The No.1 Website for Pro Audio
Korg DW 8000 Repair: Display and Buttons Frozen, Unresponsive, No Audio Out
Old 31st December 2017
  #1
Here for the gear
 

Korg DW 8000 Repair: Display and Buttons Frozen, Unresponsive, No Audio Out

Hello!

I have been trying to get this Korg DW-8000 back in business since purchasing it from Ebay for cheap in an attempt to get one for the synth collection on a budget. The description stated, "Synth powers on but freezes up. I have switched the battery, all tactile switches and firmware eprom but none of this helped the issue. The joystick seems to toggle the parameter settings super fast generating random sound."

When powering the synth on at first i noticed that just about every LED on the keyboard was lit up solid and the display showed an upside down 99. Sometimes when turning it on and off the display will show nothing whatsoever while the arp speed light stays solidly on. When it gets in this state, you have to press the joystick up to get it back into the state with all the lights on. No audio is heard from the outputs when the keys are pressed. Sometimes a random sound will be heard when the joystick is moved around.

After searching through thread after thread I came up somewhat empty handed after trying many different solutions that have been stated. I tried to reset the memory by holding the 5 and 8 key multiple times upon startup and loading the sysex patches only to still see the same unresponsive issue. The battery had been replaced by the previous person working on this keyboard, so I don't think that has to do with the issue at hand.

I took a look at the PSU and saw that there were a few wonky capacitors and the voltage regulators looked like they had some sort of oxidation/corrosion on them. I decided to replace C11, C12, and C19 as well as all the voltage regulators on the PSU. While this did seem to help the voltages on the pins slightly, it didn't seem to remedy the issue at hand.

At this point I am starting to run out of ideas as to exactly what may be the issue here. I am not sure if it is an issue with one of the chips like the RAM, MPU, or CPU, or if it could be a completely unrelated issue all together. Any ideas on this one and some things I could check? I have been using the service manual but am starting to run out of ideas where the problem may lie. Any help would be greatly appreciated. Thanks in advance
Old 11th January 2018
  #2
Here for the gear
 

Hi, you mentioned that you did some repair on the power supply, did you also verify that you are getting the correct voltages on the individual boards? I'm no DW 8000 expert, I've only repaired a couple of them, but when faced with a strange problem like this one, my first step is usually to verify correct voltages to the boards and assorted ICs. You may be getting the correct voltages at the PS, but some other issue like a failed passive component, faulty connector, or damaged board could be causing a voltage problem downstream.

Mark
Old 3rd February 2018
  #3
Here for the gear
 

Quote:
Originally Posted by mratx View Post
Hi, you mentioned that you did some repair on the power supply, did you also verify that you are getting the correct voltages on the individual boards? I'm no DW 8000 expert, I've only repaired a couple of them, but when faced with a strange problem like this one, my first step is usually to verify correct voltages to the boards and assorted ICs. You may be getting the correct voltages at the PS, but some other issue like a failed passive component, faulty connector, or damaged board could be causing a voltage problem downstream.

Mark
Hey I appreciate the reply! I have confirmed the voltages as of recent to be stable and as they should be. I believe that you are correct when you say it probably has something to do with a failed component on KLM 661, so now it is determining just which one it could be.

I tested IC 35 to see if it was firing. I was able to see a square wave on pin 2 for a brief second upon power up before flatlining. The same goes for pin 50 of the same chip. I was able to see some data coming from it for a brief moment before it flatlined. It seems that the CPU is having trouble for whatever reason. I guess next steps would be to check for damages on the board, faulty components, etc? Not too sure exactly what to test for from here other than just removing parts and seeing if they're faulty or not.

Glad I got the power supply under control though
Old 28th July 2020
  #4
Here for the gear
 

So I see it's been awhile since this post was active but I recently acquired a DW8000 for free. When I powered it up the readouts displayed 88 across the board and then went out within 3-5 sec. I am well experienced in electronics troubleshooting and repair but... not so much in the digital arena, certainly not as complex as this unit. However
TS, repair and mods of power supplies, power regulation, vacuum tube and solid state audio amps
I have that covered.
Now back to the DW8000. I verified proper operation of the power supply by verifying proper voltages and stability of all output values. Even so I pulled the 3 primary filter caps and tested their value accuracy and ESR. Amazingly the tested as good as the new Nichicon replacements I had ordered. I changed the internal battery, tested/cleaned all connections, ground points, controls, etc. No improvement over the initial as found response. Note I chose not to reset the processor because No programing tape came with the unit. I decided to check current values at each and all output pins of the PS. I could not find these values online so not sure what they should be.
All registered values under an amp accept pin 3 of connector 2a which was 3.5 - 4.0 amps while maintaining the spec voltage of +5vdc. This seemed to me to possibly be a problem. I used an infrared probe to scan KLM661 and located elevated temperatures in ICs 49-55. These ICs ma be associated with the RAM. No info in the service manual but what little I could find for free indicates they are RAM chips. Note all the chips heating up are identical. Texas Instruments SN74S189.
IC3 (regulator) on the PS board was also registering high temps along with the rectifier.
For this reason, I chose to not probe the 661 board for voltages at individual points for as I say "Releasing the Smoke Monster"
With all this, Did you determine a resolve for your DW?
Thanks Mark
Old 30th July 2020
  #5
Lives for gear
 
acreil's Avatar
 

Quote:
Originally Posted by Marshall Karr View Post
I used an infrared probe to scan KLM661 and located elevated temperatures in ICs 49-55. These ICs ma be associated with the RAM. No info in the service manual but what little I could find for free indicates they are RAM chips. Note all the chips heating up are identical. Texas Instruments SN74S189.
Those store the oscillator frequency and phase information. They get hot but it's no big deal, and a failure there wouldn't cause the problems you're noticing anyway.

I'd look for activity on various CPU bus lines. See if it's scanning the buttons, etc.
Old 4 weeks ago
  #6
Gear Maniac
 
YashN's Avatar
Quote:
Originally Posted by Marshall Karr View Post
Note I chose not to reset the processor because No programing tape came with the unit.
With all this, Did you determine a resolve for your DW?
Don't fret about the lack of 'tape'. This just sends audio-encoded data to the synth.

Take a .wav dump of the factory presets and play it into the synth using a player of some sort, laptop, iphone or what not and take it from there.
📝 Reply
Topic:
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
🖨️ Show Printable Version
✉️ Email this Page
🔍 Search thread
🎙️ View mentioned gear
Forum Jump
Forum Jump