Korg DW-8000 with battery leak damage and repair.

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YashN
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Korg DW-8000 with battery leak damage and repair.

Post by YashN » Thu Oct 27, 2011 9:28 pm

Got this :75: :

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It has several issues:
1. The battery leaked and was removed. There's nothing where the battery used to be right now.
2. There appears to be some acid damage to the circuit just below the battery location (see pic below)
3. Some keys don't trigger notes
4. All notes are the same note (strange thing, first time I come across this)

How would I test the circuit for damage and then repair it?

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Last edited by YashN on Fri Nov 04, 2011 12:14 pm, edited 1 time in total.

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Oooooh!!!

Post by YashN » Fri Oct 28, 2011 8:55 pm

Look what happened today after I spent some time last night opening it up and cleaning the circuit up, and also pushing in the connectors:

http://soundcloud.com/yashn/dw-8000-strings

Only internal DW-8000 effects (delay with lots of feedback, giving it a reverb feel) with Nebula (AlexB TFT console and CDSoundMaster R2R Revox Tape), played from the Kurzweil.

:75: sound fantastic here: 8 stunning analog Korg NJM2069 filters.

Bliss. :guinness:

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Matos
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Post by Matos » Fri Oct 28, 2011 9:11 pm

Yeah! Glad you got it sorted out. Looks like an interesting sound generator. Never heard much about these before.

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Post by YashN » Fri Oct 28, 2011 9:25 pm

Matos, it's the filters my friend. The same one as on the Poly-800, except that as its name doesn't indicate at all, the Poly-800 is actually paraphonic: 8 voices but with a single analog Korg NJM2069 filter (but DCO, i.e. digitally controlled VCOs).

The DW-8000 has 8 of these (but Digital Oscs).

That filter is strong, brash, smooth, creamy, aggressive, lush, superb.

It's in the DSS-1 as well. And some people say it's up there with the best CEMs and SSMs and that it's the best filter Korg ever put in an analog synth.

This, together with the $100 Micron is probably the best value purchase I've ever made.

I'm so happy right now as I nearly thought of putting the NJMs up for sale...

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Post by Matos » Fri Oct 28, 2011 9:39 pm

Ahhhh , the filters. I'm going to have to get my google on and read more.

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Post by dougt » Fri Oct 28, 2011 11:38 pm

Usually lithium batts don't leak like that unless someone installed it backwards or something. Are you sure it's from the battery and not something that spilled into it?

Interesting that you have the all keys playing the same note problem - my EX8000 has the same problem. I thought it might be some invalid patch data but a full reset hasn't solved it.

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Post by YashN » Fri Oct 28, 2011 11:57 pm

Hi Doug,

They are less prone to leakage than the other coin batteries and other non-coin ones, but this one still did. I actually also took the battery from the seller as a souvenir and the greenish residue does come from its edge.

The sounds on the DW-8000 are awesome: lots of superb strings, pads, brasses and clangorous tones too.

Did you try removing the connectors, cleaning them up and putting them back?

Also, try a power on while maintaining 5 and 8 and re-send the patches by SysEx.

Apart from cleaning and brushing the board myself last night and pushing the connector back in, I am not too sure what else I could have done to make it work.

However, the following is something I tried yesterday with all the filters while the Arpeggiator was on, and hence I knew that I would be able to make it work at one point: connect the penultimate pin down on the left to the third pin from the top on the right.

This should be pin 10 to pin 20.

When I did this, I heard the notes arpeggiating correctly, so I deduced that the synth is working correctly up to the voice + filter board and that perhaps the issue was the next board, i.e. the one holding the battery.

I guess the cleaning and brushing gave it the final kick and maybe pushing those connectors too.

I am really, really tempted to try and do an External Audio into VCF mod on this synth. First, I need to get a new battery holder and battery there, and maybe fix some of those non-triggering keys.

An aside:
Thanks to the other DougT's inspiration about salvaging parts this summer, I practised and managed to repair the broken encoder on an Alesis Micron. Desoldering it was a lengthy process, but I had perfected the craft somewhat. :) Thanks. :hail:
Last edited by YashN on Sun Nov 06, 2011 3:56 pm, edited 1 time in total.

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Post by YashN » Sat Oct 29, 2011 12:06 am

That pin 10 to pin 20 connection actually takes the VCA out and feeds it back into the filter input signal Mix #2.

Since I could hear different pitches then, it possibly meant that the voice boards were actually working correctly. The issue must therefore have been elsewhere is what I thought.

Also on my synth, that keybed is the same technology as my resurrected and used JX-8P. I remember botching some key contacts while repairing the aftertouch, and that would make several notes not work.

I wonder if the keybed also had a role on the DW-8000. Most probably it was interfering somewhere. Maybe the residues were short-circuiting something too.

A good brushing with acetone was necessary.

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Post by dougt » Sat Oct 29, 2011 1:08 am

OK yeah I'm sure the problem is on the CPU board not the voice boards. Do you know at what point did you get the correct key pitches back? Was it after you send the sysex dump?

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Post by YashN » Sat Oct 29, 2011 3:56 am

Sometime between last night and tonight and the synth was off the whole day, so it can't have kept any patches.

So I'd say that probably the issue was already gone last night but then I was off to sleep without noticing it or else the issue was gone today when I put it on and had to transfer patches again.

Hard to say precisely, but for sure, transferring patches can help since if there's any memory corruption or erasure, some parameters like 84 will be set to gibberish values.

Keep me posted.

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Post by dougt » Sat Oct 29, 2011 7:21 am

Well I've sent it sysex dumps, cassette dumps, and done resets but no luck.

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Post by LektroiD » Sat Oct 29, 2011 6:24 pm

I'm thinking of selling mine, it's been in my storage room for months, has a great sound but don't have the space for it in my main setup.

I do love the filters, I wonder if anyone has cloned the filter section?

I've seen a few Korg filter clones on modulars, but never a DW8000 clone.

If anyone does a run of these, let me know! :hyper:

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Post by YashN » Sat Oct 29, 2011 8:38 pm

We could 'dive in' together and see where we get and discuss notes, and it will sure be good along the way to get your thoughts about any mods to it e.g. External Audio into the VCF as I did to my Korg Poly-800 except this time, there are 8 filters...

I do need to dive in again since there are non-triggering or stuck keys, so I'll probably have to remove the keybed and work on it completely. I am fortunate that the single note issue seems solved: the synth engine is working perfectly.
dougt wrote:Well I've sent it sysex dumps, cassette dumps, and done resets but no luck.

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Post by YashN » Sat Oct 29, 2011 8:42 pm

Wonderful filters indeed. I've never ever come across a clone. There is at least one instance where somebody took the chip and built a modular filter unit with it, but not a clone. Korg was very secretive on the internals of their filters.
LektroiD wrote:I do love the filters, I wonder if anyone has cloned the filter section?

I've seen a few Korg filter clones on modulars, but never a DW8000 clone.

If anyone does a run of these, let me know! :hyper:

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Post by YashN » Sun Oct 30, 2011 4:30 pm

Doug, here are a few things I would have checked:

1. Battery installed and functioning properly
2. Perform the whole of the adjustment procedure in the service manual
3. If this still does not do it, recap the power supply and repeat steps 1 & 2
4. If this still does not do it, recap the whole boards and repeat steps 1 & 2

It's pushing 25 years, and based on what I've read these past two days, I'd better recap it some day as well.

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Post by YashN » Sun Oct 30, 2011 4:44 pm

The areas between IC47, IC48, IC49, IC50 and the two capacitors above is the area I cleaned thoroughly.

The case is sturdy, mostly metal on the lower case, and mostly plastic on the upper case. On opening, the two sections aren't hinged like the JX-8P, so you are in an awkward position if you want to both dabble with the synth settings and test inside the synth for mods or anything else. I will need to find a way to elevate it sufficiently so that there's enough space for the audio, MIDI and power cables to still be connected without being bent or pressured and be able to put the two parts at right angles or so.

On the docket:
1. Installing a new battery (already purchased, no battery holder for now, so I'll probably do one myself)

2. Inspecting, cleaning and repairing the key-bed (non-triggering, badly triggering notes)

3. Cleaning the switches as they are not acting solidly (bought some cleaning spray with a very small tube)

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Last edited by YashN on Fri Nov 04, 2011 12:17 pm, edited 1 time in total.

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Post by fonik » Sun Oct 30, 2011 5:11 pm

yes, the filters! i have a DSS-1, and he filters make it sound special. the DCO's are common 12bit, so it is obvious to me.
i even thought of buying another DSS-1 just to salvage these ICs - alas, this might break my heart, since i love the DSS-1...

oh, YashN: awesome job you do!
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Post by YashN » Sun Oct 30, 2011 8:01 pm

Here you are again, after I just replied to you on the other forum ;) Great minds, great minds.

I love this filter, Fonik, love it, love it.
oh, YashN: awesome job you do!
Barely, barely, but thanks. I was quite close to envisioning extracting the filter chips and selling them separately. Heaven made it so that after some cleaning and connector-pushing, it's aliiiive!

I want to fix it as much as possible and then plan some enhancements to it, with the help of Doug and other knowledgeable brothers-in-synth-diy-arms.

Last night I cleaned up the upper plastic casing and rubbed hydrogen peroxide on the keys. You wouldn't imagine the amount of greasy dirt on that casing and the grime on the keys. Or, since you may have bought some second-hand equipment yourself, you would imagine exactly how it is!

I think I have become something of a nostalgic old man, because seeing poly analog synths mistreated like this makes me sad. People don't know the value of these instruments.

And yes I know the DW-8000 uses digital oscs, but it's a polyphonic analog/hybrid with real analog filters, and those filters... wait till I manage a realtime Cutoff Frequency and Resonance mod on it, it will scream. There's a reason the original mod on the Poly-800 is called the Moog Slayer. While some would argue it wouldn't slay any Moog, I would argue it would be better called a 'Speaker Slayer' or an 'Amp Slayer'. This filter, with the mods, wants to kill other equipment.

So, to recap (no pun intended :P ) it's a bit sad how people dismiss these instruments (yes they are machines, but also instruments, to make music, with beautiful, beautiful sounds), but it's also a newly welcome blessing in my life, as I discover and re-discover the joys of analog (or hybrid) electronic synths and manage to obtain them at bargain prices.

Here is also the moment to thank the other DougT again for his inspiration about salvaging parts and building one's own synth - I came across his blog this summer while thinking about building my own modular synth and learned to salvage parts and desolder parts. This helped build confidence and was knowledge and practical experience which came in handy when repairing my broken Micron bought used.

So, with this thread, I am hoping to perfect my own knowledge of synth DIY and repair, as well as help others including Doug if possible since his issue was one of mine of the DW-8000, and perhaps plan some mods to the DW-8000. Wouldn't that be awesome and beautiful to have been inspired and helped on this journey and to be able to inspire and help others in return?

Here are some pics of it after partly cleaning the plastic upper cover with glass cleaner and wiping the white keys with Hydrogen Peroxide. The black keys still need to be cleaned. You can see the cleaning spray with the tiny precision tube as well as the replacement Maxell CR2032 3V coin battery.

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Tonight, I'll tackle the keybed and switches if possible.
fonik wrote:yes, the filters! i have a DSS-1, and he filters make it sound special. the DCO's are common 12bit, so it is obvious to me.
i even thought of buying another DSS-1 just to salvage these ICs - alas, this might break my heart, since i love the DSS-1...
Last edited by YashN on Sun Nov 06, 2011 3:56 pm, edited 1 time in total.

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In case you doubt that this battery can leak.

Post by YashN » Tue Nov 01, 2011 1:39 am

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That should clear any doubt about the capacity of this battery to leak and damage the board. I am not sure it's the original battery but it could be: a Sanyo Li-Mn.
Last edited by YashN on Tue Nov 01, 2011 3:14 am, edited 1 time in total.

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Switch cleaning

Post by YashN » Tue Nov 01, 2011 1:48 am

I used a canister of Nexxtech "Contact and Head Cleaner". Relatively expensive as everything at The Source. Should have bought the canister at the small shop a few streets away.

Composition:
  • Isopropanol
    Isobutane
    Butane
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Spray between the switches and around them while the synth is on, and click the switches in turn until they work well.

Note: do not spray this on the faders. You'd need a cleaner with lubricant for these.

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Note the white residue left on the upper panel. This suggests that this mixture is actually not that good of a cleaner, since if the same residue accumulates between contacts, it can decrease their efficiency when dry.
Last edited by YashN on Tue Nov 01, 2011 2:52 am, edited 2 times in total.

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Removing the keybed.

Post by YashN » Tue Nov 01, 2011 1:58 am

Now, this synth is unhinged, unlike the interior of the Roland JX-8P as previously mentioned. So, there's no way to hinge it properly when open and keep it powered while accessing the upper panel.

Things are totally different when the keybed is removed as you will see. Then the parts can be set up in all sorts of easy configurations.

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Labeling the keyboard cables and cutting them free (not cutting them...)

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Check whether you labeled every cable. I had missed one.

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The keybed is unscrewed and removed.

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The synth is tested keyboard-less and still works.

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This is just one way you can position the Keybed, connect it again with the synth open. To be able to do this, you need to unscrew the small keybed PCB:

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Keybed cleanup Part 1.

Post by YashN » Tue Nov 01, 2011 2:04 am

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Spraying between the middle and lower contact, I cleaned all of the keys.

To clean the other contact, press the key and then spray between the middle contact and the upper contact.

Here I reached another milestone as all keys started triggering when tested this time. Hurray!
Last edited by YashN on Tue Nov 01, 2011 2:22 am, edited 1 time in total.

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Battery DIY replacement

Post by YashN » Tue Nov 01, 2011 2:10 am

Bought a Maxell 3V CR2032 and didn't manage to get hold of a coin battery holder.

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I soldered two thin wires I extracted from an ethernet-type cable to the board, red for positive and black for negative.

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These leads were cut long enough so that I could route them both through a single heat vent slit in the lower case and still have some length to spare outside.

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Since I have nothing better for now, I taped the two wires to the new replacement battery and put the whole into the original plastic container of the Maxell CR2032.

This whole new contraption is then taped to the middle of the lower case which is slanted, in such a way as this ultra DIY 'solution' is not very visible, but is easily accessible if there is a need to replace the battery again.

Transferred Data over via SysEx, turned off the synth, turned it on again and all programs were still available.

Battery mod successful.
Last edited by YashN on Tue Nov 01, 2011 2:24 am, edited 1 time in total.

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Adjustment Procedures.

Post by YashN » Tue Nov 01, 2011 2:13 am

Found the DW-8000 service manual online and performed some of the easy adjustment procedures verification. I don't have an oscilloscope handy nor a digital voltmeter.

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Adjustment mode 2, final key test and cleanup.

Post by YashN » Tue Nov 01, 2011 2:21 am

In Adjustment mode 2, the green LED screen will change every time a key is hit. This is useful to diagnose all keys, together with sound if possible.

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During this final test, I mark the dodgy keys which sometimes get stuck or which sometimes have some trouble triggering or which trigger with a lower velocity using a removable marker:

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I repeated the contacts spraying procedure until I was happy with:
1. All keys triggering
2. No keys get stuck on ON
3. All keys have velocity working properly
4. All keys triggering and effecting aftertouch properly.

Success!

In the following picture, you can see layers of grime and yellowing. I cleaned this with Hydrogen Peroxide.

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