Re: entropy continued?
Posted: Mon Apr 22, 2019 6:00 pm
Well Finally got some time to test out my infinity subwoofer that had been malingering for 2 decades. And it doesn't. There is sound, but at very low level. Bit of basic fault finding and oddly the output does not change if the output relay is activated or not. If the relay is open there is a 10k resistor in series with the woofer coil. OK that would do it. It would be way too much good luck for the obvious electromechanical component to have gummed up in the open position.
But the bad luck is that, even if it was, this was not a unit designed for servicing. No plate amp on the back to unscrew. You have to cut wires to remove the baseplate, then unsolder more to get the amp module out. Fergit about easy probing with a scope whilst runnning! What were they thinking*?
At this point the temptation to take the speaker out, shine a torch in to look for the relay and give it a good tap before cycling it a few dozen times is high!
*The service manual is an oddly specific combination of specific instructions for dealing with known faults and arm wavy faff that suggests bar those you give up and throw it in the skip .
But the bad luck is that, even if it was, this was not a unit designed for servicing. No plate amp on the back to unscrew. You have to cut wires to remove the baseplate, then unsolder more to get the amp module out. Fergit about easy probing with a scope whilst runnning! What were they thinking*?
At this point the temptation to take the speaker out, shine a torch in to look for the relay and give it a good tap before cycling it a few dozen times is high!
*The service manual is an oddly specific combination of specific instructions for dealing with known faults and arm wavy faff that suggests bar those you give up and throw it in the skip .