# ms-a1004 repaired



## bnae38 (Oct 3, 2015)

Thought I'd share my experience fixing this one.. I'll include pics in future repairs. Doing a miniDsp 6x8 at the moment and have been taking pics. 

Anyways... this is gonna be a long one. 

Acquired schematics here, made things way easier..: http://servicemanuals.pro/servicema...l/car_audio/amplifier/ms-a10041/download.html

Unit cycled in and out of protect when i got it. I popped the top, just 4 screws on back and you have to shimmy the cable bundle past the top board pcb. Then pulled the zif flex loose from press-fit header. I removed the top pcb and noticed the big 22ohm resistor was charred (R3). It ohmed out ok though. 12v comes into it and it feeds q1 which makes 5v for the rest of the pcb. Long story short, I put a 4w 22ohm in there instead. https://www.digikey.com/product-det...ronics-inc/SP3AJT22R0/SP3AJT22R0CT-ND/2665478

Unit appeared to kind of work but then I lost audio on channel 3. The fets were both shorted (Q23 and Q24). https://www.digikey.com/product-det...s-corp/IRF6645TRPBF/IRF6645TRPBFCT-ND/1189865

Okey dokey.. replaced them. And they shorted out again.... 

Replaced the driver chip (https://www.digikey.com/product-det...rp/IRS20957STRPBF/IRS20957STRPBFCT-ND/3738468) and the fets again, and this time they did not blow.

But now I had no audio, and no D carrier on channels 1 and 4......


When removing on re-connecting the wire bundle you NEED to discharge the 35v nets first. Otherwise, you'll keep blowing D driver chips. . I used a 100ohm 2W resistor to discharge the nets to gnd before connecting or disconnecting that header

So at this point, I replaced all 4 driver chips and all was well. (I thought).

Today I noticed some ticking noise coming from my tweets. I figured it was a ground problem, and i was sort of right. When i closed the hatch (which i temporarily have the amps mounted to), the ticking would come and go. Ground loop, I thought. So I connected a wire from the amp base to the car chassis. SNAP. Ok... I measured potential between them and found 32V. Lol.


Pretty self explanatory, the 35v rail in the amp was somehow shorting to the amp chassis. Pretty f'ing lucky i had it mounted on a poor ground source.


Popped it open and found the extender pcb/headers which runs high voltage rails to the middle board was the problem. The back of the bottom connection pins were touching the chassis of the amp. Super design... 

Removed the bottom board this time too, and dremeled off the tops of the solder joints before reflowing them round. Added some kapton to the chassis and the back of the header. 




So I finally got an explanation for what went wrong in the first place. Sorry for the mouthful and I apologize for lack of pictures. If anyone needs help on one of these, let me know.


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## Bayboy (Dec 29, 2010)

Sounds like a headache


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## bnae38 (Oct 3, 2015)

Lol yeah. Somewhat frustrating, somewhat entertaining..


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## Bayboy (Dec 29, 2010)

What's your thoughts on the overall build of it?


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## bnae38 (Oct 3, 2015)

It's not too bad. I like to curse engineers under my breath. Often.....lol. This minidsp had a design problem of sorts too, power inductor touching and shorting to a ground via under it. But yeah, the pin clipping was probably missed at assembly in the jbl.

Heat-sinking is very solid. Resistor on the top board isn't technically under-sized at 2W, but they should have put a bigger one in. The resistor runs friggin hot..

I also disabled the music auto turn-on in hardware, as it doesn't seem to like to save that setting (with it off).


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## bnae38 (Oct 3, 2015)

Removed r74 (300k) to defeat music sense audio turn-on..

Back in the car, running great... As I patiently wait for my 1200.6 to come back..


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## Alrojoca (Oct 5, 2012)

Glad you got yours going.

I had one amp that was replaced by jbl under warranty.

The issue was it did not turn on or it was very erratic. The sense mode was off, and stayed off in my case, but it still failed erratically to turn on, and back on, to the point it just did not turn on, it went on for months getting worse and worse.

I wonder if this has to do with the components you decided to remove or a bad circuit or connection 


Also will a delay, in turning on, would be the beginning of the issue I described before? Or what could be the issue when a delay is there and only when the volume is turned up it turns on, again erratically.


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## Bayboy (Dec 29, 2010)

Oops


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## Alrojoca (Oct 5, 2012)

Yeah that's what I thought, wrong thread, I've done that, but my op was ok asking he original op


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## bnae38 (Oct 3, 2015)

Alrojoca said:


> Or what could be the issue when a delay is there and only when the volume is turned up it turns on, again erratically.



Strange, I'm not really sure if the music sense is turned off. It could be a problem in the main remote turn on circuitry.

I had read about people having issues getting that setting to stay off and I did too. So I just pulled the resistor from the sense cicuit to mico.


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## Alrojoca (Oct 5, 2012)

bnae38 said:


> Strange, I'm not really sure if the music sense is turned off. It could be a problem in the main remote turn on circuitry.
> 
> I had read about people having issues getting that setting to stay off and I did too. So I just pulled the resistor from the sense cicuit to mico.




Thanks, not sure if you came across any specs on the current draw or needed for the remote wires, I am in the process of connecting 3 of these, I was planing to use a relay, but if a new HU top HU from Pioneer can handle the draw for the 3 amps, I will skip using it. Is is it typical for most HU's these days to be able to operate and turn on 3 amps? 

Thoughts ?


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## bnae38 (Oct 3, 2015)

I don't think they spec current draw for the remote, but I don't think it would be much..

You'd probably be fine wiring them all to the HU if they're modern amps.


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