Behringer MX 1602 audio mixer diagnosis - bad power supply design
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- Опубликовано: 16 апр 2022
- This audio mixer had problems - all because of a badly designed power brick.
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This video made me hug my made in USA Mackie 1202. Flawless performance for over 20 years.
I still have my 1604 vlz, countless gigs..tho it could do with a major overhaul now.
You know you have a good channel when the video is just root cause analysis/explanation with no actual bench work and I still watch the whole thing. I have a behringer DJ mixer now and can attest it’s a POS. Have to use external phono preamps because the ones in the mixer sound terrible and believe me, I am not some kind of audiophile. Great video my friend.
Thank you :)
A full repair video would have been painful to watch, it took me about 2 hours of testing and searching to finally notice there was something wrong inside the power brick...
@@DrCassette perhaps also some foul language (in German)
No, there wasn't any of that, but lots of confusion :)
The Caps on the power supply on these behringers usually fail... good idea to replace them as you said...
1) I guarantee the case will be a better heat sink than the ones you attached. 2) 70C is not really very hot, not for power semiconductors. 3) 18.5 is open circuit. Rectified and under load you are maybe 24V. You used 12V regulators. They would have 25% higher temperature rise versus the proper 15V versions.
I wonder if even audio electronics couldn't get away with properly filtered modern DC-DC converters running at high switching frequencies these days, or at least switchmode into LDO regulators to cut down the excess heat. (edit) OK, maybe we shouldn't let Behringer do that, they can be surprisingly dumb when trying to separate digital from analogue circuitry...
The transformer specs are trite either way, in "Europe" you can get anywhere between 217 and 253V (230V +/- 10%) from the wall which will directly translate into transformer output voltages. In this application, the only relevant aspect is that the rectified DC on each rail needs to be above the drop-out of the regulators and below the limits of any intermediate electronics (mostly smoothing capacitors and cooling).
Oh Berhinger…. What can I say about this brand: It’s a Xerox machine. Literally. They copy a lot of designs from other manufacturers and built them cheap. I’ve got a small Behringer USB mixer that still works, but they are known for quantity issues. Their stuff is cheap and cheerful as long as you get a good unit.
Yes, Behringer does not have the best reputation - and after seeing the problems this mixer has, I can understand why.
I did the same under volting trick with the SEGA Mastersystem-2 console, I replaced the dead 10V-DC wall wart with a switchable, 7.5V were still good, just the sound not as loud & far less heat, no other modifications
Hi - Great Video and Info. Yep I had the same problem with my behringer DJ mixer DJX700 one week after I bought it brand new. The right side of the case got very hot and the mixer became unstable. I got a refund. But I see lots of faulty Behringer mixers on the market for sale and most of the description refers to unit getting hot. No quality testing and or bad design. I never bought another behringer product since then. I've heard bad reviews about them.
Wow... Just knowing the required voltages on the wires to the chassis is tremendously useful. It's almost worth designing a different, completely linear supply that delivers those voltages, keep it outside of the main unit--a 120 or 230 VAC transformer for the linear regulators will be too big to fit inside anyway--and shield the heck out of the (keep them short) DC voltage leads into the main unit. Oh... and throw some small ferrite beads around the DC leads and even the mains cable conductors. Of course, you would be doing all of this for a Behringer-designed mixer... Hmm...
Reminds me of how every polk powered sub dies just out of warranty.
Older Behringer mixers are also known for caps in the signal path going bad (47µ if memory serves), so perhaps spot-check some of those while the unit is apart. These are a major reason for the reputation of Behringer as being noisy.
I can only imagine that the power brick was originally designed to be used for a +/-18 V supply, but then Behringer went to 4580s which really shouldn't be run at more than +/- 15 V. 2x 20V~ secondary would be something like almost +/-27 V= rectified, so that's a lot of voltage wasted even under worst-case conditions. Not using more than an absolute minimum in filter capacitance may have been another deciding factor... perhaps have a look at ripple on there post-repair.
It is normal for transformers to reach specified secondary output voltage at maximum rated output current. I've had a nominal 12 V= router power supply that would output something like 15.6 V unloaded.
And yes, putting a fuse in the center tap is one of the most asinine things I've seen. 🤦 It's not like you couldn't get 100/125 mAT fuses suitable for the primary or anything.
Thank you for the info! :)
I have a 1604 that only has stereo sound out the second outputs. Right main works and left is quiet. Leads me to believe its isolated to just that left channel as if the whole left wad blown, the second outs wouldnt work.
This is a 1990's era mixer. I'd be curious to see if the new one's have the same design flaws? I have a Behringer line mixer, a year or two old that works fine. It replaced a Samson SM10 that started blowing fuses.
i like you very straight forward😊
Thank you for providing such a clear explanation. I’m troubleshooting a similar age MX1604A, if I’m measuring resistance when checking the power supply, can I assume the fuse is working? Measuring 1-2 4 ohm 1-3 5.5 ohm 2-3 4ohm, and seeing voltages at 19.6VAC. Do you have the part number for the 15VAC transformer you decided to swap with, if I decide to follow your path to lower heat output? Thanks in advance
You have continuity between all connections of the power brick, so the fuse is fine. If I swap the transformer, the replacement will be a suitable transformer salvaged from some other device.
At Behringer the price makes the music. Cheap prices for the product seems to be successful with small calculation in the electronic parts. You are on the right way to make the product better but will Behringer do it actuel in their newer products ? I don`t think so. I had a mixer 802 and it had after serveral usage problems wiith the heat, too and something go wrong inside, too. Thanks for your videos.
I have a 2004a and there is a tip29c for what i thought was phantom48+ but that uses a lm317???
That's kinda nasty how the fuse was on the ground line! A toroidal trafo would probably improve the noisy too. The LM7915/LM7812 notorious for running warm. thanks for the video btw!
The type of transformer is not that important as it is external from the mixer. Toroidal transformers indeed have less stray magnetic field, but with the power supply well away from the mixer, that won't really make much of a difference.
@@DrCassette True enough. I bought one second hand two weeks ago for 50 euros. The guy said it was working perfectly but he failed to ship the power adapter with the mixer - Doh. The low voltage plug I would need if I build my own one. How standard are those plugs?
Very informative video..Can someone suggest how to check the power supply without opening by means of a multimeter or something?
You can measure the continuity of the transformer windings at the output plug, so you don't need to open the power supply.
I have a theory that the cap didn't blow up at that high voltage because they may be using same can for multiple voltage rating/capacitance ratios, only difference being forming voltage.
I think this because i see old high voltage electrolytics sometimes being over 2 times bigger than their modern counterparts.
"Old" electronics can be surprisingly bad. Technology isn't all about cutting cost, there were some real advances in materials and production too. Now sure, an old quality cap (that hasn't leaked) may still be "fine" (if you like high ESR) compared to the Cheap Chinese Whatever you will likely find in most devices, but name brand products with the same specifications will be smaller and better.
I have the same problem with this mixer, which has been sitting here for a few years, "repaired" but still not working correctly. I replaced the blown fuse in the power supply and a capacitor, but there is still humming noise on all channels. Probably the capacitors have been damaged, as you have described. There is nothing visible on the outside, neither brewing nor cracks. I wonder why they didn't use a fuse on the primary side.
30.11.2022:
Damage pattern: strong hum = smoothing capacitor defective?
Summary: The smoothing capacitor C56 (1000uF, -15V regulator), which beside is only half of what the standard application (2200uF) suggests, had exploded and the glass fuse for the center tap in the transformer was defective. After fixing the 2 defects (one fuse now primary side of the transformer), the mixer should have worked again, but when unsoldering the old capacitor, a through-hole via was torn out, and it made no contact. There were unexplained voltages on the negative voltage regulator, which was fine, but was operating out of spec. Since the diodes were ok after the test, the fault had to be with the circuit board tracks. The leaked dielectric attacked the copper, and thus the via became unstable. Let's see how long it works again.
Conclusion: I have the suspicion that the capacitors are too small, which can also be heard from the small but existing ripple voltage (full gain) on the mixer, beside another serious issue to which I will come later. Larger capacitors would not have fit into the case. It could also be the reason for the hot regulators, because of stress. Furthermore, there is probably another risk with the voltage multiplier circuit for the phantom power, which in my case generates 78V (4 x 20V-voltage drop diodes) for the LM 317 (HV?). They branched off from the symmetrical voltage part. This is the only way to explain the high voltages on the caps after loosing ground potential. I wondered where these high values came from. It's quite complex with one after the other issue.
I would say that savings were made in a targeted manner in order to give this device a not too long life span, because after all, a company always wants to sell new products and maybe more expensive products, which hum less and last longer.
The other serious issue: The mixer was repaired once before in 1997 (MUSICSTORE workshop) due to an exploded capacitor shortly after purchase and worked about 15 years until next failure. Behringer provided a risky 3-pin device connector that should be screwed tight before plugging in an AC power connection, but I didn't always do that. If you turn it on with the device connector plugging in, there is random contact of one of the 2 voltages (2 x 20V~) or center tap (used as ground) and the circuit is in an undefined state!!! I'm sure a lot of people remember this. It made negative headlines for Behringer at the time, besides the Mackie design copyright issue. The leaked dielectric from back then could also have been the cause of the attacked circuit tracks. So the whole thing is already a very long story. Moreover, defective capacitors in the power supply due to aging or stress are a common issue in all electronic devices, even if Behringer has built-in an "early aging risk" here.
I hope this information helps as I had always hoped to use this mixer again even though I have already bought a new one. And yes, it was another one from Behringer, the XENYX 1002FX, which has been working perfectly for 10 years now with an 230V~ manual switch!
www.synthxl.com/behringer-mx-1602/
It is kind of funny but Behringer instructions say to plug the power cable into the mixer first, then plug the supply into the wall. To never plug it into the mixer if it is already in the wall lol. I wonder if they added that instruction after people reported problems ?
@@jrg770 No, that was really intended from the beginning. The thing is that the 2 voltages never came exactly at the same time when fiddling with the plug and that was stress for the electronics. 🙂
I received a old Behringer Eurorack UB1002 (not working) and it appears also to be this AC power supply Model MXUL3 (North America). 2x18.5 V @150 mA each. I opened up the casing and it does snot have a fuse. The voltages coming off the secondaries test at 21.3 volts. I do not know what is wrong with it however. When connected to the mixer, all the leds spike and eventually dim. There is a background noise in the audio signal that to me sounded like it could be a grounding issue. I hooked up my DC bench supply as +19V and -19V and ground to the power jack and the mixer is working fine. No Led issues, no noise. So is that strange ? To run a DC bi polar supply when the unit is expecting this dual 18.5V AC ? My solution will be to get a 18-0-18 1A transformer and see if that works. Nice video !
Thank you :)
Be careful. Related to the schematics of MX 1602 is the regulated output voltage +/- 17 volt (not +/- 15 volt). There is a 1N4002 between 7815 pin 2 (and 7915 pin 1) to ground. The minimum input voltage (without the 1N4002) for the 7815 is 17.5 volt. I expect a minimum input voltage of 19.5 volt for a output voltage of 17 volt!
Sorry for my bad english.
Thanks for the info, I will have to double check the schematic I have.
can i buy a power supply for this mixer? i have the same mixer and i cant find a power supply to buy
I m sitting with this same exact problem..mx 1602 from the 90s, still works. Albeit some noise on the 4 mic channels. The chassis gets insanely hot. Would It be a bad idea to add a high power 10 W / 15 ohm power rezistor on each 18.5 V rail, in the power supply, along with a 1.2 Amp fuse on each output . Our AC current sometimes peaks around 234V AC at the wall outlets. By my calculations it will drop each side ( plus minus 22.5V to 18 V ) which brings it into spec. Have i calculated this correctly?
I don't have time to double check your calculations, but some correctly dimensioned power resistors will help protect the device by dropping some of the voltage, this is correct.
Putting the rectifier circuit and voltage regulators on the unit seems likely to induce AC hum. Why on ground (earth) wouldn't they have used a bi polar (symmetrical) power supply?
They are using a symmetrical power supply, that's what the 7815 (+15V) and 7915 (-15V) regulators are for.
If you use an outboard power supply you have the same problem and on top of that you can couple in line noise even better since you're shipping your "clean" supply voltages through an antenna. By having a primitive inefficient linear supply inside the case, you can shield it all in one go.
Hello .. I bought a behringer eurorack mx 802a on eBay without powersupply... Based on research the powersupply thst comes with it is 18v for 2 of the pins (xlr) at 800 mah.
However the powersupplies being sold on eBay for it is 17v for 2 pins at 600mah... Can those eBay power supplies work?
This should work, but you have to be sure that the connector pins are in the right order. You need 2 x AC (originally 2 x 18V~) and ground, similar to the MX 1602. If the vendor offers it for this mixer, it's fine, as long there are no other issues like blown up capacitors in the mixer itself. The 1V difference isn't a problem and should keep the mixer a little cooler.
@@Klangraum thank you
@@Klangraum i think its a generic powersupply on ebay... Not sure if it was specificslly made for that model so to speak.. Its like replacing your phones USB charger cable with another generic one.
I love Behringer
What are the signs of a blown fuse? As the mixer still works it must be hard to discover a blown fuse.
I finally discovered the blown fuse when I measured resistance between the output connections of the power brick. Since the power brick outputs AC, it should be possible to measure the resistance of the transformer windings, but I wasn't getting any connection to the center tap. So I then cracked open the power brick and found the blown fuse.
@@DrCassette Thanks. But, a blown fuse isn't an "ordinary" user will discover, Specially if they don't have the skills or equipment to measure it.
How will this error show up to an "ordinary" user? Will the unit work as intended? Any risk of electrical shock? Just a very warm mixer?
/Olle in Sweden
PS. Thanks for great and informative videos. ;-)
The initial symptoms were:
- Power LED turns on and off randomly
- Mixer does not pass any audio
- Occasionally there is a loud hum in the output, which changes frequency and then disappears again
So it will be very clear to the user that there is something wrong with the mixer. There is no risk of an electric shock.
@@DrCassette Thank you so much!
Now it is totally clear to me. ;-)
Keep up your great work!
Is there a follow up video?
No, not yet. I still haven't finished the repairs...
Well cheap mixer.....HUGE PROBLEMS.....it is like ....drink cheap wine/beer and of course feel sick!!! Anyhow.....thanks for your upload video DrCassette !!! Keep it like that !!!
hi there's mini 8 reel to reel brannell it had a bad power unit the same thing the power reg's were over heating re made the power unit
step down to 45 dc and ad on alot more reg's now it has the high volt lm317 one's to power the audio cards
it was allways blowing the power unit fuses all he time
soundcraft decks are the same no fuse's in the power units 381-8 is very bad for over heating
What is this for a creepy mixer and no actual power supply that is in an apartment or on stage not funny if the mixer begins to burn ):
Horrific design decision