BEHRINGER EURORACK UB2442FX-PRO Problem/Repair
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From: jonas_me on 5 Jan 2007 13:03 To anybody that might also have this problem, I thought I'd share what I did to resolve it. Let me preface the conversation on why I wanted to use this piece... This EURORACK UB2442FX-PRO is an ultra-cheap mixer (possibly the only one I am aware of) that has 10 real mic pre's for about $300. I use it for a rehearsal studio application, and I use inserts, aux sends and all that stuff, and this does it. This mixer develeoped a problem for me where microphone inputs would cut in and out and gain control knobs sometimes didn't work. Frustrated and being out of warranty, I took it to a repair shop to see if it could be something simple as a bad connector inside. I thought I'd let them trouble shoot it since i don't have the time to spend an entire afternoon taking it apart and looking at it on a scope. They told me that it had input op-amp failures and some of them needed replacing, and their labor costs would exceed the cost of the mixer. Now that I had an idea of what was wrong, I put it on a bench and starting checking all of the input op-amps. Indeed some looked bad, and I noticed some DC offset on the output stage also. Being that I work for an audio manufacturer, we happened to have OP275's in surface mount laying around, so I changed all of the input op-amps and it fixed everything. The Behringer input op-amps are JRC4580, and very cheap. The OP275 is a drop-in replacement and worked perfectly. No added oscillations from the new OP275's either. This whole repair took me about an hour with a proper surface-mount de-soldering heat source, a high-quality soldering iron and a magnifying glass. I left one good old JRC4580 in place to see if I could hear any difference from the cheap one versus the higher-end pro-audio one. And, as far as a 58 through a high-end PA system, there was really no difference that I can tell. Maybe with headphones and a high-end recording you might be able to tell, but I have a feeling since all other op-amps in the mixer are still JRC4580's (about 50 more of them), that the little upgrade in the pre-amp may not make much difference. J
From: tbmoas58 on 5 Jan 2007 13:23 <jonas_me(a)yahoo.com> wrote in message news:1168020231.869947.106170(a)s34g2000cwa.googlegroups.com... > To anybody that might also have this problem, I thought I'd share what > I did to resolve it. > > Let me preface the conversation on why I wanted to use this piece... > This EURORACK UB2442FX-PRO is an ultra-cheap mixer (possibly the only > one I am aware of) that has 10 real mic pre's for about $300. I use > it for a rehearsal studio application, and I use inserts, aux sends and > all that stuff, and this does it. > > This mixer develeoped a problem for me where microphone inputs would > cut in and out and gain control knobs sometimes didn't work. > Frustrated and being out of warranty, I took it to a repair shop to see > if it could be something simple as a bad connector inside. I thought > I'd let them trouble shoot it since i don't have the time to spend an > entire afternoon taking it apart and looking at it on a scope. > > They told me that it had input op-amp failures and some of them needed > replacing, and their labor costs would exceed the cost of the mixer. > > Now that I had an idea of what was wrong, I put it on a bench and > starting checking all of the input op-amps. Indeed some looked bad, > and I noticed some DC offset on the output stage also. > > Being that I work for an audio manufacturer, we happened to have > OP275's in surface mount laying around, so I changed all of the input > op-amps and it fixed everything. > > The Behringer input op-amps are JRC4580, and very cheap. The OP275 is > a drop-in replacement and worked perfectly. No added oscillations from > the new OP275's either. > > This whole repair took me about an hour with a proper surface-mount > de-soldering heat source, a high-quality soldering iron and a > magnifying glass. > > I left one good old JRC4580 in place to see if I could hear any > difference from the cheap one versus the higher-end pro-audio one. > And, as far as a 58 through a high-end PA system, there was really no > difference that I can tell. Maybe with headphones and a high-end > recording you might be able to tell, but I have a feeling since all > other op-amps in the mixer are still JRC4580's (about 50 more of them), > that the little upgrade in the pre-amp may not make much difference. > > J > Thanks for the info well beyond anything I would do but interesting none the less george
From: Eeyore on 5 Jan 2007 14:19 jonas_me(a)yahoo.com wrote: > To anybody that might also have this problem, I thought I'd share what > I did to resolve it. > > Let me preface the conversation on why I wanted to use this piece... > This EURORACK UB2442FX-PRO is an ultra-cheap mixer (possibly the only > one I am aware of) that has 10 real mic pre's for about $300. I use > it for a rehearsal studio application, and I use inserts, aux sends and > all that stuff, and this does it. > > This mixer develeoped a problem for me where microphone inputs would > cut in and out and gain control knobs sometimes didn't work. > Frustrated and being out of warranty, I took it to a repair shop to see > if it could be something simple as a bad connector inside. I thought > I'd let them trouble shoot it since i don't have the time to spend an > entire afternoon taking it apart and looking at it on a scope. > > They told me that it had input op-amp failures and some of them needed > replacing, and their labor costs would exceed the cost of the mixer. > > Now that I had an idea of what was wrong, I put it on a bench and > starting checking all of the input op-amps. Indeed some looked bad, > and I noticed some DC offset on the output stage also. > > Being that I work for an audio manufacturer, we happened to have > OP275's in surface mount laying around, so I changed all of the input > op-amps and it fixed everything. > > The Behringer input op-amps are JRC4580, and very cheap. The OP275 is > a drop-in replacement and worked perfectly. No added oscillations from > the new OP275's either. > > This whole repair took me about an hour with a proper surface-mount > de-soldering heat source, a high-quality soldering iron and a > magnifying glass. > > I left one good old JRC4580 in place to see if I could hear any > difference from the cheap one versus the higher-end pro-audio one. > And, as far as a 58 through a high-end PA system, there was really no > difference that I can tell. Maybe with headphones and a high-end > recording you might be able to tell, but I have a feeling since all > other op-amps in the mixer are still JRC4580's (about 50 more of them), > that the little upgrade in the pre-amp may not make much difference. The 4580 is actually a pretty good op-amp designed specifically for audio and with a better spec than the ubiquitous 5532. I'm sure you must have an idea what the mixer would cost if it had OP275s instead ! I'm very surprised at this fault. If it's only the mic stages affected it suggests a design flaw rather than a poor batch of 4580s.. Graham
From: jonas_me on 8 Jan 2007 12:49 You may very well be right about that. I was never able to acquire a real schematic though. It certainly is possible that something could have damaged it, spike on the input, or something else out of the ordinary. I asked around some of the audio dealers if they had heard of this problem from anybody else, but it appears that becuase these are so cheap, that it becomes a throw-away item, and not likely to be repaired. If anybody does have the schematic for it, I would appreciate a copy of it.
From: tbmoas58 on 8 Jan 2007 12:52
<jonas_me(a)yahoo.com> wrote in message news:1168278596.157764.177330(a)i15g2000cwa.googlegroups.com... > You may very well be right about that. I was never able to acquire a > real schematic though. > It certainly is possible that something could have damaged it, spike on > the input, or something else out of the ordinary. I asked around > some of the audio dealers if they had heard of this problem from > anybody else, but it appears that becuase these are so cheap, that it > becomes a throw-away item, and not likely to be repaired. > > If anybody does have the schematic for it, I would appreciate a copy of > it. behringer only releases schematics to thier authorized service centers george > |