Question about Behringer FBQ6200 Home Equalizer

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Grounding hum Even with nothing connected to the input, there is a grounding hum on both channels of the unit. I found a schematic, but it didn't include the power section. I suspect it's one of the capacitors but none are showing anything unusual on the voltmeter. I don't have access to an oscilloscope, so if someone has the schematic for the power section that would help alot!

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  • kingpin911 Oct 13, 2009

    Yes, it is 60Hz hum and I'm already aware it's a grounding problem. The power connector is a typical molex, and only fits one way. There is no power amp in the loop.

    What I need (and asked for) was if anyone had the schematic to the power section so I know what voltages to look for and can trace which capacitor is faulty.



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60 Hz hum? May have a grounding problem. can you turn the power plug around or is it a one way plug?Any ac or dc voltage between unit and control/poweramp?Can you ground unit? Check for voltage first.

Posted on Oct 06, 2009

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The FBQ6200 has got a traditional dual power supply built with two linear voltage regulators. These are positive and negative "three-pin" 15 Volts regualtors located on the input/output jack board. The regulators are of the well-known 7815 / 7915 series, mounted on the only heatsink you will find there. Check them, by the way, they are mounted with insulation pads.
The input and putput amplifiers are built with S4580 dual-Op-Amps and are frequently destroyed by hot-plugging the input/output cables.
Remeber: The appliance has symmetrical or so-called balanced input/outputs, but not with real transformers and therefore real isolation. The input/outputs are electronically balanced (and unbalanced) with these op-amps (integrated circuit, search them in the web), and these ICs do not withstand static electricity.

Posted on Jan 18, 2010


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Hum when mixer is turned on

If it is a 60Hz or 120 hz hum, the fault may be a bad solder connection to a filter capacitor in the power supply.

If it is a hum like a bad mic connection, you may have dirty contacts on an input, dirty tracks on a mixer control, even on the EQ portion.

It may also be a bad cable is connected, or a 1/4 inch jacked input may not be grounding out when the plug is removed. You may have a bad ground on the power feed and you have a ground loop as a result, or a cable is faulty and creating it's pwn ground loop to something else.

Contact cleaner is not a bad idea, slide pots are notorious for spurious noise over time. LPS1 is not bad, but it does use silicone as the dry lubricant portion.

If all of that is ruled out, look internally for bad solder joints- anything that looks crumbly is suspect, and also check for loose wires and jacks with bad solder connections. Also look for loose connectors too.

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I have a Boston Acoustics VR-500 Subwoofer with a problem. As soon as anything is plugged into the line level RCA jacks, the subwoofer produces a loud buzz/hum. I have tried connecting it to the subwoofer...

I'm thinking you have an open shield ground on the RCA input side. Connecting speaker inputs possibly restores the ground. Try connecting the high level inputs then disconnect the remote end of the cables (floating the grounds).

Then get out an ohmmeter and find that open circuitor or bad solder joint between RCA ground and real ground in the speaker's amplifier. Or.... if speaker ground kills the hum and you want to use RCA Line Level input to the sub, just connect one minus speaker output on your source amp to one minus on the sub's amp.

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i had the same problem once and in my case i had accidentally used ground wire for signal. pls check ur connections again. one check u can do is set the high pass filter to 70Hz and see if that cuts out the low hum.

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My home theater speakers make a constant hum whenever my receiver is on. The loudness of the hum changes with the volume control, and goes away entirely when the system is muted. All components are plugged...

Sounds like a grounding issue. The first two places to look into is the powered subwoofer and antenna. During your last test, did you leave the FM antenna and subwoofer connected? Many times the hum is directly related to the antenna and/or the subwoofer and to how they are grounded; creating a ground loop through the receivers ground on the outlet. If the antenna is grounded to the dwellings wiring, hum is inevitable and sometime you can get a ground loop hum from how or how & where the subwoofer is grounded. Try taking them completely out of the loop.

Also try taking it further back to the basics, start with the receiver plugged into a known good grounded outlet with no surge or line conditioner in the loop and nothing connected to the receiver, nothing. Use one speaker and different wire to test each speaker output while in tuner and any other mode but phono. With no signal, you will either get nothing (no hum or static) or just static in the tuner mode. No hum is a good sign. Some systems will mute the speakers if no signal is connected to eliminate the static from being produced through the speakers but a ground loop hum will most likely still be produced even in mute. If you get a hum when nothing is connected to the receiver, try looking into getting a better grounded outlet, even maybe to a different dwelling.


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If the problem not the turntable but other component i.e;DVD,CD or cassette ,please check your stereo cables that one of them-even one channel, L or R - could be broken/damaged and should be replaced..MAke sure to replace one by one to localize the broken cable..good luck...

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Major feedback hum from speakers

The reason for the hum is as follows:

1) The phono input on the receiver contains an additional stage of amplification required for typical turntables.
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3) Your turntable contains an pre-amp that allows it to work using an aux input (or tape input) as most receivers today no longer have phono inputs.
4) Grounding issues relate to the older types of turntables where there was NO pre-amp stage inside the turntable. In this case ,the signal levels were so low that stray noise would often get in the way of the signal. Proper grounding would elimiate this noise.

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Good luck;

Dont forget to rate...


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