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Old 25th July 2011, 03:49 AM   #1
rumble is offline rumble  United States
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Default behringer mx9000 - psu problem? or other?

i did the psu upgrade lst year and everything was fine until last night when i lost all the mute & solo leds on the board.

does anybody know if this is possibly still related to a psu problem or something
else in the board?

mixer still seems to function and i still have a meter bridge.

psu status lights on the mixer show -17v & +17v both on.

any help appreciated!!

rb
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Old 25th July 2011, 05:23 PM   #2
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I'm unfamiliar with the PSU upgrade, was it just replacing the regulators and associated subcircuit so it can handle more current? Pictures or a description of the circuit as much as you can trace it might help.

Are those LEDs always lit to some extent or are they driven by IC pins completing the circuit? If the latter, replace that IC if you can't find another fault. You might also try applying 2VDC regulated across LED anode + and cathode - to see if it lights up.

My initial guess is there is a current limiting resistor to the LEDs that has burnt through, failed to an open circuit, or a trace delaminated and broke, OR a power surge fried the LEDs.

Examine the board, trace the circuit between power source and LEDs.

As for a PSU problem, if it is still providing the correct regulated voltage then that portion seems ok still, but I would measure voltages with a multimeter instead of depending on status lights to be sure.
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Old 25th July 2011, 05:26 PM   #3
rumble is offline rumble  United States
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i don't remember the details of the upgrade. i had a friend of a friend do it. i'll have to get someone to look at your suggestions and try them. i'm not a techician.

but thanks for the suggestions!
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Old 25th July 2011, 05:30 PM   #4
rumble is offline rumble  United States
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p.s. - there are a few threads on the behringer psu problems and solutions if you search on google.
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Old 25th July 2011, 06:18 PM   #5
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^ thanks, but it seems your friend would need to tell you and/or us exactly what was done, as there can be variations from what I might find searching google, and the friend seems a good person to ask to take a look at it if possible.
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Old 25th July 2011, 06:50 PM   #6
rumble is offline rumble  United States
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this is what he did:

replaced the regulators and associated caps with higher
>> >> ratings, so they can handle more current - just as a precaution. He
>> >> said at the time, the PS is a POS, regardless of what he tried to
>> >> improve. Just a poor design.
>> >>
>> >> He also cleaned and polished the contact points of the regulators to
>> >> the heat sink, so they made better thermal contact so they would
>> >> dissipate heat better, that is, run cooler, which is always good.
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Old 25th July 2011, 11:22 PM   #7
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Assuming it worked fine after that mod, nothing described would account for LEDs failing (or the circuit that drives them).

Get out a multimeter and measure the power rails to confirm they are at expected values, but since the meter seems to function still, if the PSU only outputs the two voltage values then the PSU seems ok.

If the PSU instead has other windings to provide power for other circuitry, this other portion of the PSU could be to blame. They could easily have built it either way, if you have a link to the schematic or good picture of the whole PSU subcircuit it could help.

You might also probe the LED subcircuit to see if you get a voltage on anode or ground continuity on cathode (depending on how the circuit is set up, probably one or the other.

Unless you find a clear description or picture of the subcircuit those LEDs are in, it could be difficult for anyone to help you unless they have repaired this fault firsthand.
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Old 25th July 2011, 11:31 PM   #8
rumble is offline rumble  United States
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worked fine for about a year after the upgrade/mods/repair.
the psu plug has 7 pins so it must drive other circuits.

the psu failure for this mixer is a pretty well documented problem but i have not seen anything about the mute or solo lights associated with the psu problem, and there are no schematics available as far as i know (which is much lamented about in the forums about the psu problem)

behringer mx9000 problems - Google Search

i will try to test the pinouts with a meter though and the leds
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Old 26th July 2011, 01:08 AM   #9
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I found what is supposedly the service manual for the MX9000... but it is downloading VERY slowly and not finished downloading so I may not get a chance to look at it tonight to know if it is even the "real thing", or if it is helpful. I found it here:

BEHRINGER MX9000 SCH Service Manual free download, schematics, eeprom, repair info for electronics
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Old 26th July 2011, 01:39 AM   #10
rumble is offline rumble  United States
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that would be the holy grail if it is. i don't see a link to download (even though i'm using firefox like it says)
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