Problems with DW8000

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westbethkid
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Problems with DW8000

Post by westbethkid » Mon Dec 18, 2006 9:29 am

Hey all, I'm a newbie who just got a used Korg DW8000. It seems to work fine except for two things:

1- the aftertouch doesn't seem to work. As I understand it, when I push harder on the keyboard it's supposed to do vibrato or whatever. I tried changing the appropriate parameters (printed on the far right of the board) but no results...

2- the delay circuit is making a low level "D" tone when active. When I hit a chord on the keyboard, and the delay sounds, the delay has the resulting low level tone accompaning the effect. It's not noticable when the effect level is set from 1-8, but from 9-15 you can hear it, with 15 being the loudest. It is also noticable when using the delay circuit as a chorus. No big deal if you only play D chords!!!

Like I said, everything else works fine...

Has anyone had a similar problem and does anyone have any ideas?

I defer to your collective wisdom and desperately await your prognosis

:?
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westbethkid
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Location: NYC

Post by westbethkid » Mon Dec 18, 2006 10:37 am

Just wanted to add to previous post- when I turn the noise osc. up, that annoying "D" hum is heard again, it's maddening...
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Post by MrHope » Mon Dec 18, 2006 6:16 pm

If i remember correctly, there is a feedback control on the delay. you can also change the delay size, which would change it's tune. reducing the feedback control and increasing the delay size should get rid of the tuned note effect.

All delays can be made to resonate at tunes if their delays are short enough and their feedback levels are high enough.

I don't know about the noise OSC though.

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westbethkid
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Post by westbethkid » Mon Dec 18, 2006 8:26 pm

Hey thanks for responding Mr.Hope-
I turned all the parameters down to 0 on the delay circuit, but it still makes the hum when I break up the effect level parameter. I also noticed that the output switch (high-med) has no effect on the output of the sound. This makes me think
it's something to do with the output circuit. I don't know. I can use it without effects or the noise source, and it sounds good.
I guess I'll have to have a tech look at it, or eat the $200 I paid for it...
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Post by burnt toast » Mon Dec 18, 2006 9:20 pm

after-touch and velocity are often problematic on older keyboards - its to be expected to a certain extent. giving the key contacts a good clean can sometimes help with key related stuff, a lot of muck gets in there over a keyboards lifespan!

not sure about the delay circuit tho, open it up and have a look for any suspect looking components if you are feeling brave or just take it into a shop to get it fixed up. sending it to a repair shop seems like the best idea in this case as it sounds like it could be a bit complex to track down, but theres no harm in having a quick look.

maschingiest might be worth talking to, hes one of the boards resident tech dudes.

good luck!

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westbethkid
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Location: NYC

Post by westbethkid » Mon Dec 18, 2006 10:56 pm

thanks burnt toast-
I'll look under the hood and clean the keyboard contacts- I did notice some notes get stuck sometimes-
should I use compressed air? Or Isopropyl Alcohol?

As far as the hum goes, I guess I can make a visual inspection. Though I'm not much of an techie, I built an Etherwave Theremin from a Big Briar Kit (7 years ago) but it was no picnic. The literature said it could be "built and tuned in an evening." It was a VERY LONG EVENING spanning several days...

anyway, thanks again for the reply, I'll do as you suggest and contact machinegeist
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Post by burnt toast » Mon Dec 18, 2006 11:08 pm

you should only need to use isopropanol/cleaner stuff if theres something nasty and gooey in there. using a slightly damp tissue wrapped around your finger should be enough to get the grime/dust off the contacts - i had a dead key once and it was down to biscuit crumbs or something in there :?:

of course theres no harm in giving it a good clean out with compressed air if it looks nasty in there but its not an essental. i wouldnt assume that compressed air is going to clean the contacts tho - it only removes loose dust. the stuff on the contacts is likely to be squished on there so will need wiping off.

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Post by Maschinengeist » Tue Dec 19, 2006 6:03 am

Sorry. I'm gonna come be back to you on your problems asap.
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Post by Maschinengeist » Wed Dec 20, 2006 4:33 am

Sorry for taking so long. I'm busy as h**l with xmas approching.

Aftertouch: Burnt Toast is right about a good cleaning of the sensors. My prefered method is to use a pencil-type eraser (Steadler) to clean the gold without risk of damage. Clean the rubber and the carbon type too. Maybe the tips need a little carbon touch-up. Never hurts to get all of this clean. I'd have a look at the Aftertouch button too. Sure as h**l it needs cleaning too. Also check the wiring. Could be a problem with the multipler too. But where're getting techie here.

If the cleaning fails to deliver, it gets more serious... like capacitor checks and ICs.

HI/Lo Switch: Could be defective, solder joints could be loose... Could be a component along the way (didn't have time to check it out). And as everything, it leads to the CPU. So while at it check if all chips are firmly seated, that nothing touched them etc. BUT TOUCH BARE METAL BEFORE TOUCHING CHIPS OR WEAR AN ANTI-STATIC WRISTBAND. Static electricity can be deadly for those somewhat fragile components.

Noise: definitely a bad capacitor in the PSU (Power Supply Unit). Visual inspection to see if a capacitor looks bad, burnt or oily. If so replace it by 0.01uF/25V.

If you've got a multimeter at home and know how to use it, check the value of your capacitors.

Have I forgotten something? I wouldn't be surprised.

Hope that helps!

Oh, one more important thing: test the internal battery. Under 2V, scap it and replace with a fresh one. SAVE YOUR PATCHES FIRST!!!

If you don't feel confortable with all this, don't hesitate to see a tech.
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MuzikElektronix.com
Music electronics repair & More
Help? See TechZone
Parts? email!
Service Manuals?+/-2000 documents!
Sorry, they aren't free
Now on FACEBOOK: "Muzik Elektronix"

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westbethkid
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Joined: Mon Dec 18, 2006 8:53 am
Gear: Juno60 SC Six-Trak, Korg Polysix N364 DW-8000 OB Matrix 6 Roland MC-303 SP-202 SP-808 RS09 Yamaha Q-Chord Etherwave Theremin
Location: NYC

Post by westbethkid » Thu Dec 21, 2006 6:47 pm

thanks, maschinegeist-
whether or not I do it myself remains to be seen- but it's great to know what the possibilities are-
you are a lifesaver!
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