Mazda 3/axela bose audio amplifier repair part 1

In this first part, using no schematic, we hypothesize what's wrong using our brain and datasheets to make an educated decision.
Be sure to check out part 2 here! - • Mazda 3/axela bose aud...
Tools I use -
Soldering
Quick 861DW hot air station
Duratech TS-1640 solder iron
Multimeter
RMM760D - can be found under many name badges
Microscope
Luzky Zoom 3.5 - 90x simul-focus single boom stand trinocular stereo microscope
Camera - Lucky Zoom HD 14MP
Oscilloscopes
Siglent SDS 1102CML 100MHz 2CH
Philips PM 3305 35MHz 2CH
Bench supply
Powertech MP-3086 0-30V 3A
TL866II PLUS universal EEPROM programmer

[@DerbyRepairs]

İ was trying to fix the same amp when i found your video by mistake. Very helpful. Saved me time! Thank you!

[@hal6702]

Thank you for the video. I have an identical board and I tested everything you suggested in Part1 & Part 2 (as well what was mentioned in the comments section), but sadly it still doesn't want to work. All 3 IC amp. warm up in a similar way (I tested using an IR thermometer). The main headunit was replaced by another one of the same model; no improvement.

[@griffo3043]

Top work mate helped me fix my amp exact same symptoms exact same fix. $10 chip.

[@TheDefpom]

Follow that reset line from the debug port, that will likely be coming from a supervisor IC, or possibly even an op amp comparator with an R/C network to provide a turn on delay.

[@JonnyFix]

The processor creates a pulse train which is monitored by the 5v reg and if not present the reg pulses the reset line. Thanks for the idea tho!

[@morejelloplease]

modern CX5's use this. they also implement EHE or engine harmonic enhancer, which takes signals from the engine rpm and transmission gear selector and inject it into the bose for the "fake engine noise" do you know the pin out or which wire to remove to try and disable the fake engine noise on the mazda cx30, cx50, cx5, etc? i'm seeing HS CAN high/low and Pulse width modulation control, i think it's one of those.

[@JonnyFix]

It might be the CAN lines but that carries data that will control many other things so cutting them will cause issues, high/low work together.

[@craigw7471]

Wow, that’s practically the same amp that came out of my 2015 Chevy SS and is used all throughout GM from about 2005-2012

[@DanielVNZ]

disregard last comment, found a replacement same model number :) @Jonny Fix if you want another one of these, let me know and ill ship it to you, current problem is when its plugged in, literally sounds like a machine gun going off

[@DanielVNZ]

Hi! Does anyone know if GAN6 66 920A and BBM4 66 A20 both have the same pinouts? Both units look identical to the one in your video. I took the GAN out of my car but unable to purchase literally anywhere but there seems to be lots of the BBM variant

[@JonnyFix]

Not sure, it's hard to find any information on them. If you can afford to take a punt on a BBM unit e.g. it's easy to re-sell if you don't want it then maybe get one, open both, see if they are built identically, same parts in same layout etc. Even do some checks to see if the pins go to the same places.

[@andycarassi5609]

How do you know if it’s bad

[@CnDrcnsProductions]

Hello, great video, it helped me a lot to debug mine amp! 🎉 I have a couple questions maybe you are able to answer… The first: I have noticed the rear speakers are running less than half volume of the front pair, looking at the pinout of another bose amp with the same connector I have discovered there is a pin (B2) called "rear seat audio enable signal" and I have traced it on my amp pcb and actually it goes into some components! Maybe applying v+ to it will make the volume equal front to back? Second question: I have not the original hu but I know it someway digitally controls the amp’s dsp and output levels (and possibly even update the amp firmware, although badly😅). I have tried to figure out what pin(s) does the magic and A1 to A4 seems plenty to accomodate 2 differential data lines one from the hu and one to the hu. But I am not certain since in all the pinouts I have seen so far are marked N/C. If I am right, do you have any guess on what protocol is used for this "digital connection" ? Thank you a lot❤

[@JonnyFix]

A pinout I found shows the green connector has a red wire and white wire which are on a can bus and a yellow/black stripe and brown/white stripe being serial comms to HU. I think there are a couple of different pinout for physically similar amp module but info is hard to find. You'd have to reverse engineer the protocol. The rear seat enable i would think would be just that not some level of audio. You said it was half the front level, does it change with volume control. Could be a front to rear fader setting more likely. If you don't have the factory HU maybe the amp is stuck on that setting. Good luck!

[@novacartech7588]

Hi mate thanks for sharing your knowledge with us , could u give me the details for ur Oscilloscope ? Thanks

[@JonnyFix]

Siglent SDS 1102CML

[@MrKaaz]

Mate, I have a Bose amplifier out of a Chevrolet vehicle. It doesn't turn on/play sound until it warms up, then works totally fine. I'v tested in the vehicle, I can warm it up with a heat gun and it turns on in less than 30 seconds, every time. I have some basic decent solder skills. Any guesses to what would cause that? Thanks.

[@JonnyFix]

Sounds like a bad solder joint in there. If it's the same as this one, the IC talked about at 11:34 has been known to have bad connections, I think my first video on these things was that. So hook it up like I have and test the voltages around here and prior up to about 14:00.... or if easier take it apart then plug it back into car for power source. If you have a missing voltage when cold I'd start with re-soldering the related reg.

[@AnonymousRepair]

Did you try to read the eeprom ? see if there is any data on it

[@JonnyFix]

Nah I didn't think there was any point as there's no activity on the clock/data pins the processor isn't even trying to read it.

[@benkozs]

Brilliant videos on this cumbersome amp, thanks for sharing! At 13:55 you measured 1.8 V on the LDO which I think is way too high as the DSP's absolute maximum Vcore is 1.6V and in this circuit it is normally run at 1.25V. It seems that's what killed it... Have you measured the voltage again with the new DSP? Hope it didn't die after a while with the 1.8V on it...

[@JonnyFix]

Oh interesting point you have. Maybe that is what it causing the failures. I really don't know, I will have to watch out for that next time I get one. Thanks!

[@benkozs]

@@JonnyFix There's a dual voltage regulator supplying the 1.25V and 3.3V now the 3.3 is fixed while the 1.25 is set by a zero ohm resistor (tiny black component) which can have intermittent or "high(er)" resistance connections at the solder pads causing the 1.25V to rise. Best to reflow that resistor. In an ideal world there would be a clamping network there to protect the DSP but there isn't so... Anyway good luck with the next one! :)

[@JonnyFix]

@benkozs This exact unit came back, it has been 2 years so that's good. Same chip failure. One of the guys thinks it's when a car sits unused and they don't keep the battery charged. Maybe the sudden drop in B+ when they try start it causes the regulator to go unstable and spike the chip like you mentioned. I also reflowed the reg just in case as I have seen a dry joint under one and that would have same effect as on that resistor to.

[@benkozs]

@@JonnyFix Hmm.. maybe worth putting a clamp on it by using two ZMM1 or similar 0.77V zener diodes in normal series connection on the LDO output to limit it to ~1.5V . In case of a catastrophic failure it may take out the zeners and the LDO but preserve the DSP. Under "normal" momentary overvoltage conditions the LDO and zener should survive if the LDO is short circuit protected internally. BTW you can test the low voltage instability theory on a stabdalone LDO by using your bench PSU to simulate sudden voltage drop in a low enough current limit mode to avoid damage. Or maybe the datasheet mentions something too. Frankly the zero ohm resistor is more suspicious to me though.. I "substituted" it with a healthy blob of solder. :)

[@Live.Vibe.Lasers]

​​@@benkozs​ which zero ohm resistor are we talking about? the one to the left of the bottom output capacitor of the dual voltage regulator at 13:42? or is it the one near the mosfet for the 5v regulator such as at 6:37? Not an EE..barely understand this..just a guy with mediocre soldering skills trying to fix his amp for $7 lol.

[@andyroberts8607]

Hi Jonny , have a BBM2 66 A20 that makes a machine gun/jack hammer sound from all the speakers..... in your experience would this be the codec or DSP ic?

[@JonnyFix]

My experience is limited to these videos :) But it is possible, it could also be the CS42438 codec, if the A/D or D/A sections had failed I suppose it could cause this.

[@alcabins2722]

Same problem in my car did you figure it out andy?

[@skymakai]

Came to your video after finding the driver's side dash speaker wasn't working. I don't know if it's the amp, wiring, or what.

[@brandondiaz7051]

I have a Mazda 3 2018 Amplifier that is not working do you think you can help me out?

[@JonnyFix]

Sorry but I don't have a way to accept jobs from viewers.

[@stevowhitty3984]

Hi I would like to know if you could help me? Do you know what the input signal voltage should be from the head unit

[@JonnyFix]

I do not sorry.

[@stevowhitty3984]

@@JonnyFix no problem thank you

[@zx8401ztv]

I think i would run away from this over complicated nightmare amplifier ha ha :-D Maybe i would nail small leds to the rails so i could see if they were there all the time. It's really odd that the processor ignores the i2c serial memory. I wonder if the chip is actually running at all, stick a radio near that chip to see if its generating a squarewave row like processors often do.

[@JonnyFix]

Well it has oscillator and it gets a little warm, I think something in the chip has failed and it's either lost internal code or the ability to boot from the eeprom.

[@dansbrewing5566]

Sorry do you have the part number / name of this chip? I need to order one 😬😬

[@JonnyFix]

It's just the number on top of the chip. DSPB56374AE

[@jimg3450]

I have one of these that won't give any audio output when the supply voltage goes above 13v. I'm wondering if there is a voltage regulator that has died and some other component is choking on the excess voltage? I was an electronic tech in the Navy but now have no test equip, schematic, etc. Has anyone else seen this? Radio runs fine off the battery but when car is started and voltage rises above 13v then no audio output. Any ideas appreciated.

[@JonnyFix]

That is unusual. How far above 13? All car electronics should be ok up to say 15, an alternator should in theory never put out more than 14.4. Check for AC at the alternator as well as a bad diode can allow ripple through which will upset things.

[@jimg3450]

@@JonnyFix I've got a voltmeter on the power recep. and anything below 13v works fine, above 13v no audio. If it's above 13v and I do something to temp. lower the volts like turn on ac then the audio will turn on for a fraction of a sec.

[@jimg3450]

@@JonnyFix When charging it typically runs about 13.2-13.4

[@jimg3450]

@@JonnyFix fyi, amp was submerged when son drove car into flood water. I already opened the case, cleaned everything, new heat sink compound, etc. but nothing changed. Saw no fried components or anything sketchy. This did NOT change the symptoms. Very odd.

[@JonnyFix]

@@jimg3450 Ah liquid damage, always a curve ball. Could be an SMD ceramic capacitor once they start breaking down they can appear ok then become short after a certain voltage. If you can use a thermal camera or have a feel around you might catch one running warm. I'd also check do you still have the power on signal above 13V that goes to the main reg as we traced out in this video? If yes, is the reg at 6:40 still giving an output? Also output from the reg at 12:00. I've seen them with dry joints, having been wet could have encouraged this more, my first video on these was this. If all rails present and correct while there's no sound then likely an output stage issue, also check the speakers aren't junk from being wet and overloading the amp ICs.

[@mohamedchoukar7366]

Hi jonny, I have one mazda amplifier, i guess same issue. Is there anyone who can fix it for me?

[@JonnyFix]

Check your area for electronics repair services and show them my videos to help them :)

[@DanielVNZ]

@Jonny Fix

[@briant333]

Does the ceramic cap at 25:31 have a crack in it or is it just the light?

[@TheDefpom]

It would certainly warrant an ohms test.

[@JonnyFix]

Tis but a scratch :)

[@emmanuelH.]

Even a gm malibu amplifier.

[@joelgutierrezramos9764]

E compatibile con alfa romeo giulietta

[@brucenicoll4373]

I call them blows