weird effect blew up my amp??

B

baniak

New member
Disclaimer: I am not a complete idiot, despite what my actions might say about me.

So, I have had this Behringer KX1200 keyboard amp/PA thing for about 9 months, and it's worked pretty nicely. Until yesterday.

Yesterday I received this kind of rinky-dink Realistic stereo reverb system (radio shack reverb thing) in the mail (I got it off of ebay.) So, I plugged it into my amp using some RCA cables from the Main out section of the reverb unit into the tape-in part of the KX1200 - then I plug in an acoustic guitar with pickup into the 1/4" microphone jack of the reverb thing.

No problem, it works well (as well as a rinky-dink reverb thing could be expected to work) and I'm jamming away - so I decide I want to record it by plugging it into my mixer (Behringer Eurorack mx802) so I connect the amp to the mixer, with an unbalanced 1/4" jack, except - because I am too lazy to use the main out on the back(and because it was late and I didn't want to wake anyone up) - I decide to run the 1/4" jack from the headphone out of the amp, into the mixer.

Oops - now the amp doesn't work... like it's supposed to.

Now I turn on the power and the power light flicks on for 1/2 second, and the shuts off, and instead of working, a hum comes out of the amp - the hum is a "B" an octave and a half step below middle C is this helps the diagnosis. The headphone jack still works, because when I plug in headphones, the hum stops coming out of the speakers, and instead comes out of headphones. Oh yeah, the hum comes out even when master volume is turned all the way down.

When I plug an instrument into the amp - nothing happens, just the same old hum - no instrument sounds whatsoever. The hum does not respond to the master volume control, only in that it started "fluttering" when I turned the volume all the way up, but the volume didn't change.

Okay, here's the weird part - if I play something using that rinky dink reverb box plugged into the tape in of the amp - then I can hear stuff - instruments, etc. So, apparently they tape-in of the amp still functions??

So, any ideas about what the hell's going on? I'm asking you guys first because I am too embarassed to explain this, plus I'm sure that I have not kept the receipt for the amp, and I'm sure my stupidity has long ago voided the warranty anyway.

You think this thing can be fixed?

Thanks...
 
The headphone jack is a normalled type connection, meaning it's normally routing the audio to the power amp section. When you plug in a set of headphones, it breaks that connection and sound only comes through the headphones. Possibly the jack is bad and when you remove the headphone plug it doesn't close any more so no output. Just a guess.
 
If what t-rat says is true, turn everything off and try plugging the connector in and out of the socket a few times to see if that releases it.
 
thanks for the replies

I'll keep trying the plugging and unplugging the connector trick - but for now it doesn't seem to be working.

Thanks for the ideas though. Anybody else have suggestions?
 
yep

Yep, but I still paid for it, so I want to get my $3.62 worth ;)

In reply to DJL, I think I misunderstood what you said, I am now goofing with the headphone socket and pluggin/ unplugging it, I will let you know how that goes.
 
Along semi-similar lines:

Would sending a signal from a headphone jack (on a regular cd player or laptop) to a monitor amp via a Y-cable (1 stereo to 2 mono 1/4) be in anyway harmful to the amp?

Thanks,
T
 
I might try to see if I can finagle the warranty out of it at the music store I purchased it at. There's a small chance the receipt's still around here somewhere, so, that should make the whole deal alot easier.

Thanks all.
 
behringer kx1200

hey. i am having the exact same trouble with my behringer kx1200. the Low B hum no matter what happens. maybe the head phone jack does have something to do with it, plus i know i used my roommates peavey reverb unit with it, since it doesn't supply its own reverb.
what was your fix or conclusion? is it necessary to replace a ribbon cable? an imput? i'm not very familiar with green circuit boards...
i'm trying to fix this now. can you guys offer some input? Thanks in advance.


ryanatlarge@yahoo.com
 
Dude, I'm afraid this thread was over 5 years old before you resurrected it. I'm sure he's long gone by now.
 
old behringer prob

yeah, i caught the date a little bit late. but the thread never came to real conclusion. i bought mine of musiciansfriend a couple of years ago, and called them back when it started its new bad habit. i was 2 months too late on the warranty. they said i have to ship it to Germany for any repairs unless i know someone here that can do it.
interesting, though, you still caught me posting this so far into the "future". i will continue Googling the answer i need. i know i can fix this for cheaper than a German freight from north GA. i live in Athens, and it's one huge musical town. maybe there's still a wise techie around.. they keep retiring and dropping like flies, though.
 
ryanatlarge said:
will continue Googling the answer i need. i know i can fix this for cheaper than a German freight from north GA. i live in Athens, and it's one huge musical town. maybe there's still a wise techie around.. they keep retiring and dropping like flies, though.
Click to expand...

For an amp? You could probably buy a new one cheaper than shipping it to Germany.... :D

Does the amp work and hum or does it do nothing but hum? If it works and hums simultaneously, it's a bad ground, probably caused by a bad solder joint. If it doesn't work, the cheap Chinese supply capacitor probably blew out, delivering AC to circuits designed for DC, and that may very well have fried every transistor and/or op amp in the amplifier....
 
ryanatlarge said:
yeah, i caught the date a little bit late. but the thread never came to real conclusion. i bought mine of musiciansfriend a couple of years ago, and called them back when it started its new bad habit. i was 2 months too late on the warranty. they said i have to ship it to Germany for any repairs unless i know someone here that can do it.
interesting, though, you still caught me posting this so far into the "future". i will continue Googling the answer i need. i know i can fix this for cheaper than a German freight from north GA. i live in Athens, and it's one huge musical town. maybe there's still a wise techie around.. they keep retiring and dropping like flies, though.
Click to expand...

Gotta love your determination--good luck! Just pay heed to the post right above mine--consider what it's worth before moving heaven & earth to fix it.
 
It sounds like the design or construction of the amp is faulty. Using the headphones as you described shouldn't blow the amp.

You might also want to try a ground lift and see if that eliminates the hum. Behringer amps are a pile of steaming you know what, these kinds of problems are not uncommon.

I did a gig last year with a fellow that used a Behringer amp and it hummed. There was also some sort of other issue with it regarding sending a feed to another amp. A ground lift fixed the hum, but it was pretty clear the amp was junk. I think that person has a Roland amp now.
 
SonicAlbert said:
You might also want to try a ground lift and see if that eliminates the hum. Behringer amps are a pile of steaming you know what, these kinds of problems are not uncommon.

I did a gig last year with a fellow that used a Behringer amp and it hummed. There was also some sort of other issue with it regarding sending a feed to another amp. A ground lift fixed the hum, but it was pretty clear the amp was junk. I think that person has a Roland amp now.
Click to expand...

Never used a Behri amp, but my Marshall hums like a motherfucker, and I had to return it for repair 2 months after buying it coz the speaker had just randomly died. Came back from work one day, turned it on and nothing would come out except for a hum.

That's supposed to be the King of Amps :rolleyes:
 
ryanatlarge said:
i'm not very familiar with green circuit boards...
ryanatlarge@yahoo.com
Click to expand...

for the record the green are better than the brown... but operate identicly... no way to effectively troubleshoot this on-line... a tech needs to have hands on... and if real experienced maynot need a schemo for this(most of these kindsa things are way basic in most reguards... the biggest problem is berh uses mostly surface mount technology which gives some techs headaches...
 
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