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Help needed. Troubleshooting. No sound! 1 month 3 weeks ago #61482

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I own 2 x PRW-ICE 125.
One of the units had a faulty/mangled RJ-45 port.
So I was not able to get a connection with the network using it.
Therefore I could not use the DSP what so ever...
That had to be fixed.
So I desoldered the RJ-45 port, and soldered in a (seemingly) identical RJ-45 port.

 

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I am disappointed right now.. I no longer get any sound output from the unit ! WHAT?
How....
I did use an ESD armband and have done some PCB soldering work profesionally.
What I get is a very loud 50 hz (?) hum.
Master volume adjustment makes no difference.
There is NO light in the LED chart !
I think there was before the operation
Pushing the "reset" button does not make any difference.
Router seem to assign IP to the thing, but it does not respond to ping.
PWR ICE sofware cannot find it on ethernet..
I am at a loss.
Please advice.
Regards
 

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Help needed. Troubleshooting. No sound! 1 month 3 weeks ago #61489

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Help needed. Troubleshooting. No sound! 1 month 3 weeks ago #61491

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Unit works as expected when swapping in the known-good DSP module from my other unit.
So, it is confirmed that 125ASX2 amplifier module is not at fault.
Before swapping in I did a side-by-side visual inspection of the two DSP modules.'
I can't find any visual defects.


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Help needed. Troubleshooting. No sound! 1 month 3 weeks ago #61492

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But I note that the voltage regulator has been changed on this board.

 

I reckon they discovered it was faulty during a production test, after the robot had assembled the board.

When it hasn't been repaired it looks like this:

 
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Help needed. Troubleshooting. No sound! 1 month 3 weeks ago #61493

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The DSP board doesn't power on.. no LEDs light up.

I confirmed it has power /- 24V.
And I can hear fainth buzzing sound when laying my ear next to the PCB.
(I can't hear that sound on the known-good board).
Frequency seem identical to the one transmitted to the speaker.

I used an ESD bracelet , measured to 1 Mohm, confirmed ground.I worked on a glass surface.. No carpets on the floor..

Is there any help available? Schematics for DSP circuits?
Regards

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Help needed. Troubleshooting. No sound! 1 month 3 weeks ago #61494

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A new RJ-45 port has been soldered in.

 
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Help needed. Troubleshooting. No sound! 1 month 3 weeks ago #61495

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Attempted some measurements to voltage regulators.

First, the power is supplied to the DSP module from aux supply header on the 125ASX2.

 

It is unregulated, so voltage will vary a bit depending on load.
I measured input voltage on both my DSP modules.
The bad board: 23,83 V and -24,0V.
The good board: 23,2V and -23,38V.

(This is consistent with what we know: the bad board doesn't power up like it should.
i.e. it draws less current and it makes sense that its unregulated input voltage therefore sits higher.)
 
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Help needed. Troubleshooting. No sound! 1 month 3 weeks ago #61496

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Googling 78M12G and 7912CD2T we see that these are voltage regulators, designed to give a stable output of around 12 V and -12V, respectively.

78M12G measured within spec. with 11,89V and 11,95V out. Minimum is 11,5V.

7912CD2T also has min. out (-)11,5 V. The bad board measured 10,69 V.. I hoped I was onto something here, but then I measured the known good board, and that measured even lower. 9,87V and 9,80 V. I did all measurements twice. .. I don't know what to think.

Fluke 83 DMM.

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