[SteinarK]

As several others in this forum, I got issues with the amplifier in my M2 Competition (build date of amplifier 08/19). Lots of extremely loud popping and crackling noise from the speaker system. Especially when hot.

I realize a lot of M2 owners have got their amplifier replaced under warranty, where also a splash shield/guard is installed with the new amplifier (https://static.nhtsa.gov/odi/tsbs/20...61573-9999.pdf).

Since my car is out of warranty, I decided to open up the amplifier to have a look.

I could clearly see that there had been some moisture issues (watermarks) on the outside of the amplifier.

After opening up the amplifier, I was a bit surprised to see the amount of thermal paste used on the power electronics. Thermal paste was clearly hanging outside the power components, not far from the pins on the power electronic chips. Seems also like a bug had tried to find shelter, since the leftover of the bug was still present, sticked to the paste

On one of the power electronic chips I could also see some moisture/droplets still present (can see it on the picture below). Further there were clear signs of copper corrosion on the pins as well as black burnt carbon deposit.




I cleaned the power electronics (HBCD412A), and re-installed the amp in the car. To my surprise the amplifier worked as it should. Need to do some further investigation, before I conclude...

If the power electronics chip (HBCD412A) is bricked, a new one cost ~6 USD.

[SteinarK]

Part 2:
Mounted the bare PCB in the car, and heated component by component to ~65 deg C, in an attempt to provoke failure. Especially the cleaned power circuits had my attention.

I was not able to provoke failures. No issues at all. The next days will show if the "fix" was sufficient or not...

A splash guard (part number 65 15 2 715 205) and a couple of HBCD412A are ordered, just in case.

If the "fix" shows sufficient, I will add new thermal paste and cover the pins on the components with silicone coating for electronics.

My hypothesis: The splash guard will only protect the amplifier from direct water intrusion, but not condensation. It is likely that water will still be present in the environment where the amplifier is located. When the sun heats up the car, the water will evaporate, causing humid air. When the amplifier is used, a lot of heat is generated in HBCD412A and transferred to the surrounding via the large cooling lid. When the car is parked, and the amplifier is shut off, the moist in the air condensates as droplets (due to cooling) on the cooling lid just above the HBCD412A. If the car is used for short trips, it could be that droplets (or a small water film) are built up, large enough to create corrosion, conduct current and cause short circuiting between the pins.

[SteinarK]

Part 3:
After several days with no issues, I assume (or at least hope) that the amplifier is fixed/cured.
Opened up the amplifier again and coated the pins on the HBCD412A circuits and the nearby area with silicone coating for electronics (422C from MG Chemicals) as well as applied new thermal paste on the HBCD412A and on one of the voltage controllers (indicated on the picture by red circles).




Awaiting the splash guard as well as a Pingi Moisture absorber that will be installed at arrival.


Some side notes:
1: Thermal paste: The expected lifetime of a high quality thermal paste is 2-5 years! Is the change of the thermal paste a part of the BMW service schedule?

2: The last incident with popping and crackling noise from the speaker system, was so loud that it hurts. Since at least one hand is required on the steering wheel, I was not able to protect my ears with my hands. The sound/noise was picked up by my Apple watch. Under a layer of a fleece jacket and a down jacket, it recorded ~105dB for ~4 minutes. I would claim that this is represent a traffic risk/hazard, especially since one are not able to shut off the amplifier. The only options is to stop the car and pull the fuse.



3: To me it seems like if one pull the amplifier fuse right after the first incidents of popping and crackling noise, one might be able to save the amplifier by opening it up, clean it, apply some coating and re-apply thermal paste (and install splash guard).

4: It might also be beneficial to install a moisture absorber, in order to suck the moisture out of the air, as well as absorb water entering the amplifier surrounding. Need to gather some experience ...

[chris719]

You may want to look at the ASD module as well if you haven't already bypassed it or looked inside it. That could probably fail in a similar way and give you nasty transients on the outputs.

[SteinarK]

Part 4:

After a long waiting time, the splash guard did finally arrive. Installed it together with a moisture absorbing pad.

Opened up the ASD as well. No signs of moisture issues in it.

For the record: The amplifier still works without any issues :-)

[chris719]

Originally Posted by SteinarK

Part 4:

After a long waiting time, the splash guard did finally arrive. Installed it together with a moisture absorbing pad.

Opened up the ASD as well. No signs of moisture issues in it.

For the record: The amplifier still works without any issues :-)

Good to know. Really appreciate you taking this apart to check. BTW what do you think the chip marked H is? I can’t read the letters that clearly, almost looks like an Analog Devices part number but doesn’t look like one. The other chip is a Renesas / NEC MCU. That must be some kind of audio codec or DSP I’m thinking. The whole ASD module is strange and wasteful. It would be super easy to mix the fake sound digitally in the head unit.

[DriftKr6l]

Nice write up

[SteinarK]

Originally Posted by chris719

Good to know. Really appreciate you taking this apart to check. BTW what do you think the chip marked H is? I can’t read the letters that clearly, almost looks like an Analog Devices part number but doesn’t look like one. The other chip is a Renesas / NEC MCU. That must be some kind of audio codec or DSP I’m thinking. The whole ASD module is strange and wasteful. It would be super easy to mix the fake sound digitally in the head unit.

The "H"-chip on the ASD: The same chip is on the amplifier as well (lower right corner). ADW80008YSTZ seems to be an Analog Device DSP-processor