QSC TouchMix 16 sound problem fixed (other touchmix versions may also get this)

Hi, I have a TM16 that is SN: LLE0G1192, which I believe indicates it was manufactured in Dec 2014. I bought it used about a year ago and soon discovered Aux 3 had little to no output, so I simply didn't use that output when gigging. I finally decided to tackle the Aux 3 issue and discovered this thread. I'm glad I did!! The info here has been invaluable to me. I opened my TM16 up and found not only a bad cap (bulging) on Aux 3's output, but bulging caps on both the left and right Mains (all 4 caps). The Mains have been working ok as far as I know but I'm pretty sure it was just a matter of time before I would have had a failure and most likely at a gig! Anyway, I have new caps on order, and I've removed all the output caps for the Mains and Auxes 1 thru 6, while I wait for the new caps to come in. I have pics to post of the bad caps and PCB where they were removed from, plus pics of the display ribbon cables and Master Controller connector J1401. Disconnecting J1401 was not easy as it's been connected for 9+ years. I'm thinking that the plastic on the connector and surface mounted socket it goes into have been baked by the above average heat that the TM16 generates and they more or less fused together. I worked them apart little by little using two jeweler's screwdrivers (one on each side of the connector) and luckily nothing broke. Pulling on the wires like I saw in a You Tube video was not an option to me because the wires would not take the strain of the pulling given how tightly fused together the connector and socket had become. Anyway, that's it for now. Once I get the new caps installed, the unit put back together, fired up and checked out, I will return to post the outcome of my repair endeavor.
 

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Hey Paul,

The backwards capacitor problem affects both the TM8 and TM16 with the following main circuit board part numbers:

PC-610203-00 (TouchMix-8) or PC-610303-00 (TouchMix-16)

So if you have a main circuit board with these part numbers, you need to remove and either replace or reinstall the old capacitors but in the opposite direction of what is shown on the circuit board.

Hope that helps.

Cheers,
Brian
Hello Brian, apparently like many others I have low output problems, probably caused by the caps of the QSC Touchmix 16. In your message you indicate that mainboards with the number PC 610303-00 should have the poles reversed. My mainboard shows PC 610303 REV C. Would this board be OK, so replace the caps as they are now on the board?
Thank you in advance for your answer and kind regards
Hans Hulsenboom
 

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H, all I just found my old post von exactly one year ago.At the I got a qualified contact via the German headquarter of course see here and I sent a mixer to the European self-center in the Netherlands. Costs me around 150 Euros to fix the problem incl.delivery.
More less one year after the last problem I have the next mega issue with the TM 16. After a sudden power loss the touch display did not react anymore.
God bless that I have control with a tablet to the mixer. What a poor design. To send the mixer in Standby you can press the hardware Button but you have to confirm with the Touch Display. This makes absolutely no sense.
All this is happened before a gig. In 2 days I have the next next gig and I need a mixer. I have enough now. I think I will again fix the mixer via a service center and then try to sell it.
I'm playing music over 30 years now. I clearly have to say that this is the worst piece of gear I've ever had. It would be perfect if it would constantly work. But you can not trust this peace of gear. I'm totally disappointed.
 
H, all I just found my old post von exactly one year ago.At the I got a qualified contact via the German headquarter of course see here and I sent a mixer to the European self-center in the Netherlands. Costs me around 150 Euros to fix the problem incl.delivery.
More less one year after the last problem I have the next mega issue with the TM 16. After a sudden power loss the touch display did not react anymore.
God bless that I have control with a tablet to the mixer. What a poor design. To send the mixer in Standby you can press the hardware Button but you have to confirm with the Touch Display. This makes absolutely no sense.
All this is happened before a gig. In 2 days I have the next next gig and I need a mixer. I have enough now. I think I will again fix the mixer via a service center and then try to sell it.
I'm playing music over 30 years now. I clearly have to say that this is the worst piece of gear I've ever had. It would be perfect if it would constantly work. But you can not trust this peace of gear. I'm totally disappointed.
Pop the back off and see if the ribbon cable came unplugged. We had that happen on a few touchmix 8 units and it was a really easy fix.
 
Disclaimer: I probably qualify for "caveman" (as defined in #27).

My TM16 was randomly rebooting (started during a live session with 250+ audience... ouch!). I figured I would "reflow" the power connector soldering points. After doing so I could not get connector j1402 back again... Threading it through the slot was hardly possible. In fact I didn't have to disconnect it in the first place, I just did so in order to "have a closer look". Searching for a video on someone reassembling a TM16 I stumbled upon this thread...

Then reading post #10 I realized that I didn't have to go to all this trouble in the first place! It's that 6-pin connector!

While "reflowing" the power connector I did see some boiling and even splatter of flux trapped inside so maybe it wasn't completely useless.

However the reason I'm reacting here is my great surprise and disappointment... I always had the impression that this mixer had balanced outputs, and that balanced outputs would by nature eliminate problems with unintended phantom power due to a built-in transformer (similar to a ground-loop filter)... So either the TM16 does not have balanced outputs or my perception on balanced out/in is wrong... Could someone enlighten me?
 
...

However the reason I'm reacting here is my great surprise and disappointment... I always had the impression that this mixer had balanced outputs, and that balanced outputs would by nature eliminate problems with unintended phantom power due to a built-in transformer (similar to a ground-loop filter)... So either the TM16 does not have balanced outputs or my perception on balanced out/in is wrong... Could someone enlighten me?
A differential drive pair of opamps does not a transformer make.
 
Hello Guys
I will kindly ask you for help with the Main Out Smd Transistors. The Singnal has asymetric amount. So i searched the problem at the Kondensators. They are working good. ESR is in good way. The SMD Transistors Label is 'WM5 B' and he is shortened. What kind of Type should i try to exchange the damaged ? This is very less Information. If there anyone knows a good Database, let me know.
 

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I fixed a problem likely heat related, as these things run a bit hot.
I hope this post helps people having a similar problem as boards are all just replacement these days, and that's pretty much the whole unit.
Note: Read the 2 addendums below from Brian.

I got one of our touchmix-16 units in the other day and had to fix a low and missing some sound frequency on the right channel, I tried resetting everything just to start from scratch, but it didn't help. swapping channels(in and out) it followed it just on output. It didn't seem to appear on headphones. For some reason it was effected by the L,C,R adjustment even though I didn't expect that, but I don't have the schematics/block diagram to see how it effects it. These things do run a little hot with no fan and not much ventilation. I took the unit apart and most of the capacitors at the back of the unit along the AUX inputs and main outputs were slightly mushroomed on top (47uf/63v). Usually in electronics it's the caps in the power supply that do that, but this seemed to just be signal. 6 mushroomed of the 10 caps in the area were reading around 16uf, so I replaced all 10. It totally fixed the problem. I didn't test the Aux before taking it apart, but I'm sure they were effected as well.
I put the same temperature rating in from my stock, but probably best to find higher temp rating to help prevent it, or at least make it last longer.
I don't have the schematic to see exactly what all of the capacitors did, but I think most were just signal related.
If you're handy you could probably add a tiny fan off the supply in since those fans are such low power drain.
Normally our units aren't used every day, but I think this one was in a studio we had built(gone now) and was running
for probably a year and a half straight but only used maybe 1 or 2 days a week. For some reason some techs don't feel the need to shut thing off when not used every day.
Hi,

I think you should did a great job diagnosing and fixing the issue with your TouchMix-16 unit. Replacing the mushroomed capacitors likely addressed the frequency problem you were experiencing. Given that the unit runs hot, adding a small fan could indeed help prolong its life and maintain consistent performance. It is unfortunate that some techs neglect to turn off equipment, especially when it can lead to issues like this. Keeping an eye on ventilation and temperature can make a significant difference in the longevity of your gear.

Thanks