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MicroKorg XL boots but then blank screen and unresponsive

 
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ClearAction



Joined: 05 Feb 2019
Posts: 4

PostPosted: Tue Feb 05, 2019 8:33 pm    Post subject: MicroKorg XL boots but then blank screen and unresponsive Reply with quote

Hi,

First post, I signed up as my keyboard isn't working.

I wonder if anyone can help? My microkorg XL will boot, showing eight blocks under the logo before going blank.

The tempo light flashes but is not responsive to the tempo dial being moved.

If i wiggle the power supply connection, the synth will reboot. Sometimes the reboot behaviour is slightly different (may have a green octave LED lit).

All buttons, keys and switches are inactive when the screen goes blank. I am able to get the keyboard into test mode though, where the buttons are responsive as expected.

This all started after I was playing the keyboard and heard some slight crackling in the audio.

Sounds promising doesnt it!
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OpAmp
Platinum Member


Joined: 07 Jun 2013
Posts: 921
Location: Brussels, BE

PostPosted: Wed Feb 06, 2019 6:05 am    Post subject: Reply with quote

Hi,

Indeed audio cracks can sound promising. Smile

Did you try to play the board using a fresh set of batteries? Just to exclude power supply or the connector?
If that does not help, then probably something is broken.
Did the dsp test work in test mode?
You may need to bring it to a Korg repair service.

Good luck
_________________
microKORGXL, Kaossilator Pro, monotribe, SQ-1, volca fm, Kross 88 BK
Alesis SR18, Akai Miniak, Fender Strat, Line 6 Spider II 112
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ClearAction



Joined: 05 Feb 2019
Posts: 4

PostPosted: Sun Mar 17, 2019 2:35 pm    Post subject: Reply with quote

Hi again and thanks for the reply. I did try the batteries and got the same result. I will try again however, on the off chance that it gives a different result.

What is this DSP test in test mode?

I was thinking I could hopefully figure out which board might be faulty and replace it if one came up in the future...... hopefully if I know a bit more about test mode, I can figure this out?
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OpAmp
Platinum Member


Joined: 07 Jun 2013
Posts: 921
Location: Brussels, BE

PostPosted: Sun Mar 17, 2019 5:47 pm    Post subject: Reply with quote

Hi,

When you are in test mode, it is possible to start something called DSP test. What is exactly does is not clear for me.

The fact that your keys are ok in test mode makes me think that the microcontroller is ok (as they are connected), but that the problem might be in the DSP.
But that is in fact only some guessing/assumption from my side.

Bye.
_________________
microKORGXL, Kaossilator Pro, monotribe, SQ-1, volca fm, Kross 88 BK
Alesis SR18, Akai Miniak, Fender Strat, Line 6 Spider II 112
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ClearAction



Joined: 05 Feb 2019
Posts: 4

PostPosted: Mon Mar 18, 2019 9:27 pm    Post subject: Reply with quote

That was useful, thank you.

I ran the test from test mode, and the keyboard stopped on 'ACK ERR', with flashing lights! :verycool:

The service manual says that this is an 'Audio Clock Signal short or Error' and is part of the DSP check (Codec Reset Check)

If I skip to the next test after the error, it just hangs on the DRO testa nd crashes.

Am I looking at the main board being the problem? Is that where the internal clock chip is?

I think any input on the above will help me decide if it's time to put her out of her misery!

Thanks,

Joe
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ClearAction



Joined: 05 Feb 2019
Posts: 4

PostPosted: Mon Mar 18, 2019 10:22 pm    Post subject: Reply with quote

I have found many replacement DSP chips online

part number tms320vc5501pgf300

I 'think' from looking at the service manual, the audio clock is part of the DSP chipset???

Does anyone think if I replaced this chip, I would have a chance of solving the problem?
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OpAmp
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Joined: 07 Jun 2013
Posts: 921
Location: Brussels, BE

PostPosted: Tue Mar 19, 2019 10:18 pm    Post subject: Reply with quote

Hi,

You are indeed looking at the main board being the problem.

According to me and how I interprete the schematics, the audio clock is generated by the ADC towards the DSP. (sclk and lrclk). The ADC generates it based on the 24,576MHz crystal.

So, before replacing the DSP, I would try first to measure some points. It is not sure that replacing the DSP will solve it.

Bye.
_________________
microKORGXL, Kaossilator Pro, monotribe, SQ-1, volca fm, Kross 88 BK
Alesis SR18, Akai Miniak, Fender Strat, Line 6 Spider II 112
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