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Thread: Behringer DDX3216 - Trying to repair, please help!

  1. #1
    Junior Member fznuk's Avatar
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    Behringer DDX3216 - Trying to repair, please help!

    Hi,

    Im new to this forum, so hi to you all!

    Im a producer/composer/engineer with a home studio setup using that wonderful Behringer DDX3216 digital mixer which does have its issues...but love it!

    A mate of mine also owns this mixer and has had a couple of major issues with it, mine, i havent had too many, but it has had a bit of a benny every now and then.

    I have them both here now, and since i have electronics experience from past jobs, it has been sketchy but still managed to repair most things with a few pointers from other electrical engineers. I hope to have the same help and luck here if possible?

    I have my friends DDX here and open to repair first, his often has the usual 'all lights on' problem but this has now been replaced mainly with just the main output master LED's staying on, no sound and unresponsive after being switched on for any given length of time.

    Doing the usual read-up on the net i have come to the conclusion that the capacitors on the PSU may need changing. I have purchased and replaced all the 1000uF & 2200uF caps on just the output filter stage but on power-up i got the same problem after about 15mins.

    I switched it off/on and still got the same.

    I opened the PSU again and decided to reapply solder to various points on the bottom of the board, unplugged ribbon cables, plugged them back in, then switched on but this time with the case open. It lasted a lot longer....but when i finally shut the case and switched the unit back on and off i got the dreaded 'all lights on' again

    Switching off and on didnt cure it, so i removed the PSU again and now checking the cables and ribbons again on the main boards, including each power connector.

    Now, would it be worth it to replace all the other caps on the PSU?

    Can i measure the voltages without load on this PSU without problems? and is this worth it?

    Since the problems occur only after time, or random 'all lights on' occurs occasionally, would this suggest a filtered voltage problem or heat/joint problem?

    Can the processor or any IC's work for one minute then not the next? Seems unlikely? but could be wrong?

    Are there any other troubleshooting tests i could do to narrow down the problem?

    I have two desks to fix. as i say, they work perfectly when actually working but have random glitches

    Any help would be greatly appreciated while i have one desk in bits at the moment

    Simon.

  2. #2
    Lifetime Member km6xz's Avatar
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    Replacing things randomly in this unit will be frustrating and expensive since it is a complex device. The power supply needs to be checked to find if a rail is pulled down, a common cause of this symptom
    There are supplies for +48, +/- 17, +/-8, +/-12, +3 and +5V. If you do not have all of these and clean, you need to find out why.
    What test gear do you have available? Working with a switching power supply requires a little caution working with the secondary and a lot of caution in how you make your measurements on the AC input side.
    This is a difficult unit to repair if your don't have a decent collection of test instruments.

  3. #3
    Senior Member Enzo's Avatar
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    Amen, don't throw parts at it, find out what is wrong.

    All peak lights on in a mixer is usually a sign that one of the analog voltages is missing, in this case one of those 17v rails.

    In my own experience with these, I often find a cable from the top panel to the bottom panel coming loose. Can't tell you which one, but on the top it plugs in about the center of the panel, probably 15 pins or thereabouts.

    Factory bulletin suggests C48 in SMPS dries out - 47uf/25v 105degree. I have indeed found that to be the case in some.

    Can the processor or any IC work now and not later? Of course. Any part can be intermittant. More likely is the solder to it. There have been complaints that some of the LSIs on the main board were not adequately soldered. Pain in the ass, but I have seen that.

    But always consider the broad picture. It is the SYSTEM that locks up, not necessarily one IC in it. Your processor may be getting a halt signal from elsewhere, and shuts itself off. A flaky power supply can certainly stop a CPU in its tracks. And all modern systems have a power-on-reset circuit, and that restarts the computer whenever powr is interrupted. However if power is glitched and returned too fast for the system to realize it went down, there will be no reset, and the system program can freeze.
    Education is what you're left with after you have forgotten what you have learned.

  4. #4
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    This unit was also prone to bad crystal oscillators and .1 decoupling caps.
    John R. Frondelli
    dBm Pro Audio Services, New York, NY

    "Mediocre is the new 'Good' "

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    Senior Member Enzo's Avatar
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    And as I recall a serious pain in the ass to take apart and extract the SMPS.
    Education is what you're left with after you have forgotten what you have learned.

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    Junior Member fznuk's Avatar
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    Thank you so much guys! and from a thread i read on here regarding this mixer, it was you guys i was hoping would reply

    You are right in not throwing random components at it which is why i only replaced output filter caps which i read from a thread on another forum, but with this not making any difference, together with pulling and replacing connectors, i decided to ask on here since your other replies on posts sounded like you guys knew this unit well.

    Im pretty competent with understanding electronics and with a bit of a brush up on circuits like switch mode power supplies im sure i can get my head around it but my main job is PC diagnostics so i don't come across too many component level repairs these days.

    I have a purpose built electronics workshop but my test gear is limited to an old Scope and multimeter.....then usual tool...and soldering iron. But the desk is pretty big so decided to open and fix on the kitchen table!



    I originally noted down all the caps on the PSU - i also noticed that its built up from three PSU's with various voltages. I was going to get all the caps but decided to try the output ones first, i will see if i have a spare 47uF to try!

    You also mention the crystals - are these Q1 & Q2 on the processor board?

    Thanks again for your help!

    I will keep you all up to date on if i fix it or not

  7. #7
    Junior Member fznuk's Avatar
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    Quote Originally Posted by Enzo View Post
    And as I recall a serious pain in the ass to take apart and extract the SMPS.
    I got to admit it wasn't too bad, was slow and apprehensive at first with all those ribbon cables, but after propping up the lid and removing the top lid connecting cables/PSU leads it was easy. Now a lot faster taking it apart and putting it back together! lol

    I have another one to do yet too! lol

    I think in future im going to dig out the scope and test properly, but my scope is a hand-me-down, old and maybe need re calibration?! Wouldnt mind one of these PC scopes now!

    Well, gonna try changing this 47uf cap and checking the analogue 17V rails as this cap is on the same PSU as the 17V supply..... what about the 1uF cap next to it?

    And, as i said in the last post, can i test this PSU without loads? Just like i can test a PC SMPS without load.

    Cheers again guys!

  8. #8
    Senior Member Enzo's Avatar
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    yes it should be fine without a load.
    Education is what you're left with after you have forgotten what you have learned.

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    Junior Member fznuk's Avatar
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    Quote Originally Posted by Enzo View Post
    yes it should be fine without a load.
    All voltage rails seem to be ok, before and after 47uF change.

    I have +48V (47.7), +&- 17V (16.8) and all the others. I dont have a decent scope as yet to see if there are any ripples. I have ordered one of those USB ones and decent 100KHz probe sets.

    Going to roughly put the desk together again and see how long it lasts before going haywire.

    I suppose i really need a scope to test the crystals too?!

    I also noticed a lot of noise from all parts of the circuit... primary and secondary? I suppose the transformers are badly wound? or the coils? - is a white noise sound that's quite loud?

    Maybe i should check the primary input filter caps (Large ones) and double check diodes, startup resistors and transistors?

    Cheers

  10. #10
    Lifetime Member km6xz's Avatar
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    Does the old scope work at all? If so, even if not calibrated it will be better for general pro audio use than a USB type which usually has limited bandwidth and low maximum input signal amplitude. An old Tektronix 465 100Mhz scope will cost about $150 and last 10 times longer and be more functional than a USB module.

    What noise, where, how did you measure it....I am confused. You already determine the supply is not causing the mixer to be locked up so move on to more logical causes. There are lots of crystals in the mixer, 24mhz, 12.xxxmhz etc. Your meter probably can't see that but you can see if data lines are steady state "1" or "0", by reading a DC level of some where between 5volts and zero volts.
    Where the supply voltages measured with the cables to the rest of the mixer installed or without a load? If no-load, try hooking up the ribbon cables and measure again to see if one rail is dropping out under load. If your measurements were with the load of the circuits, forget the supply and assume it works.

  11. #11
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    In an effort to help here, I just checked every DDX3216 repair in our database. Overwhelmingly, the solution we took to the problem described here was the replacement of crystal Q3, 32.768kHz. Over and over, the problem reads the same: runs for awhile, then locks up, no control, etc. Sure, there are also the ubiquitous cap issues and poor soldering, but this fits the bill. Hey, it's worth a shot. You need to eliminate this common issue first. We stock these crystals. Mouser has them as well, part# 559-NC38-LF.
    John R. Frondelli
    dBm Pro Audio Services, New York, NY

    "Mediocre is the new 'Good' "

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    Junior Member fznuk's Avatar
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    Quote Originally Posted by km6xz View Post
    Does the old scope work at all? If so, even if not calibrated it will be better for general pro audio use than a USB type which usually has limited bandwidth and low maximum input signal amplitude. An old Tektronix 465 100Mhz scope will cost about $150 and last 10 times longer and be more functional than a USB module.

    What noise, where, how did you measure it....I am confused. You already determine the supply is not causing the mixer to be locked up so move on to more logical causes. There are lots of crystals in the mixer, 24mhz, 12.xxxmhz etc. Your meter probably can't see that but you can see if data lines are steady state "1" or "0", by reading a DC level of some where between 5volts and zero volts.
    Where the supply voltages measured with the cables to the rest of the mixer installed or without a load? If no-load, try hooking up the ribbon cables and measure again to see if one rail is dropping out under load. If your measurements were with the load of the circuits, forget the supply and assume it works.
    hi, and thanks again to you all for help with this mixer! much appreciated!

    Yes, the scope does work:



    Its a Gould 12Mhz one.... given to me a few years ago.

    The USB one is just to have a play with really, and cheap so no love lost if its no good....well i will see when i get it!

    I have also ordered a Cap test meter which will help...i think! lol

    After brushing up on a bit more with regards SMPS, i feel i have learnt a lot since embarking on the mixer a couple of days ago. being absorbed into electronic reading material has never really been my strong point...more of a practical person....and occasionally blowing things up to learn type! lol

    The noise was always there, a kind of hissing, but seemed to get worse across the board?! I think coming from the transformers/inductors?! - But, on powering up the mixer with it (top wedged open and PSU without a lid) the desk fired up....and got a different light show..... but then a flash of sparks from the PSU area..... As i rushed to power off I noticed that one black PSU lead had dropped from within one of the PSU plugs going to the top back right of the console. I removed the white plug and reinserted the lead but when i plugged it back into the PCB it fell out again as the plug was inserted. This time i re-inserted the lead/pin and made sure it was secure........ plugged the desk back up and it worked a treat. I attached powered speakers and a sound source and left it on, i switched it off and on a few times (something this desk hated in succession) and removed the sound source 1/4" jacks and reinserted them, again, something this desk loved to 'crash' on, but it worked well for at least 2-3 hours.

    After this i removed the sound source and speakers, just about to remove the PSU to box it up and thought i'd just turn it back on again....bang.....i got the all the lights problem?!! I switched it off and straight back on.....the problem went away and the desk was back (something the desk hated when it got the lights of death as you would have to wait 20-30 mins to switch it back on).

    So... am i getting somewhere or going round in circles?! - i suppose this is where the scope comes in!!?

    In my line of work i dont usually need a scope and havent used one in a long time...but im sure its like riding a bike and my training will come back! and prob never put the scope down again!

    I do get electronically lazy at times but determind to fix this desk....the right way!

    And will probably get my head back into electronics books again to brush up on my old electrical repair knowledge!

    ...............shamei cant get as excited in getting back into music composition! lol

    Crystals - I will look into this as long as i know the PSU is steady as i tested it without load. So next i will check with load and see if any rails drop.

    Cheers guys!

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    Junior Member fznuk's Avatar
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    Quote Originally Posted by jrfrond View Post
    In an effort to help here, I just checked every DDX3216 repair in our database. Overwhelmingly, the solution we took to the problem described here was the replacement of crystal Q3, 32.768kHz. Over and over, the problem reads the same: runs for awhile, then locks up, no control, etc. Sure, there are also the ubiquitous cap issues and poor soldering, but this fits the bill. Hey, it's worth a shot. You need to eliminate this common issue first. We stock these crystals. Mouser has them as well, part# 559-NC38-LF.
    Thanks for that, but im in the UK so maybe i should have a look here and see if i can get the crystals for a decent price.

    One other thing, if the primary large caps were on the edge of failing, would this mixer work but cause lockups like this?

    With the scope i suppose i can check for ripples?

    Cheers!

  14. #14
    Supporting Member Jazz P Bass's Avatar
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    You can check Vdc for "ripple" wih a decent voltmeter.
    Set the meter to read Vac.
    Last edited by Jazz P Bass; 03-11-2011 at 02:47 AM.

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    Quote Originally Posted by fznuk View Post
    Thanks for that, but im in the UK so maybe i should have a look here and see if i can get the crystals for a decent price.

    One other thing, if the primary large caps were on the edge of failing, would this mixer work but cause lockups like this?

    With the scope i suppose i can check for ripples?

    Cheers!
    The crystal is made by Fox and their part# is NC38. You should be able to source it in the UK. It's a small watch crystal oscillator. Seriously, you NEED to eliminate this. I COULD be wrong, but according to our repair documentation, there's a good chance I may be right about this.
    John R. Frondelli
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  16. #16
    Noodle of Reality Steve Conner's Avatar
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    I definitely agree replacing the crystal is a wise move. Farnell should have one, but if you want to do it in real ghetto style, bust open any battery powered digital clock or watch, and take the 32.768kHz crystal from that. Old computer motherboards often have one too.

    Sometimes you can check a crystal oscillator with a scope. But other times prodding it with the scope can make it stop, so it appears faulty even though it's perfectly functional the rest of the time.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    Junior Member fznuk's Avatar
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    Quote Originally Posted by Steve Conner View Post
    I definitely agree replacing the crystal is a wise move. Farnell should have one, but if you want to do it in real ghetto style, bust open any battery powered digital clock or watch, and take the 32.768kHz crystal from that. Old computer motherboards often have one too.

    Sometimes you can check a crystal oscillator with a scope. But other times prodding it with the scope can make it stop, so it appears faulty even though it's perfectly functional the rest of the time.
    Cheers again guys!

    I will see what i have kicking about to try it before ordering new. Not had much chance to have a look over the past few days due to getting in a lot of PC work.

    I will get back to you all after i have replaced the crystal and done a long test.

    Cheers again!


  18. #18
    Junior Member fznuk's Avatar
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    Still Failing?!

    Hi guys,

    Bought and fitted the new crystal (Q3) but i still have the original error where after a random amount of time the master LED's light up full and you get no sound.

    One good thing is that you don't need to wait 20-30mins before you can switch it back on to clear the error?!

    My probes still havent come for the scope as yet so cant check for any power ripples etc.

    It will also crash at boot-up on the logo screen if switched on and off too fast.

    and since i still get crazy hi pitched noise from the PSU, almost like digital modem noise, but higher, im still wondering if the PSU is struggling somewhere or input Caps are bad on the primary?? I bought a Cap meter which will go up to 20,000Uf, and i know it isnt brilliant but will give me an idea.

    Would still love to fix this beast!

    Cheers again for all your help! and any more would be appreciated!


  19. #19
    Lifetime Member km6xz's Avatar
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    Sorry but replacing parts randomly or on advice on a web site often results in worse operation. Diagnosis the problem and fix that, not throw parts at the problem until it magically goes away.
    You have a very strong clue that no one is considering in the rush to replace a crystal. The power supply has a normal switching frequency of way above human hearing between 200khz and 1Mhz depending on the load. Did you try to isolate the supply or reduce the load to see if the supply is singing at a low frequency by itself or due to excessive load? A low switching frequency means very low transformer efficiency and more heat in the switching transistors, and lower output, higher ripple etc.
    What is causing the singing? The mixer or the supply not able to switch at normal rates? You do not need probes for testing DC output ripple level, but any measurements in high Z circuits do require the probes. So far, it appears that the most basic measurements have not been taken due to lack of gear. The supply performance should be isolated by testing on loads, without the mixer connected. From there, you will know where to look for the problem.
    The biggest problem is that you are attempting to repair a complex device that 80% of current pro techs would not even try to get into due to its complexity and lack of service information. Even the warranty stations had little more than a schematic and little other assistance. Behringer USA knew NOTHING about the unit, which was about 2.5 light years ahead of anyone's electronics knowledge at the US based distributor.
    When we were the warranty station for those, most of the repairs we did, were correcting problems induced by other Behringer warranty shops. There was no one to turn to for help so we reversed engineered much of it, and built test jigs for isolating different pc boards and the supply. That is what it took to successfully repaired hundreds of them.
    Starting a repair career on a complex digital board is not going to be easy unless a basic problem with the supply, or a shorted bypass cap is found. I think you would be better off sending it to a shop that has built up a reputation for being experts in these, it will probably be cheaper and a lot less frustrating.
    Good luck

  20. #20
    Noodle of Reality Steve Conner's Avatar
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    Good point, a SMPS in a piece of pro audio equipment should not squeal or fizzle, as the noise is electrical as well as acoustic and would get onto the audio. So if it does, it's probably faulty, or being overloaded by a faulty part elsewhere in the mixer.

    Electrolytic caps in SMPS are wear items, but a capacitance meter isn't much use for testing them, you need to know the ESR. (However if the capacitance is way below spec, it's a fair bet that the ESR will be bad too.) The output filter caps are more likely to cause instability than the input ones.

    Random crashes sure sounds like a bad power supply. You can check with a meter to see if the rails sag to weird voltages when the problem appears. This is a sure sign of a problem, but it doesn't tell you whether the fault is in the PSU, or just some part of the mixer overloading it. For that you also need to measure the current.

    The secret of complex repairs is to keep dividing the system in half and testing which half the bug is in. Complicated systems should be designed as a bunch of modules to allow for this. In this case, we want to find if the fault is in the PSU, or the "rest of the mixer".

    This doesn't catch "systems" faults, where the system doesn't work even though the modules all test OK. The fault is in the interaction between them. An example would be if Behringer accidentally made the power supply too small to meet the worst-case demand.
    Last edited by Steve Conner; 04-07-2011 at 10:15 AM.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    Junior Member fznuk's Avatar
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    Well, i hear what you guys are saying and appreciate your help and advice. I really thought the changing of the output caps would cure it like with a few other SMPS power supplies on other items i looked at, but i suppose it all depends on why they failed.

    Im not new to electronics but i am quite a bit rusty since im not repairing electrical items every day, and usually its simple repairs...and can vary depending on the job. My main job now is PC repair which never really requires any component level repair unless im just doing basic diagnosis rule out a bad motherboard....and then its just thrown away and replaced. Google is my friend at the moment for any literature in brushing up on some refresher basic electrical repair knowledge....im just too lazy sometimes to do a full read into deep specific repair....im more of a practical than a theorist...if you get what i mean

    I would like you at least try to repair this desk as i dont like to give up to easily...and still have a hunch that it may be a PSU problem....but as said, it could be a bad component on one of the other boards thats bringing down the PSU?

    a Couple of things before i dive right in again...

    1) The PSU audible noise, could this be bad coil design / transformer vibration and part cured by resin?

    2) Is the noise due to instabilities with the PFC control to the switchers?

    3) The noise was there when the PSU was powered up without the desk connected so does this point more to the PSU than a problem on the other boards or could the damage still have been done by another board fault so now the PSU components have been weakened in some way?

    3) I only tested the analogue power output rails so will test all next time. Is there an accepted tolerance with the voltages before being too high or too low?

    I think a more thorough test on the PSU is needed or do you still think im out of my depth? Please remember i have nothing to loose going deeper since the desk is faulty now anyway? But i still dont want to go round in circles.....and im enjoying learning more on SMPS PSU's

    Thanks again guys...and thanks for helping a novice comparison to yourselves always great to learn from experts - this is why apprenticeships should make a come back!

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    Quote Originally Posted by jrfrond View Post
    In an effort to help here, I just checked every DDX3216 repair in our database. Overwhelmingly, the solution we took to the problem described here was the replacement of crystal Q3, 32.768kHz. Over and over, the problem reads the same: runs for awhile, then locks up, no control, etc. Sure, there are also the ubiquitous cap issues and poor soldering, but this fits the bill. Hey, it's worth a shot. You need to eliminate this common issue first. We stock these crystals. Mouser has them as well, part# 559-NC38-LF.
    THAAAAANK YOOOOU John R. Frondelli!!!! You made my day! I read this, and found this crystal on an old, oblolete PC-motherboard I had, so I took that and replaced it on my DDX-board, and...... TADAAAA!!! It worked again!!
    I have repaired the PSU, fixed bad connectors, but the problems always came back. The last time, it did not start at all! I have to make a "long-time-test" now, but I'm very positive!
    Once again, thanks for your information!


    /Nisse

  23. #23
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    Quote Originally Posted by Nisse View Post
    THAAAAANK YOOOOU John R. Frondelli!!!! You made my day! I read this, and found this crystal on an old, oblolete PC-motherboard I had, so I took that and replaced it on my DDX-board, and...... TADAAAA!!! It worked again!!
    I have repaired the PSU, fixed bad connectors, but the problems always came back. The last time, it did not start at all! I have to make a "long-time-test" now, but I'm very positive!
    Once again, thanks for your information!


    /Nisse
    My pleasure. That's what we are here for.
    John R. Frondelli
    dBm Pro Audio Services, New York, NY

    "Mediocre is the new 'Good' "

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    No power on ANAOUT on ddx3216 PSU

    Hi again,
    Now, when there is an expert available , I have another question/issue on my ddx PSU.
    The thing is:
    I power up the DDX, let it be on for a while (more than 15 min. so it gets warm). Everything is working fine.
    The I turn off and then on. Now it's very likely that there is no power on the ANAIN02. (Sorry, wrong in the title) (It's the +-17V and +5V anaolg power)
    If I then turn off, wait for a while, and the turn on, it might work again.
    I have replaced all the electrolytic capacitor (except the two big ones on the high-voltage side)
    Do you (or any one) know about this, and what component(s) I must replace?

    Best regards,
    Nisse
    Last edited by Nisse; 05-12-2011 at 07:25 PM.

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    I'm new to this forum, and am currently having problems with my desk. I have taken it apart and it seems that it has the usual capacitor problems with the PSU, but I can't get any voltage out of any of the rails at all as they all seem to be shorting to ground. My Dad was an electronics engineer and typically I didn't ask him enough questions before he died, so I'm wishing he was alive right now. If there are any friendly electronics engineers near Aylesbury, Buckinghamshire, UK who wouldn't mind helping me out, please let me know.

    Anyway, I am going through the process of trying to fix it currently using my Dad's test gear, and I came across this forum. I have uploaded the complete schematics for the DDX3216 (including the PSU) as a zip file onto the following url for anyone to download if they wish - the file may only be available for a limited time though so if it ain't there, just email me and I will upload it again;

    http://www.sendspace.com/file/if20vu


    Cheers
    gassanov likes this.

  26. #26
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    Fantastic!! Where/how did you get the schematics? I've searched a lot on the net for this, but never found anything! Thanks a lot!
    Well, as mention earlier, it's quite usual that there are bad solderings on the PSU board. The first step would be to check them. It's very hard to see if the soldering is bad just with your eyes. You will need at least a good magnifying glass, or microscope.
    Here's an image of a typical bad soldering that I had on my PSU.
    (Click on it to enlarge)
    /Nisse
    bad_sold.jpg

  27. #27
    Junior Member fznuk's Avatar
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    Fantastic x 2! Thanks for the schematics!!

    Still had no joy in fixing the original problem but now got the power supply on my test bench within my workshop so i just need to put some time aside to look at the schematics, test the voltages & stability, then have a look into why a ceramic disk is 'hissing'?!

    The Cap (C4 on the Schematic, 223 1KV) starts to hiss/high frequency vibration?! after about 30 seconds of the PSU being switched on (without load or connection to the desk). - this part of the circuit also shares a Transient Voltage Diode and large 18K resistor across it.

    This Circuit is repeated twice again on the other two switch mode circuits (I see this PSU as having three seperate SMPS PSUs in one)

    I did notice the voltage across the resistor varying 79 - 85V while the other two similar circuits were stable if thats anything to worry about?

    Will reply again once i have tested all output voltages.

    Cheers again all! - your all stars!

  28. #28
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    Doesn't the "PSU & DUMMY LOAD" document suggest that the PSU cannot be switched without a (quite complex) dummy load? I think that the noise that you get is due to the fact that you don't have a dummy load. There must be a reson why they provided the schematic of such a complex dummy load, don't you think?

    Mark

  29. #29
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    Replaced all electrolytics and ceramics in the 17 volt section

    Just replaced all electrolytics and ceramics (and CX and CY caps) in the 17 volt section and all the electrlytics throughout the rest of the board (I used 125 degree ones wherever available).

    Before this, all of the signal clip lights on the desk lit up and that was it. My problem now is that all of the lights on the desk are lighting up alternately. All of the meters, every alternate mutes and select button, every other button and every rotary encoder and all of the fader motors are on and under tension - after doing research, this seems to be a typical problem.

    Whilst this is extremely pretty, the desk is still not working. My research tells me that this is due to fluctuating voltages on some of the rails when under load (possibly the 12 volt rails to the CPU board). I'm now testing to see what is causing the problem. My C4 cap is also hissing. Speaking to several repairers about the board (which it turns out behringer nicked from a plasma TV) the zener diodes (zd1 - zd4) are common failiures, followed by some of the rectifiers and regulators on the board (U3 and U4, KB1M0880). Also, CX1, 2 & 3 and CY caps are also prone to failiure causing shorting to ground and overheating of the in line CX variety.

    I may go through the whole board and replace more or less everything (excluding the trannies) as I reckon I could do this for around 100, which seems pretty cheap. Most of the components are readily avaiable or modern better performing equivalents are readily avaiable.

    Something I did notice when replacing the ceramics, several of the 104 ceramics on the 17volt rail were actually 103 caps instead. If I replace them with 104 caps as it says in the schematic, will this have any adverse effect?

    Also, J7 (AG - DG) isn't present and the screw connecting the heatsink to the board accross the AG and DG rail isn't present? Is this normal? I can't see how it would affect the board and I assume you would want to keep DG and AG separate wherever possible.

    Watch this space

    Glad my schematics are of use to people.

  30. #30
    Senior Member Enzo's Avatar
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    Generally on any mixer or similar piece, when I see all the peak lights on, it usually means one of the power rails is missing. So check the +/-15VDC to the analog ICs.
    Education is what you're left with after you have forgotten what you have learned.

  31. #31
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    Quote Originally Posted by gonzosaxman View Post
    ........Also, J7 (AG - DG) isn't present and the screw connecting the heatsink to the board accross the AG and DG rail isn't present? Is this normal? I can't see how it would affect the board and I assume you would want to keep DG and AG separate wherever possible.

    Watch this space

    Glad my schematics are of use to people.
    Hi,
    Just what I noticed!!
    I have two PSUs.
    One older and one "newer" (green and blue board)
    On the older, the screw is missing, the jumper J7 is not mounted and the AG is disconnected from DG, but on the newer (which fails on analog power, described above) has the screw mounted, jumper J7 mounted, and the AG is connected to DG! I started to wonder if this could have something to do with my reboot problems... What's right?? Should the AG and DG be connected in the PSU or not?

    Regards
    Nisse
    Last edited by Nisse; 06-28-2011 at 06:54 PM.

  32. #32
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    Please Reupload DDX3216 schema...i realy2 need it!


    thx

  33. #33
    Supporting Member Jazz P Bass's Avatar
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  34. #34
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    And now, finally, I've managed to repair my PSU to work 100%.
    The problem is described in "No power on ANAOUT on ddx3216 PSU" above.
    As mention above, it's not just the electrolytics that is bad. Beside some bad solderings, the flat cheramic capacitors is a disaster.
    For me, it was the C52 that was the problem, and here is my analys of the situation:
    The PC3 works as a voltage regulator to Q3. It gives feedback from the lo-voltage-side to the transformer driver (Q3) on the high-voltage-side.
    As mention above, the PSU worked fine (without failure as long as it was on), but when I rebooted it when it was warm, there where no power on the analog outputs. As I can see in the schematics, the C52 works as a "soft power up regulation" to Q3. If the C52 wasn't there, the PC3 would tell the Q3 to go by 100% at startup, because there is no power out yet. This will perform until the right level is achived on the 17V side. This would probably work if the Q3 hadn't have a over-current and over-voltage protection. So that's why we need the C52, to make a more soft startup, while all electrolytics etc. are charged. Now, when I examine my C52, it has a value of 110 nF at 20 C. It's Ok (Should be 100 nF +- 10 or 20%). But when I just warm it up a bit (with my fingers) to about 30-35 C, the value goes down to 75 nF! If I then warm it up to a temerature that I just can hold my fingers to it without burning my self, the value goes down to 40 nF!! So now, the "soft startup" is not enough, so the over-current feature in Q3 is activated, and power the Q3 down. That's why it never will start up as long the power is on, even if I wait for temperature to go down. I need to restart when the temerature is low. This is also the reason why it is working as long as it is on.
    So now, to be sure that this won't happen to more places in the PSU, I will replace all the cheramic flat capasitors to multilayer 125 C. capacitors.
    One other thing that is really strange is that the elecrolytic capacitors are "high temp 105 C" while the cheramics are not, or am I wrong here?!
    Anyway, in my project to repair the PSU, I've also mounted a fan on it, to extend the lifetime on the PSU and the DDX. If any one is interested in that, I will publish some pictures of it, and describe how to do and how it works.

    Regards,
    Nisse
    Last edited by Nisse; 07-05-2011 at 09:48 AM.
    zeubest likes this.

  35. #35
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    thankyou sooooo much!!

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