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Korg DW-8000 help

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Korg DW-8000 help

Postby Sparrows78 » Thu Apr 22, 2021 10:26 pm

Hi all!
I have gotten my hands on a Korg DW-8000 in great condition. It sounds great, everything works as it should, but after playing it for a few hours the sound cuts out. It gets totally silent, no pops or noises or anything. Everything else continues to work, display, midi, changing patches etc.
The sound comes back when turning the synth off and on again.

Does anyone here have an idea of what might be causing this problem? Any particular thing to look for on the pcb?

Thanks in advance/
Johan
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Re: Korg DW-8000 help

Postby Stickman0_3 » Thu Apr 22, 2021 11:13 pm

Have you had it serviced?
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Re: Korg DW-8000 help

Postby Sparrows78 » Fri Apr 23, 2021 8:33 am

No, it is not serviced yet. I am moderately handy with electronics and used to fix my instruments. I was thinking of recapping the PSU but other than that I’m pretty lost when it comes to this specific problem.
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Re: Korg DW-8000 help

Postby jjlonbass » Fri Apr 23, 2021 9:20 am

The service manual is available here.

The fault may be due to power supply problems, but in my opinion, changing components without diagnosing the problem is a bad idea - if you do fix the problem you will have learned nothing, you may not fix the problem at all and are likely to make mistakes and make things worse.

When the fault appears, do all of the PHONES and L and R outputs go silent?

If the instrument goes totally silent I'd be looking at the muting circuitry to the bottom right of sheet 15 of the service manual, specifically the relay and its control circuit that isolate the output from the delay. Do you have an oscilloscope? If you do, you could take a look at the output of the delay before the muting relay by 'scoping the relay side of R18 and R19 on sheet 15.

John
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Re: Korg DW-8000 help

Postby Sparrows78 » Fri Apr 23, 2021 9:58 am

Thanks for the input, I agree with you about diagnosing the problem.
Yes, both L/R outputs and headphones gets silent.
I did see the muting relay in schematic but have a hard time understanding what can cause it to shut down. I will check with my oscilloscope :thumbup:
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Re: Korg DW-8000 help

Postby Wonks » Fri Apr 23, 2021 10:15 am

Working back from that, using the section 4. block diagram, there are several items which could stop working and then fail to pass on any output signal, the digital delay and the mixer section before it.

Working for a while and then stopping always sounds like a dry joint to me, with contact breaking as the circuit warms up. So I'd do a quick visual inspection of the solder joints and look for anything obvious. But with an oscilloscope you should be able to track back and see if there are any chips with data/signals going in but not out.
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Re: Korg DW-8000 help

Postby Stickman0_3 » Fri Apr 23, 2021 10:20 am

Yes, I would say a dry joint as well. I remember when I had my Sequential Prophet VS, back in the '90's, it was having problems like the ones mentioned. Got it booked in for a service and when it came back it was OK.
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