 2 on the timer IC6. This resistor will prevent the timer from turning off the amp. To do this, unplug the amp. Remove the 8 screws on the perimeter of the rear of the amp. Carefully remove the rear plate. Disconnect the speaker wires at the speaker and the front panel connection on the main board. Locate IC6 on the bottom of the main board. Solder a 20k ohm resistor (1/4W) across pins 1 & 2. Pin 1 and Pin 8 are noted on the board. Be sure to insulate the leads of the resistor to prevent contact with the board. See picture. Re-assemble in reverse order.
2/ Some 5.1 channel amps allow independent control of the volume for the subwoofer in their setup. Check your amp to see if you can raise the signal level going to the subwoofer to prevent the amp from shutting off. You can then dial back the volume of the subwoofer using the volume control on the front.
rhsweat nailed it! So great. Thank you!
Huh! This was helpfull!
Very helpful indeed! I know I'm probably asking too much ... but it would be ideal if we could lower the threshold to a more reasonable level without completely disabling the auto shut off feature!
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This speaker has a feature that shuts it down automatically when there is no audio signal present for a period of time. Unfortunately, the threshold is set a bit too high so, if you're listening at low volume the speaker will turn off even if there is signal present.
I found this posting because I was looking for a circuit diagram so I could bypass the auto-off feature on my MSW10.
The fault / problem is with the AC to DC power supply in the speaker box.
The problem solution is easier than is documented by answer 1. The IC6 is an integrating comparitor and when the input voltage on pins 2 & 3 reach about 10V or so, IC6 shuts off. It's output is routed to the power amp which shuts off the power amp (and turns off the little power LED in the front). To disable the integration and leave IC6 on all the time, simply clip R64 at the edge of the board. The leakage current passed by the electrolytic integrating capacitor keeps the signal low to IC6 pins 2&3, leaving the power amp on all the time. No extra parts are needed, and simple scissors can be used to break the resistor. If you're PCB solder-friendly, you can unsolder one lead of R64 and lift it out of its mounting hole allowing it to be replaced should you ever want to re-enable the feature.
I did as suggested (clipped R64) but it still shuts off after about 5 minutes.
Probably your capacitor doesn't have enough leakage current, so you can choose to bridge the IC pins as described above. I don't have the unit apart, but I hate soldering directly to IC pins, so if I were you, I'd trace the etch going to those pins and choose a better location I forget, but those pins may go to the capacitor.
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... Sounds great, but what to do about it? The YST-MSW10 subwoofer has its own power supply cord (230V, 25W, 50Hz), the YST-M20DSP speakers are supplied by a PA-M20 AC Power Adapter (in 230V, 50Hz, out 14V). Maybe it's better to connect an amplifier between the Apple PowerMac G5 and the speaker system?
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