This article is useful for owners of Presonus StudioLive first series (for example, 16.0.2), as new series most likely don’t have a problem described below. Sorry for bad English — this is hybrid translation (by Me and Google).

Prehistory

So, let’s start with how I discovered the problem. The purchased «second hand» digital mixer Presonus StudioLive 16.0.2 was in excellent technical and cosmetic condition.

One day there was a rehearsal of my children’s vocal group. Suddenly, sound disappeared on the microphone and line inputs. I switched the cable into randomly selected channels — none of them worked.

Reboot or reset did not solve problem. It looked like the problem was in hardware. Turned it off and left for a day. Next day the mixer worked fine.

One day the workers installed a fire alarm in the club where I worked. The puncher caused a short-time voltage drop across the network. For some milliseconds, I suppose, electricity was lost. The mixer stopped working again. DSP and all controls seemed to be fine. There was simply no sound at the input, also there was no indication of the input channels.

I established the following:

  • Failure occurs when the mixer is temporarily disconnected from the network. It stops working if you simply turn it off and then on.
  • Specifically on my mixer this issue related to channels 1-12. Only 13-16 worked fine.
  • Disconnecting the mixer from the network for somewhere 20 minutes solved problem.

Searching the Solution

So, it was clear for me that the problem is 100% hardware. I started looking for solutions on forums. I was surprised, but many owners of the first digital mixers Presonus encountered a similar problem.

Unfortunately, in most cases, in people did not want to look for a way to fix the problem on their own and reported about successful repair by service center. If the warranty was expired, the repair cost minimum 100 dollars. Nowadays, service centers simply replace the whole circuit instead of finding solution.

Something told me that solution may cost less than a dollar. I already had the experience of repairing condenser microphone Audio-Technica AT4050 with static (or «farting») noise and an old Yamaha synthesizer, where I simply replaced one cheap IC.

Some day the solution was found. Thanks to the user oscarmonsalvo (Presonus Forum’s user) from South America, we have the opportunity to repair the mixer with our own hands for only 50 rubles.

Why Presonus Mixer drops audio inputs?

Let’s move on to the technical part. The above user has discovered some voltage drop on voltage regulator that feeds the ADC (analog-to-digital converters) of 1-12 ch caused by short-time power outage. Only 3 V was measured instead of 5 V. Replacing component would solve our problem.

Repair

Let’s start by disassembling the mixer. First, unscrew a pair of bolts under the plastic wings on the side, as shown in the photo below.

 

Then unscrew all the bolts along the perimeter of the sidewalls. Bolts in the middle of the plate must not be untwisted.

 

Next, unscrew the bolts from the bottom of the mixer’s edge.

 

After that, unscrew the five bolts over the microphone jacks on the rear wall.

 

Remove the knobs from the preamp controls and unscrew the hexagons as in the photo below.

 

Carefully remove the top cover. Take care not to damage a huge number of wires. Turn off those that will disturb you.

In the center there is a power supply PCB. But we are looking for the main board, which is located directly in front of us. Pay attention to the two dpak voltage regulators, located on the left side near the power connector. They are marked «45 500».

 

Measurements showed that the components do not stabilize the voltage at all — about 7 V arrived both on input and output of voltage regulator. Therefore, I believe that I was lucky, because such voltage can break ADCs. Powering mixer off and the on caused the voltage drop at the first regulator (in the photo it is to the left) — 1.5 V. The second continued to feed 7 V input voltage to ADC 13-16. There is no doubt — we need to replace both voltage regulators.

I tried to find this components by marking «45 500» but nothing was found. Therefore, there was an idea to replace the regulators with common 5 V 500 mA voltage regulators — L78M05. I replaced these components and finally made my console work fine.

 

I  hope my article was useful. But be very careful — don’t try to replace components if you are not experienced in this.

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