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Subwoofer cuts out

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Subwoofer cuts out

Postby northflow » Mon Jan 06, 2020 11:47 pm

So ive had this issue with my subbwoofer that its randomly stops sending out any sound.
it can be dead for a day or two and then suddenly just starts working again.

Something strange that ive discovered is that it often dies when it gets alot of bas thu the inputs. even stranger is when i put on some music with much bass and crank the volume it can make it start again. like a defibrillator can both kill and start a heart.

tested with different soundcards & computers.

Best Regards Mattias
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Re: Subwoofer cuts out

Postby Hugh Robjohns » Tue Jan 07, 2020 12:34 am

Your description is suggestive of a dry joint somewhere in the signal path...
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Re: Subwoofer cuts out

Postby northflow » Tue Jan 07, 2020 1:38 am

interesting, how come it work sometimes depend on the signal strength then?

note that the satelites still work and they go thru the subwoofer.

Thanks for response!
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Re: Subwoofer cuts out

Postby Hugh Robjohns » Tue Jan 07, 2020 12:32 pm

A 'dry' solder joint causes the circuit connection to go 'high-resistance'. The same thing can happen with corrosion on connectors, including the connectors between circuit boards. Owners of older Mackie mixing consoles will be very familiar with this effect....

When sending a very loud signal, the signal voltage reaches a sufficient level to temporarily break down the corrosion and allow the circuit path to work properly for a short while.

If you are a competent electronics technician (and the unit is out of warranty), then dismantling the unit, checking the solder joints around the input circuitry, and cleaning any connectors with the appropriate materials will probably fix the problem.

If not, it will need servicing by a competent technician.

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Re: Subwoofer cuts out

Postby northflow » Tue Jan 07, 2020 1:58 pm

thank you, where do i locate the input circuitry on the board?
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Re: Subwoofer cuts out

Postby Hugh Robjohns » Tue Jan 07, 2020 2:06 pm

No idea... you'll have to look at where the input connectors are on the board, or the wiring from them to the board. But in all honesty, if you need to ask you're not (yet) competent to do the job.

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Re: Subwoofer cuts out

Postby northflow » Tue Jan 07, 2020 2:18 pm

Ok i understand. thanks for the help!

Best regards
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Re: Subwoofer cuts out

Postby northflow » Tue Jan 07, 2020 4:29 pm

update:

the standby switch is measured ok.

the satelite speakers remains low cut though sub when its not working.

Scenario:
sub is out. i gain low frequencies thru sub and it starts with a pop.
a strange dissonant noise comes from it.
when i gain the volume it continues but when i then lower the volume, the noise dissapears.
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Re: Subwoofer cuts out

Postby Hugh Robjohns » Tue Jan 07, 2020 4:50 pm

The high-pass filtering is probably on the input circuit card. So the inputs will go to that card and be split, with the signal going to the filters and then out to the satellite connectors, and also to a mixer to feed the sub amplifier.

If the satellites are always okay, the problem will be with the mixer stage or something after it.... which narrows the problem circuitry down a bit.

Again, I'd be looking for dry solder joints or corroded board connectors. If everything looks okay the next stage would be a proper investigation with an oscilloscope to find the point where the signal disappears.

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