Behringer DDX3216 - Trying to repair, please help!

[Han]

I know it's 2017 and your post is since 2012 but if you have that DDX Update software I need that too. I have same message "No valid program...". I hope you still have it.

Hello, i attached the files

[sazema]

Hi,
So how do you replace your capacitors if you don't dismount your PSU?
By the way, I think you have to clean your PSU-fan a bit!

Well, does anybody know the difference between the V112.bex and V109.bex? For me it looks like V112.bex is a newer firmware, but on behringes homepage it says:
V109.bex = Latest firmware
V112.bex = Audio software (surround software)

Do I need to install them both?
How can I see the installed version(s)

Ps.
If anyone needs the DDXUpdate, I can share it for you.

/Nisse

I know it's 2017 and your post is since 2012 but if you have that DDX Update software I need that too. I have same message "No valid program...". I hope you still have it.

[dutch_anykey]

Left it runnning for a few hours, and still going strong.
clear display, no heat sensitive symptoms.
I'm happy that it works now. But it is still bothering me that I don't know the real cause. The right thing to do would be soldering back the caps and start measuring like Nickb suggested. Start with checking what is going back into the negative inputs of the lm324. Maybe there the problem starts. Also the design of this voltage follower can be different I think. Why all the capacitors in series. Since the voltage coming out of the opamp output is regulated, the caps could be terminated to V- I think.
From the other hand...it works. And I don't want to go over cleaning the LCD again and risk loosing traces on the pcb. I'll save it till the time it brakes down again...and if it is still interesting to fix a ddx3216

Maurice

[dutch_anykey]

Hi Nick,

Good advice regarding the 10 ohms resistor for measurements.
Also I followed up on the cap removal. It was getting messy. But I did a few things...
Firstly I got the LM324M and the panasonic 4,7uF caps in the mail. So I replaced it with the LM324...result garbled display. But....I have to admit that I caused that myself. When desoldering the old LM324, I used some flux. Apparently this flux went through the holes on the pcb (the through hole connection that connect to another trace on the other side of the board) So when opening the LCD assembly again I found flux between the elastomeric connector and the glass plate....pfffffff.
Cleaned everything with alcohol again and put it together....garbled screen again...
Ditched the 4,7 uF caps. same result. desoldered the lm324M and put back the older lm324...pronto...good screen.
I suspect I killed the lm324m when the flux was on the connector....but i'm not sure. Like I said, it is getting messy. Also the traces on the pcb are starting to get bad because of all the heat from soldering.

But at this moment it is working with a lm324 and no caps. I leave it like this for a while. Probably build the screen back into the mixer and leave it on for a day and see what happens.

I don't know about you...but at this moment I need some kind of success in my repairs...sometimes repairs go well, and sometimes nothing works...I find myself in the bad stage at this moment haha.

br
Maurice

[nickb]

If possible, I would add a small resistor say 10 ohms between the LM324 and the driver chips. By looking at voltage drop over it using two scope probes in differential mode, you will be able to see if that is where the current is going. I would expect the LM324 to feel hot too if so much current is being drawn that it fails.

The caps should not be that temperature sensitive - that is very odd. I'd be tempted to remove the caps that attach to that output. The output impedance of the LM324's is very small up to 100KHz+ therefore I think you could remove the two caps that attach to the troublesome output just to see what happens. I wonder if that section might be oscillating.

I am not aware of any major differences between LM324 but I suppose one manufacturer will differ from the next.

[dutch_anykey]

Hi,

Short update.
Measured everything again. inputs/outputs of the toshiba T6A39's en T6A40. Can't find anything wrong. Again, disassembled the display and put it together again. Soldered a new LM234. For now it is working again, but still very sensitive to temperature changes on the 4,7 uF caps.

I ordered the LM324, didnt look any furhter on the details of this chip. But I checked the original one that I took of the first time. And it is a LM324M. Not sure if this would make a big difference, I checked some data sheets. And at least from the few doc's that I looked in, I can see that the LM324 actually can manage a bigger output current than the lm324M.So that would be a plus or the lm324. But I read from the LM324M specs that it has an internal temperature adjusting circuit, can't find that on the lm324 specs. Anyway I ordered the LM324M and will test it, also ordered new Panasonic 4,7 uF caps. Maybe the panasonic's are better then the "Würth Elektronik" ones I have now.
Anyone can confirm differences in behaviour from the lm234 and lm324M?

Maurice

[nickb]

Thx for the link. That's commonly called an Octopus or sometimes 'component curve tracer' (very misleading name) - current on Y axis and Voltage on X. Dirty cheap component tester (a.k.a. ?Octopus? curve tracer) ? JAMMArcade.net It allows you see see the phase relationship between V & I easily.

[dutch_anykey]

Hi,

Regarding the tracker (anyway that's how we call it locally here) I did a quick search on youtube https://www.youtube.com/watch?v=BF0cdoetwRw , so it is more or less the first vid I came across that shows the working. It's not the device/brand that I have here. But it pretty much shows what it does.

Before I go measure again I want to check also another thing that came up in my mind. I disassembled the lcd and put it back together as I told you. As for alignment of the display, the contacts in the elastomeric connector are very close to each other. so the contact distances on the PCB and LCD are far bigger. Can't go wrong with making and unwanted cross connect was my idea. But I forgot that the PCB and the LCD itself should of course also be aligned properly to each other. I have to check if it can be miss aligned. But it's one thing to check before going measuring again.
And indeed these "V" voltages are fed to toshiba display drivers (three T6A39 column drivers and one T6A40 row driver). They are responsible for the multiplexing of these voltages to the right columns and rows. Now I have to find out if one of these chips is problematic or the LCD itself.

[nickb]

The problem with messed up multiplex voltages on an LCD is that if on average there is a DC voltage then it can damage the LCD. It is possible you could isolated the 'bad' LM324 output from the driven part ( cut track) to confirm that the driven part is the problem? I would expect these voltages to do to a switch of some kind that actually does the multiplexing. If that is external to the LCD then you may be able to replace it. If internal, then game over.

I have heard of many kinds test equipment in this area but a component tracker is a new one on me. I suspect something might have been lost in translation. Perhaps you are mean a Bode analyzer (Vector network analyzer)?

[dutch_anykey]

Hi Nickb,

The display is all garbled again (so it got worse)
The capacitors are new and just double checked that the orientation is right. I quickly measured with a component tracker (not sure if you know this device in combination with a scope) from there I can see that the output of the lm324 is most probably dead again. It is late so I will measure decently tomorrow.
What I have observed on the LCD glass plate itself in this faulty mode is that there are some darker lines. And I mean darker so that they stand out from other black lines. Maybe this indicates a short in the lcd itself, So it gets a combination of voltages on those lines and therefore are more black. Perhaps that's why I was seeing this abnormal voltage on the lm324. So that voltage not coming from the lm324 side, but coming back from the lcd plate.
If the LCD plate is shot, I'm done. No way I can find a replacement. But I will try to measure and find ways to confirm that tomorrow.

As for the mixer itself, during the time it worked I took the opportunity to fiddle around with it. I must say it is very nice with the compressors. limiters, FX's and more stuff build in. So the basic things really can be programmed without knowing to much about this unit. And it saves the need to have external effects and compressor/limiters.

[nickb]

Is there any chance C7 (on your schematic) is bad or inserted the wrong way round on the board?

Those voltages should not be so sensitive to temperature. The capacitor leakage current might vary a bit with temperature but the output impedance of the LM324 is so low that it should not matter. Quite possibly, with one output bad, that voltage is varying as the LM324 is not behaving as it should.

[dutch_anykey]

One more thing,

Maybe people that own a ddx3216 can help me on this one: Do you have to play a lot with the contrast pot during normal use?
I build the display in the case and put the few hundred screws back in to have it completely finished. But I experience a rather high temperature drift that needs constant corrections on the contrast pot.
So, took the display out again, and then noticed when holding my fingers on the 4,7 uF caps that the contrast changes. blowing cold air over it changes it in the other direction. One of the first things during this repair was changing the caps for new ones because the old ones measured zip capacitance. I wondered if the new caps might be wrong.... It's the standard alu smd caps. So I changed them for normal electrolyte caps. But the result is more or less the same. I wonder if there are caps that have solid capacitance over a wide temperature range.

br
Maurice

[dutch_anykey]

Hi g1,

Yes the the voltages on the input resistors are stable. It's really the output voltage that is slowly slipping. BUT, i got a little further and I think I found the reason for this
I also told you that I disassembled the LCD and that I was missing some lines. So I took it apart again cleaned everything with 99% alcohol and carefully put it together again. And surprise the display is working o.k. now. Maybe in one corner it is still a tad off. So nickb was right on the money here with the comment about the elastomeric connector!!

From what I see now, this might have be the root cause of the display not working when I bought it and killing the LM324. What might have happened is that some connections got shorted through this elastomeric connector and a higher voltage was fed back to to lower voltage connection. The guy where i bought it from was using it "in the field" So I bet this unit has had it's fair share of beating and bumping when moving it around to and from gigs. I guess the elastomeric connector got shifted.

For now I'm afraid that this unit can only be used in a stationary studio environment. Not really a situation that I bought it for. But lets see how it goes.

So thank you all for thinking along with me! It was a great help. Next on the table will be a behringer EP2500 PA .... I already took a peek. I thought it would be simpeler then this mixer, but I noticed this 2 step power supply in the end stages...brrrrr

Here is the drawing i made up to understand what was going on:

[g1]

there is a series network of resistors R5,R4,R3,R6 and R2. So they work as a voltage devider. There you have the voltages, but you can not bring this voltages directly to the display since it will alter the voltage when a load is added to the resister. Her the LM324 comes in. It is wired to be a "voltage follower" it means it reproduces the input voltage and outputs it on the output. In this way it can handle the load request from the toshiba drivers.

What I found on my display is that one voltage was way off on the output of the lm324. Ordered a new one and put it in. Voila it works...happy dance. But only for 5 minutes. Because the display was turning darker and darker again. So I suspect the new LM324 is dying again. weeeeh.

Those resistors and their solder connections are good? Can you verify that the voltages going in to the lm324 are remaining good while the outputs go bad?

[dutch_anykey]

Hi guys,

Some good news and some bad news.
So I did proper measurements on the LM324 circuit. The circuit is responsible for producing the various voltages need to drive the lcd. (v2,v3,v4,v5 and vee) it goes to the toshiba row and column drivers. the total sum of this voltage is this negative voltage that comes from the SCI7654 chip and this voltage is also altered by the contrast pot. (varies between -9.36 and 12.3 volts in my case)
To get the separate voltages v2.v3 etc. there is a series network of resistors R5,R4,R3,R6 and R2. So they work as a voltage devider. There you have the voltages, but you can not bring this voltages directly to the display since it will alter the voltage when a load is added to the resister. Her the LM324 comes in. It is wired to be a "voltage follower" it means it reproduces the input voltage and outputs it on the output. In this way it can handle the load request from the toshiba drivers.

What I found on my display is that one voltage was way off on the output of the lm324. Ordered a new one and put it in. Voila it works...happy dance. But only for 5 minutes. Because the display was turning darker and darker again. So I suspect the new LM324 is dying again. weeeeh.
I will go on for a little bit. But this thing is just about to get me down and give up. I suspect the the toshiba driver is going faulty and drains to much power, or the lcd itself is faulty. Not sure how i'm going to check this yet.

Another thing that i haven't mentioned yet, just before i found the lm324 fault I also decided to disassemble the LCD itself and check these rubbery connection...So I'm missing a few lines But I guess I can get those back with adjusting the alignment of the rubber.

I will put up my drawing this evening of the circuitry of the LCD that i have drawn up. Maybe some future reader can have an advantage of it.

br
Maurice